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

References:

• 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).

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

 

References:

• 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.

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.

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).

References

• 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 (http://plants.usda.gov, 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).

References

• 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.

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

References:

• George, H. 2010. Insects That Make Cyanide. suite101.com. 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.