Sunday, December 12, 2010



The plant pictured above is a beautifully grown succulent in the stonecrop family (Crassulaceae) at Abell's Nursery in Lake Worth, Florida. It is probably a hybrid with at least one parent being a Graptopetalum, a genus native to North America, where it ranges from Arizona to Oaxaca, Mexico.

The plant in the upper left corner of the photograph is Portulacaria afra, a member of the portulaca family (Portulacaceae) native to Africa. It is represented by two distinct forms, the typical green-leaved form and a form with variegated leaves.

© 2010 Rufino Osorio.

Saturday, December 11, 2010

Tithonia rotundifolia

Tithonia rotundifolia

Tithonia rotundifolia (Miller) S.F. Blake is an annual native to Mexico and Central America. Depending on the plant's genetics and growing conditions, it grows 3–6 feet tall. It is grown for its large, brilliant orange-red daisies, these being used as cut flowers or as a source of nectar in butterfly gardens. The plant is a serious invasive pest plant in some countries but it is not regarded as invasive in the United States, where it has sparingly escaped cultivation in Florida and Louisiana.

In my garden, plants of Tithonia rotundifolia were severely attacked by various insect pests and a plant virus almost as soon as they germinated and the severely weakened plants barely survived long enough for me to obtain the photograph above before promptly dying without setting seeds. In view of this plant's invasive tendencies in various tropical and subtropical regions, I did not consider its early demise in my garden unfortunate.

© 2010 Rufino Osorio.

Stokesia laevis – Stokes-Aster

Stokesia laevis, stokes-aster

Stokesia laevis (J. Hill) Greene is a perennial wildflower in the daisy family native to Alabama, Florida, Georgia, Louisiana, Mississippi, and South Carolina. It grows 1–2 feet tall and is distinctive for its large lavender-blue daisies which are borne in June–September. In nature it occurs in woodland openings, bogs, and wet flatwoods and savannas; however, it readily adapts to garden conditions in light shade to full sun in sites with rich, moist soil. Plants slowly form rather large clumps and it is easily propagated by division of the clumps. It may also be propagated from root cuttings and from seeds, which do not require any special pretreatments for germination. There are reports that seeds of stokes-aster may germinate irregularly over a long period of time (Gettys & Werner 2001); however, in one experiment, 78% of 985 seeds germinated within 42 days (ibid).

Stokesia laevis, stokes-aster


  • Gettys, L.A. and D.J. Werner. 2001. Stratification unnecessary for germination of seeds of stokes aster [Stokesia laevis (J. Hill) Greene]. Proceedings of the Florida State Horticultural Society 114:250–251. PDF


© 2010 Rufino Osorio.

Thursday, November 11, 2010

Lindernia microcalyx

Lindernia microcalyx Is not native to the United States. It is included here as an aid to identification and not to promote its cultivation.

Lindernia microcalyx

Lindernia microcalyx Pennell & Stehl is an annual or short-lived perennial native to the tropics of North and South America. I found it growing in a somewhat disturbed wet area in Martin County many years ago; however, I did not send voucher specimens to any herbariums so it is not officially listed as an introduced species occurring outside of cultivation in Florida. It is distressingly similar to the native Lindernia grandiflora in its sprawling stems that root wherever they touch moist soil, in its rounded leaves, and showy flowers. It differs in having (1) minutely glandular hairy sepals; (2) thickened pedicels, often noticeably thicker just below the seed capsule; (3) flowers self-fertile with every flower setting a seed capsule, even in isolated plants; and (4) subglobose seed capsules about 2 millimeters long. In contrast, the native Lindernia grandiflora has non-glandular, hairless sepals; filiform pedicels of uniform thickness; usually self-sterile flowers with isolated, solitary plants rarely setting seeds; and seed capsules 4–5 millimeters long.


© 2010 Rufino Osorio.

Monday, November 8, 2010

Ipomoea ternifolia var. leptotoma

Ipomoea ternifolia var. leptotoma

Ipomoea ternifolia var. leptotoma

Ipomoea ternifolia var. leptotoma is a desert ephemeral native to Arizona and Mexico. It is horticulturally distinctive in its delicate, lacy leaves, which are divided into 3 or 5 narrow lobes; the rapidity with which it produces abundant flowers; and the striking violet-lavender color of its relatively large flowers.

Desert ephemerals are annuals that are adapted to brief periods of heavy rains and they are remarkable for the speed with which they flower and set seeds. Ipomoea ternifolia var. leptotoma, for example, will flower within a few weeks of germination. As the desert soil dries after heavy rains, the plant begins to die but even dying plants that have lost all their leaves will continue to produce flowers and set seeds so long as the stems remain green. Since desert ephemerals have no water-storing succulent roots, stems, or leaves, there is great urgency to set seeds before the last vestige of moisture is gone and extended hot and dry conditions return to the desert. The plants then lie dormant, in the form of seeds, awaiting the next period of heavy rain.


© 2010 Rufino Osorio.

Sunday, November 7, 2010

Glycosmis parviflora

Warning: Glycosmis parviflora has a very high potential of becoming an invasive pest plant. It should not be cultivated in the warm-temperate, subtropical, or tropical regions of the United States and all occurrences outside of cultivation should be promptly destroyed. It is included here only as an aid to identification and not to promote its cultivation in any way whatsoever.

Glycosmis parviflora
Young potted plant only 19 inches (0.5 meters) tall but freely flowering and fruiting.

Glycosmis is a genus of approximately 50 species of unarmed shrubs or trees in the citrus family (Rutaceae) native to eastern, southern, and southeastern Asia, with a few species also in Australia. The genus can be distinguished from all other members of the citrus family in Florida, both native and introduced, by the following combination of traits: (1) plant unarmed and lacking spines; (2) fruit a fleshy berry; and (3) terminal and axillary buds, and often the young inflorescences, covered with tiny rust-colored hairs or scales.

Glycosmis parviflora
Close-up of an axillary bud covered with tiny rust-colored hairs.

One species, Glycosmis parviflora (Sims) Little, has become established outside of cultivation in the United States, where it has been recorded from Broward and Miami-Dade counties and the Monroe County keys. Originally native to China, Taiwan, Japan, Myanmar, and northeast Vietnam (Dianxiang & Hartley 2008), it was introduced into the United States as a curiosity of ethnobotanical interest and as possible genetic material in the breeding of citrus fruits (Wiersema & León 1999:243). Plants identical to Glycosmis parviflora appear in a wide variety of internet sites under the name Glycosmis pentaphylla; however, every instance of Glycosmis pentaphylla that I have seen on the internet shows images of a plant with leaflets that have entire or slightly wavy margins, which are typical of Glycosmis parviflora. In contrast, Dianxiang & Hartley (2008) state that the leaflets of Glycosmis pentaphylla have toothed (serrated) margins.

Glycosmis parviflora
The species epithet, parviflora, means tiny flowers.

Glycosmis parviflora displays the following attributes that are associated with invasiveness: (1) Young plants are shade tolerant; (2) plants begin flowering and fruiting when less than two feet tall and less than three years of age; (3) plants are self-fertile and abundantly produce fruit, even when growing in isolation; (4) in warm regions, flowers and fruits are borne throughout the year; (5) relatively pest free; and (6) fruit dispersed by vertebrates (birds and mammals). Although it is not presently listed as an invasive plant, it should be watched closely and all occurrences outside of cultivation should be promptly destroyed.


  • Dianxiang, Z. and T.G. Hartley. 2008. In Z.Y. Wu, P.H. Raven, and D.Y. Hong (eds.) Flora of China: Volume 11. Science Press (Beijing) and Missouri Botanical Garden (St. Louis). Internet PDF
  • Wiersema, J.H. and B. León. 1999. World Economic Plants: A Standard Reference. Boca Raton: CRC Press.


© 2010 Rufino Osorio.

Cuphea glutinosa

Cuphea glutinosa

Cuphea glutinosa is a short-lived South American perennial that has been found outside of cultivation in wet ground in Louisiana and Texas. The plant has sprawling stems and forms a small groundcover several inches tall and about one-half to one square foot in extent. The small flowers are about half an inch in diameter but are showy and conspicuous because of their bright violet-pink color. It was rather popular for a brief period among collectors of cottage-garden-style plants but it has been eclipsed by taller and showier Cuphea species and hybrids and it is now very rarely available in horticultural commerce. This is perhaps not unfortunate given its propensity to establish itself in sunny areas with moist or wet soils.


© 2010 Rufino Osorio.

Asclepias curtissii

Asclepias curtisii

Curtiss's milkweed is a state-listed endangered species with specialized habitat requirements. It is found almost exclusively in scrub habitats where it tends to favor areas of pure sand with very little vegetation. It is remarkable in that it is one of the few plants that readily colonizes areas of pure sand at the edges of stable blowouts.

Geologically, a blowout is a depression in a sandy habitat caused by strong winds. Blowouts get their start when some disturbance, such as fire, extended drought, off-road vehicles, or human or animal foot traffic, results in the loss of protective vegetation. Sometimes, a positive feedback cycle forms where the blowout causes plants to die along its periphery, this makes the blowout bigger, and this in turn causes more plants to die, resulting in an ever expanding area of pure sand devoid of any vegetation.

Curtiss's milkweed occurs as a native plant only in the State of Florida. Within the state, it has a wide range and has been recorded in many counties from Clay County in the north to Broward and Collier counties in the south; however, it is endangered in spite of its wide distribution because of its exacting habitat requirements and habitat loss.


© 2010 Rufino Osorio.

Friday, November 5, 2010

Passiflora lutea – Yellow Passion Vine

Passiflora lutea

Yellow passion vine is a perennial vine that climbs by means of tendrils and has stems that can reach 3–5 meters (10–16 feet) in length. It favors shady, moist woodlands and forests but is remarkably adaptable so long as it is not subjected to long spells of hot and dry conditions. The leaves can vary from solid, dark green to pale green, often with beautiful, silvery variegations on the upper surface, as seen in the image above of a plant obtained from Meadow Beauty Nursery. The tiny flowers are only about 1.5 centimeters (half an inch) in diameter and are nondescript from a distance; however, they reward close examination due to their intricate and delicate structure.

As with other native passion vines, yellow passion vine may be profitably grown in butterfly gardens, where its leaves are used as a caterpillar food plant by gulf fritillaries (Agraulis vanillae), julias (Dryas julia), and zebra longwings (Heliconius charitonius). This interesting native vine also has a remarkable association with a highly specialized bee, the passiflora bee, Anthemurgus passiflorae. It is a small black bee whose females collect, as the sole food source for their larvae, only the pollen of yellow passion vines (Neff 2003).

I once attended a lecture by a butterfly gardener who stated that "we should grow pretty passion vines since they are all equal as far as the butterflies are concerned." By this, she meant that we should grow large-flowered passion vines and ignore the small-flowered native passion vines. But she was wrong on two counts. First, some non-native passion vines are lethal to the caterpillars that normally feed on native passion vines, so it would make a difference to the butterflies whether or not a passion vine is native. And it would make a big difference to specialist insects such as the passiflora bee, whose progeny would starve without the native yellow passion vine.

Yellow passion vine is botanically interesting as the most cold-hardy and northern growing of any passion vine native to the Western Hemisphere. It occurs as a native plant only in the United States, where it has a considerable range that includes much of the eastern half of our country.

USDA Distribution Map


  • Neff, J.L. 2003. The passionflower bee: Anthemurgus passiflorae. Passiflora 13(1): 7–9. Internet


© 2010 Rufino Osorio (exclusive of the USDA map).

Thursday, November 4, 2010

Peperomia humilis

Peperomia humilis

Florida is the only state in the continental United States with native Peperomia species. Eight occur in Florida, two non-native species and six native species. Of the native species, all but one are rare, state-listed endangered plants (Wunderlin & Hansen 2008). Peperomia humilis A. Dietrich is the Florida native species with the greatest geographic range and it occurs in 12 counties from Duval County in the north to Collier and Miami-Dade counties in the south.

Peperomia humilis is fairly common in cultivation among Florida native plant gardeners and is moderately easy to grow. Optimum requirements are a brightly lit but shady spot in well-drained soil that does not dry out excessively. Failure to successfully cultivate this plant is most commonly due to overwatering it or planting it in poorly drained soils. As with most peperomias, it makes an ideal houseplant so long as the soil is allowed to become almost completely, but not quite, dry between waterings and it is not located in a very hot, dry spot.


  • Wunderlin, R. P., and B. F. Hansen. 2008. Atlas of Florida Vascular Plants. Institute for Systematic Botany, University of South Florida, Tampa. Internet


© 2010 Rufino Osorio.

Sunday, September 19, 2010

Youngia japonica

Warning: Youngia japonica is an extremely pernicious non-native weed. It is included here only as an aid to identification and not to promote its cultivation in any way whatsoever.

Youngia is an Asian genus of about 30 species of annuals and biennials (or rarely perennials) in the daisy family. One species, Youngia japonica, is now a pantropical weed established throughout the warmer parts of Africa, Europe, Asia, Australia, Pacific Islands, and North and South America (Spurr 2006). Youngia japonica has been reported in the United States from every Gulf state as well as Arkansas, the District of Columbia, Hawaii, Kentucky, Maryland, North Carolina, Pennsylvania, South Carolina, Tennessee, and Virginia. Its presence as far north as Pennsylvania is perhaps indicative of significant cold tolerance and it may well become a truly cosmopolitan weed.

Youngia japonica forms a basal rosette of lobed leaves somewhat reminiscent of dandelions but it differs by its branched inflorescence, which bears one or two leaves and carries several to numerous small flower heads resembling tiny dandelions. The fruit is a one-seeded cypsela crowned by a tuft of stiff hairs that aid in dispersal by the wind. It is a remarkably adaptable plant and can grow in any moist site in full shade to full sun. It is usually not found in dry areas but it will tolerate considerably dry soil if situated in a shady spot.

Youngia japonica grows especially well in the pots of ornamental potted plants, both in gardens and commercial plant nurseries, and a single plant can quickly multiply into thousands, infesting every pot throughout an entire nursery. When such potted plants are shipped elsewhere, Youngia japonica is also inadvertently spread to new locations. For example, the first time I saw this species was in a specialty nursery in Chicago, where potted plants had been shipped in from Florida. All it would take is for the nursery owners to place the pots outdoors for the summer and it is likely that yet another non-native weed would soon be established in Chicago.

Once it builds up to a large population, Youngia japonica is extremely difficult to eradicate because even depauperate plants only an inch tall can flower and set seed, and such tiny plants are easily overlooked while weeding. In addition to being a nursery and garden weed, Youngia japonica is a common and tenacious lawn weed.

USDA Distribution Map


  • Spurr, P.L. 2006. Youngia. pp. 255–256. In Flora of North America Editorial Committee (eds.) Flora of North America: Volume 19. New York and Oxford: Oxford University Press. Internet
  • USDA, NRCS. 2010. Youngia japonica. The PLANTS Database. Baton Rouge: National Plant Data Center. Internet

© 2010 Rufino Osorio (exclusive of the USDA map).

Saturday, September 18, 2010

Orthemis ferruginea – Roseate Skimmer

Orthemis ferruginea - Roseate Skimmer
Image © 2010 by R. Hopper. Used with permission.

This striking image of a male roseate skimmer, Orthemis ferruginea, was taken by Rob Hopper. The roseate skimmer is a dragonfly found in the southern United States, from where it extends south to Brazil and east into the islands of the Caribbean.

Text © 2010 Rufino Osorio.

Silybum marianum – Blessed Milk Thistle

Warning: Silybum marianum has been listed as an invasive pest plant or noxious weed. It is included here only as an aid to identification and not to promote its cultivation in any way whatsoever.

Flowering plant in coastal California sage scrub. © 2010 Joseph Libertucci. Used by permission.

Silybum marianum is a biennial or winter annual originally native to the Mediterranean regions of Europe, western Asia (Israel and Turkey), and northern Africa (Egypt). It is now widely established outside of cultivation as a weed in tropical and southern Africa, northern Europe, the British Isles, Australia and New Zealand, and North and South America. It is readily identified by the spiny leaves that are conspicuously variegated, as well as by the flower heads, which are subtended by bracts whose tips expand into a leafy, spine-tipped appendage.

Foliage of young plant. © by Valérie75 2006. Used under a Creative Commons license.

Milk thistle seed extract (silymarin) has shown promise in the treatment of liver diseases, cancer, hepatitis C, HIV, diabetes, and high cholesterol, as well as protective effects against liver damage by poisonous mushrooms; however, there have been few high-quality randomized clinical trials to conclusively prove the therapeutic effects of milk thistle (see, for example, Tamayo & Diamond 2007).

Seedling. © by Beentree 2008. Used under a Creative Commons license.

Silybum marianum was touted as an ornamental garden plant in the 1980s and seeds were widely available from mailorder garden catalogs; however, its popularity has waned as gardeners realized that it dies after flowering and they must then deal with a large mass of dry and wickedly spiny foliage. It is still widely sold as an herb garden or medicinal plant but the therapeutic properties are contained in seed extracts and such extracts are easier to purchase ready-made than to make at home from seeds harvested in the garden. In several states, Silybum marianum is an invasive pest plant or a declared noxious weed. Thus, in view of its weedy nature as well as its toxicity to livestock, its cultivation should not be encouraged.

USDA Distribution Map



  • Tamayo, C. and S. Diamond. 2007. Review of clinical trials evaluating safety and efficacy of milk thistle (Silybum marianum [L.] Gaertn.) [abstract]. Integrative Cancer Therapies 6(2): 146–157.
  • USDA, ARS, National Genetic Resources Program. Silybum marianum. Germplasm Resources Information Network - (GRIN) [Online Database]. National Germplasm Resources Laboratory, Beltsville, Maryland. Internet

Text © 2010 Rufino Osorio. All images copyrighted by their respective owners as indicated above.

Sunday, September 12, 2010

Crotalaria pumila – Low Rattlebox

Crotalaria pumila is an annual or short-lived perennial that generally grows up to about 12 inches tall and about as wide or wider. It has alternate leaves with each leaf divided into three segments. The flowers are bright golden yellow with usually some red streaks, the streaks being especially pronounced on the back of the banner petal. Flowers are soon followed by inflated light brown pods with loose seeds that rattle when the pods are shaken. The plant does not spread vegetatively; however, the pods eventually split open with great suddenness and ballistically hurl the seeds several feet away from the parent plant.

The principal horticultural uses are as a small ornamental wildflower, as a low groundcover, and as a butterfly garden or insect garden plant. Two groups of insects are attracted to Crotalaria pumila: the foliage is used by the caterpillars of the cassius blue butterfly and the bella moth (a beautiful day-flying moth with white wings banded with orange-pink spots), while the flowers attract small native bees, which serve as the principal pollinators. Plants are very easily grown in any open, sunny spot with well-drained soil and the seeds germinate within a few days if the hard seed coat is lightly nicked or scratched between two sheets of sandpaper.

Crotalaria pumila: has a remarkably wide range that includes Florida as well as the western United States. It has also been reported from Maryland, and it has been introduced on the Hawaiian Islands. Outside of the United States, it occurs in both the Lesser and Greater Antilles and from Mexico south to Paraguay and Argentina.

USDA Distribution Map


© 2010 Rufino Osorio (exclusive of the USDA map).

Funastrum clausum

Funastrum clausum is a vigorous vine with long stems capable of climbing to great lengths. It is commonly known as white twine-vine or white milkweed-vine and is usually associated with wet areas such as ditches, pond margins, and the edges of mangroves and swamps. The plant is tolerant of disturbance and is occasionally found in overgrown thickets in old empty lots and along railroad tracks. It has a variety of horticultural uses and can be grown in a moist, sunny area wherever a vigorous, freely flowering vine is desired. It is also highly recommended for insect and butterfly gardens since the sweetly fragrant flowers attract a wide variety of insects and the foliage is eaten by the caterpillars of monarch, queen, and soldier butterflies.

Funastrum clausum is native to Florida and Texas in the United States. Outside of the United States, it occurs throughout a very wide area from Mexico to Argentina, as well as in the Caribbean.

Until recently, this plant was known as Sarcostemma clausum and it is still found under that name in many publications and web sites.

© 2010 Rufino Osorio.

Sunday, August 29, 2010

Forest Quote

Although it is composed of trees, the forest is far more than a collection of trees standing in one place. It has a population of animals and plants peculiar to itself, a soil largely of its own making, and a climate different in many ways from that of the open country. Its influence upon the streams alone makes farming possible in many regions, and everywhere it tends to prevent floods and drought. It supplies fuel, one of the first necessaries of life, and lumber, the raw material, without which cities, railroads, and all the great achievements of material progress would have been either long delayed or wholly impossible.
– Gifford Pinchot

Dodonaea viscosa – Varnish Leaf

Plant in flower. © 2007 by Forest and Kim Starr. Used under a Creative Commons license.

Dodonaea is a small genus of approximately 70 species of woody shrubs or small trees with alternate (or rarely opposite) simple or pinnate leaves. About 60 species are confined to Australia, about nine more occur in Africa, the Americas, and Asia, and one species, Dodonaea viscosa, is pantropical and occurs as a native plant on all continents except Antarctica and Europe. In Florida, Dodonaea viscosa is known as varnish leaf, a reference to the shiny, sometimes sticky, resinous coating on the leaves. It is remarkablly adapted to harsh coastal environments where it tolerates moderate salt spray, wind-blown sand, strong winds, and intense sunlight. Although usually growing as a small shrub up to 3 meters (10 feet) tall, in Hawaiian forests it is sometimes a tree up to 9 meters (30 feet) tall. Varnish leaf is characterized by alternate, simple, elliptic-shaped leaves; greenish flowers that are mostly either male or female on separate plants; and inflated, papery, 3-celled and 3-winged capsules that hold a few rounded, black seeds. The capsules are green when young, changing first to pale green and then gradually to various shades of pink, red, brick red, or purplish red, and eventually to light brown at maturity. Depending on growing conditions, temperature, and the plant's genetic background, the reddish color can be intense and may produce a highly ornamental effect.

Dodonaea viscosa is remarkable for its fast growth, general freedom from pests and diseases, and ability to thrive under highly varied conditions. In Florida, it is restricted to coastal strand and coastal hammocks but elsewhere in its range it grows in extremely diverse habitats. For example, in Hawaii it is found in "coastal dunes, lava fields, [and] dry, mesic and wet forests" (Anonymous 2009). Its altitudinal range in Hawaii is as impressive as the variety of habitats in which it occurs and it can be found in lowlands at 3 meters (10 feet) of elevation all the way up to subalpine shrubland at 2,347 meters (7,700 feet) (Little & Skolmen 1989). In the United States, in addition to to Florida, it occurs as a native plant in Arizona where it is described as "fairly common on dry, rocky slopes and in canyons, often on limestone" (Kearney & Peebles 1951:528). In California, it has been recorded from Orange County (USDA, NRCS 2010).

Drawing from Little & Skolmen 1989, a U.S. Government work (as republished by the University of Hawaii at Manoa 2003).

Varnish leaf is easily grown from seeds, although patience is required since germination rates may vary from a few weeks to several months. Propgation may also be effected from shoots with half-ripe wood taken in the summer (Plants for a Future 2010). Due to its rapid growth and ease of cultivation, varnish leaf is highly recommended for beginning gardeners in USDA plant hardiness zones 9–11 and it can generally be expected to succeed so long as it is provided sufficient water during establishment and is situated in an area with ample sunshine and well-drained soil. It is admirably suited for coastal gardens where many other plants find life difficult but it will also grow well inland. Due to its fast growth, evergreen leaves, and tendency to freely branch, it is perhaps most often used as a hedge or screen but it may also be profitably grown as a specimen plant, foundation plant, and in coastal and tropical hammock restorations. In addition to the wild form with bright green leaves, there is a popular purple-leaved cultivar that is extensively cultivated in the United States; however, plants of this cultivar that I saw in San Francisco seemed less vigorous than the green-leaved plants I am familiar with in Florida. Varnish leaf has very few faults only two of which are fairly serious. Occasional plants may become black from mildew growing on the sugary secretions of mealy bugs and scale but this situation is easily remedied by cutting the plant to the ground, after which it soon sprouts new, pest-free shoots that can attain their former height within a year. Another problem is that plants can become a big, floppy messs if provided with too much water or if planted in very rich soil.

Besides it ornamental uses, varnish leaf has numerous medicinal uses although such practices are not recommended since the leaves contain cyanogenic compounds, tannins, and saponins, all of which are toxic in sufficiently high quantities. The conspicuous capsules are both reminiscent of hops and have been used as a substitute for hops to add a bitter flavor to beer, thus accounting for another of its common names, hop bush. It is of considerable biogeographic interest in that it "and wingleaf soapberry ... Sapindus saponaria, are the only tree species native in both Hawaii and continental United States" (Little & Skolmen 1989).


  • Anonymous. 2009. Native Plants of Hawaii: Dodonaea viscosa. University of Hawaii. Internet
  • Kearney, T.H. and R.H. Peebles. 1951. Arizona Flora. Berkeley and Los Angeles: University of California Press.
  • Little, Jr., E.L. and R.G. Skolmen. 1989. Common Forest Trees of Hawaii (Native and Introduced). Agriculture Handbook No. 679. Forest Service, United States Department of Agriculture (as republished by the University of Hawaii at Manoa, 2003). Internet
  • Plants for a Future. 2010. Dodonaea viscosa. Internet
  • USDA, NRCS. 2010. The PLANTS Database (, 29 August 2010). Baton Rouge: National Plant Data Center. Internet

© 2010, except as noted, by Rufino Osorio.

Harrisia fragrans – Fragrant Prickly-Apple

Harrisia fragrans is a rare, federally-listed endangered cactus of sandy coastal areas and recorded from Volusia, Brevard, Indian River, and St. Lucie counties along the east coast of peninsular Florida. It is now extremely rare in the wild and it has been reduced to approximately 320 plants in St. Lucie County (Possley 2010), with all other occurrences having been eliminated as a result of habitat destruction. The prospects for this plant appear dim since the wild populations show high death rates for mature plants and low rates of recruitment and establishment for seedlings (Rae & Ebert 2002).

The plant is characterized by narrowly columnar stems with 10–12 ribs and growing 3–5 meters (9.8–16.4 feet) long. Such lengths appear to be the result of plants trying to grow above the surrounding vegetation since cultivated plants in full sun tend to remain much shorter. Young shoots are very showy as a result of the bright yellow spines that contrast beautifully with the dark green stems. The spines darken as they age but even on very old stems, the spines will usually retain yellow tips.

Disproportionately large, fragrant, white flowers are produced in late spring and these quickly develop into huge, rounded, orange-red fruits that take several months to ripen. The fruits are sparsely covered with small scales and are filled with numerous seeds embedded in a mildly sweet white flesh with a pleasing flavor. Fruits can be cut in half and the flesh and seeds scooped out and eaten in the same manner as kiwi fruits and, like kiwi fruits, the flavor can be enhanced by adding a squeeze or two of lime. Plants are equally ornamental in flower and in fruit and the latter are "a great attraction as food for birds, many of whom are ravenously fond of the seeds" (Small 1932 quoted in Parfitt & Gibson 2003).

Harrisia fragrans is very easily cultivated from seeds and young plants about two years old and only 30.5 centimeters (12 inches) tall will readily flower and set fruit in a small pot. Plants are also easily propagated by stem cuttings that have had their cut ends allowed to dry for a day or two and then inserted into sandy soil. If one has the room, it should be grown in large groups where quantities of large white flowers will present a very attractive sight and many fruits can be produced, to the gastronomic delight of the gardener, assorted mammals, and birds.

Harrisia fragrans, under the name Cereus eriophorus var. fragrans, was formerly treated as a variety of Harrisia eriophorus; however, the latter is now regarded as an exclusively Caribbean species that differs in its 8–9-ribbed stems and longer, black-tipped spines (Parfitt & Gibson 2003).


  • Britton, N.L. and J.N. Rose. 1920. The Cactaceae: Descriptions and Illustrations of the Cactus Family. Volume II. Washington, D.C.: Carnegie Institution of Washington Publication No. 248. Internet
  • Parfitt, B.D. and A.C. Gibson. 2003. Harrisia. pp. 152–153. In Flora of North America Editorial Committee (eds.) Flora of North America: Volume 4. New York: Oxford University Press. Internet
  • Possley, J. 2010. CPC National Collection Plant Profile: Cereus eriophorus var. fragrans. St. Louis: Center for Plant Conservation. Internet
  • Rae, J.G. and T.A. Ebert. 2002. Demography of the Endangered Fragrant Prickly Apple Cactus, Harrisia fragrans [abstract]. International Journal of Plant Sciences 163(4): 631–640. Internet
  • Small, J. K. 1932. Harrisia fragrans—fragrant prickly-apple. Addisonia 17: 29–30.

A plant that survived hurricanes Frances and Jeanne in 2004 produces new shoots in the spring of 2005.

Image published prior to 1923 (Britton & Rose) and now in the public domain. Text © 2010 Rufino Osorio.

Saturday, August 28, 2010

Centaurea scabiosa – Greater Knapweed

Warning: Centaurea scabiosa has a high potential of becoming an invasive pest plant. It is included here only as an aid to identification and not to promote its cultivation in any way whatsoever.

Centaurea scabiosa Linnaeus is native to Siberia and Europe (USDA, ARS 2010) and is distinguished by its deeply lobed leaves and flower heads borne singly at the ends of the stems. The flower heads are subtended by broad, usually pinkish or purplish bracts with the margins fringed at the apex. The outer florets in each flower head are spreading, enlarged, and neuter (that is, sterile and not producing seeds). The plant is a perennial with thick, woody rootstocks that form a large, conspicuous rosette of leaves early in the year and from which arise flowering stems 1–3-feet tall, with the flowers present from July to August or September. Within its natural range, it favors chalky or limestone soils and the image above was taken by John Jordan in "south-west England on the edge of Salisbury Plain, a chalky hillside which used to be grazed pasture many years ago, but is now common land trimmed once a year." Ecologically, it is notable for attracting a wide variety of nectar- and pollen-seeking insects; as the sole source of food for the caterpillars of the case-bearing moth, Coleophora didymella Chrétien; and, in Britain, it is usually the only host of the parasitic plant, knapweed broomrape (Orobanche elatior Sutton) (Rumsey & Jury 1991:267). Besides greater knapweed, the plant is also known as greater centaury, hardhead, and ironhead, the latter two common names being a reference to the hard, solid flower heads (Grieve 1971:456).

Greater knapweed is now well established in Canada and throughout a wide range in the northern United States. Although it is definitely weedy, it is not currently listed as ecologically invasive in North America; however, due to the tendency of Centaurea species to become invasive pest plants in the northern United States and Canada, its cultivation should not be encouraged and plants growing in the proximity of natural areas should be closely observed and eliminated if seen to be spreading at the expense of the native flora. Greater knapweed might be mistaken for spotted knapweed, Centaurea stoebe L. ssp. micranthos (Gugler) Hayek (Centaurea maculosa auct. non Lam.), which is an invasive pest plant, since both plants have deeply lobed leaves. However, the latter has much smaller flower heads up to 1-inch wide, whereas greater knapweed has larger flower heads that are 2 inches wide or wider.

Observant readers may have noticed the red-spotted black moth at the base of the flower head. It is a burnet moth in the genus Zygaena, a group of day-flying moths that sequester cyanogenic glucosides from various members of the pea family that serve as food for the caterpillars, although George (2010) reports that these moths can also manufacture cyanogenic glucosides and do not need to obtain them from the larval food plants. The boldly patterened wings are an example of aposematic coloration, which is also known as warning coloration and serves as a visual cue to predators that the moth is distasteful and toxic.

USDA Distribution Map


  • George, H. 2010. Insects That Make Cyanide. Internet
  • Grieve, M. 1971. A Modern Herbal, Volume 2. Mineola, New York: Dover Publications. Internet
  • Rumsey, J. and S.L. Jury. 1991. An account of Orobanche L. in Britain and Ireland. Watsonia 18:257–295. Internet
  • USDA, ARS, National Genetic Resources Program. 2010. Germplasm Resources Information Network (GRIN) Online Database. National Germplasm Resources Laboratory, Beltsville, Maryland. Internet

Image © 2010 by John Jordan and used by permission. Text © 2010 by Rufino Osorio.

Where Can I Obtain Florida Native Plants?

I am frequently asked where one may obtain Florida native plants. So, I thought it was about time I provided a detailed answer. If you would like to know my "secret" sources, go over to the Florida Native Plant Society's blog where I have written a post on sources for Florida native plants.

Monday, August 16, 2010

Hypoxis decumbens

Hypoxis decumbens is a grassy plant that bears small, brilliant yellow flowers. It is easily grown from seed and the plant in the above image was grown to full maturity in a small 2-inch (5-cm) plastic cup in an east-facing window.

It is native throughout a very wide range in Mexico, Central America, the Greater and Lesser Antilles, and South America.

© 2010 Rufino Osorio.

Ludwigia maritima

Ludwigia maritima is a perennial wildflower found in all coastal states from Louisiana to North Carolina. It occurs in flatwoods, bogs, and swamps but, as far as I can tell, it has no connection whatsoever to the sea or to maritime habitats and its species epithet, maritima, which means of the sea, is a bit of a mystery. It is very common in Florida, where it has been recorded from every county except Gadsden, Gulf, Indian River, Lafayette, Monroe, Pinellas, Santa Rosa, Suwannee, and Washington counties. Like many other native herbaceous wildflowers, it is almost unknown in cultivation in spite of being a remarkably graceful plant with slender branching stems that bear showy flowers over a very long period of time.

As is typical of Ludwigia species, it is extremely easy to grow and plants will flower during their first year when grown from seeds. Its cultural requirements are modest and it will happily grow in a pot or in the ground so long as it is provided with moist soil, bright light, and freedom from taller plants. Although adapted to wet soils, the stems arise from deep-seated subterranean tubers and, if subjected to drought, the plant will go dormant and come back from the tubers when conditions improve.


© 2010 Rufino Osorio.

Monday, August 9, 2010

Asimina reticulata

The pineland pawpaws were magnificent this year and many plants were covered with flowers. This one was growing in a sand scrub nature preserve right smack in the middle of urban coastal south Florida approximately 10 minutes from my house by car.

© 2010 Rufino Osorio.

Sunday, August 8, 2010

Ant dispersal in Aristolochia serpentaria (Virginia snakeroot)

Aristolochia serpentaria - Virginia Snakeroot

Myrmecochory, the dispersal of seeds by ants, is a common adaptation among perennials growing in mesic forests, and the principal characteristic of seeds dispersed by ants is the development of the elaiosome, an oily, nutritive appendage that is attractive to ants. Allard (2002:4) reported that the seeds of Aristolochia serpentaria did not exhibit any specialized adaptations for dispersal and that they lacked an elaiosome. However, neither statement is correct as is indicated in the above photograph of a recently opened capsule of Aristolochia serpentaria. Note that the seeds are attractive to ants and that each seed is provided with a large, creamy-white, fleshy elaiosome. Although seemingly small relative to the size of the seeds, these ants were eventually able to remove all but one of the seeds from the capsule.

Dried Aristolochia serpentaria seeds, as might appear on an herbarium sheet, do not display signs of an elaiosome, which in this case quickly dries and shrivels up. It is thus easy to conclude that Aristolochia serpentaria is not adapted for dispersal by ants; however, the cultivation of this plant in pots, which makes very close observation possible, reveals myrmecochory and adds Aristolochia serpentaria to the long list of forest wildflowers with ant-dispersed seeds.


Allard, D.J. 2002. Aristolochia serpentaria L. (Virginia Snakeroot) Conservation and Research Plan for New England. Framingham, Massachusetts: New England Wild Flower Societ. Retrieved on 8 August 2010 from

© 2010 Rufino Osorio.

Sunday, August 1, 2010

Opuntia abjecta

Opuntia abjecta

Opuntia abjecta

Note: This article was originally titled Opuntia triacanthos; however, molecular genetic analysis by L.C. Majure (2012) indicated that it cannot be O. triacanthos because the Florida plants fall into a separate clade than does O. triacanthos from the Caribbean. Majure's research showed that O. abjecta is a distinct species originally distinguished by John Kunkel Small.

Opuntia abjecta is a Florida state-listed endangered species, under the misapplied name of O. triacanthos, that is remarkable for its small size and it slowly forms low mounds that will cover about two square feet and reach 3–6 inches in height in a few years. Previously, Florida's population was thought to be an outlier of the Caribbean species, O. triacanthos. But it is now known to be a distinct species, first recognized by John Kunkel Small, that is endemic to the Monroe County Keys.

Opuntia abjecta

The pads are very weakly attached to one another and this, in combination with the barbed spines, means that they will almost leap onto the shoes, clothing, or fur of anyone or anything that brushes against the plant. Thus, it should not be situated where animals or people will pass nearby. This is not only for the benefit of passersby, but for the plant itself since the frequent loss of pads causes the clumps to fall apart and they will not flower as freely as undisturbed clumps.

This interesting miniature succulent is well worth growing in succulent plant collections. If one lacks a garden, it can be grown as a potted plant, and I have flowered it in a 3-inch pot on a south-facing windowsill.

Majure, L.C. 2012. The Evolution and Systematics of the Opuntia humifusa Complex. University of Florida doctoral dissertation. 10 May 2015.

© 2009, 2015 Rufino Osorio. All rights reserved.

Saturday, July 31, 2010

Pokeweed—An Overlooked Native Plant

Pokeweed is one of the most common plants throughout much of the United States and has been recorded from all but 12 states. In Florida, it has been recorded from all but 8 northern counties—and chances are that it occurs in those counties but has merely been overlooked. Perhaps because it is so common, it is often ignored as a garden plant. Additionally, it is frequently described as a coarse and homely plant but such assessments are more a reflection of the writers' prejudices than they are an accurate description of pokeweed.

Botanically, it is known as Phytolacca americana and it is the only temperate-zone member of a small, mainly tropical family. Pokeweed is a big, bushy perennial that can grow up to 10 feet in height but plants in natural communities with low nutrient soils rarely exceed 3 feet in height and width. It has stout, fleshy, pink stems and large, elliptic, dark green leaves but is otherwise rather unremarkable in appearance. Small, white flowers are produced in long spikes, which vary from rigidly erect to gracefully pendent. The flowers are followed by dark purple berries with beautifully contrasting rose or red stalks. The combination of rose-red and dark purple is a magnet for a wide variety of birds, which avidly seek out and eat pokeweed berries. An image of a yellow-breasted chat whose ventral area has been stained purple from eating so many pokeweed berries may be seen at the Hilton Pond web site. In colder areas, such as northern Florida, the berries persist on the plant for many months and they are an important winter food source for birds when other foods are unavailable or scarce.

As is to be expected from a common plant that frequents areas affected by human disturbance, pokeweed is simplicity itself to grow and asks for nothing more than dry to moist soil in full to partial sun. The stems arise from thick, tuberous roots and if the tops are destroyed by drought, hurricanes, insect hordes, or human pruning, new shoots will arise in due course when conditions improve. Since I rarely water my garden, my pokeweed plants rarely exceed two feet in height and maintain themselves as compact masses of green accented by white flowers and purple berries. New plants are easily grown from seed but patience is required since seeds sometimes take a few months to germinate. Select forms are easily propagated vegetatively by dividing the tuberous roots.

In addition to its horticultural and wildlife uses, pokeweed is famous as the source of poke sallet, a spinach-like green prepared from young shoots up to 12-inches tall that have been boiled in at least two changes of water. It is extremely important that poke sallet never be prepared from shoots that include any parts of the roots or that show any tinges of pink or rose color. These precautions and extensive pre­pa­ra­tion are necessary since all parts of the plant, but most especially the roots and older shoots, are toxic to human beings. Although the berries are also toxic, they are not dangerously so and, to this day, their juice has been used to add vibrant color to jams and jellies. Rural children used the berries' juice as ink but today’s children, reared on television and computers, are oblivious to such simple enter­tainments. The sliced roots, fried in bacon fat, have been fed to dogs to rid them of intestinal worms, but this is a dangerous practice and it is preferable that parasite-infested pets be taken to a veterinarian.

As is the case with so many plants, pokeweed has found greater acceptance outside its native home and has long been grown in Europe and Asia, where it is popular both for its edible shoots and as an unusual accent plant in perennial borders and shrubby foundation plantings. The time to welcome this interesting native to American gardens is long overdue and pokeweed deserves a place in every native Florida garden that can accommodate its modest needs.

Solenostemon scutellarioides - Coleus

Solenostemon scutellarioides - Coleus

The common garden coleus can be highly invasive in moist or wet tropical forests.

© 2009 Rufino Osorio. All rights reserved.