Bourreria radula – Rough Strongbark

Rough strongbark is a Florida state-listed endangered plant with significant wildlife value. It is a large shrub or small tree with small, dark green leaves whose upper surface has coarse, rough hairs that give the leaves a sandpaper-like texture. Attractive and sweetly fragrant white flowers are borne nearly year around and these are much sought after by various insects, including bees and butterflies. The flowers are followed by rather large, highly ornamental, orange berries that are eaten by birds, raccoons, opposums, and other animals.

Rough strongbark occurs as a native plant in Florida only in the Florida Keys but it can be grown at least as far north as Palm Beach County and probably much further north if it is not grown too far from the moderating influence of the Atlantic Ocean or the Gulf of Mexico. Its cultivation presents few problems so long as it is provided with well-drained rocky or sandy soil and abundant sunlight. Once established, rough strongbark is extremely drought tolerant and even small plants have readily established themselves in the driest part of my garden. Propagation from cuttings and seeds is difficult; however, with time, numerous self-sown seedlings will appear under mature plants and these can be potted up when they are a few inches high. Since rough strongbark readily sprouts from the roots wherever the roots are cut or injured, it can probably also be propagated from root cuttings.

Rough strongbark is extremely tolerant of hot, dry conditions and poor, alkaline soils. Thus, it is useful as a landscape plant or hedge in difficult urban situations such as roadsides and parking lots. The abundant fruits falling on sidewalks can make quite a mess and it is not recommended as a residential street tree, although it is otherwise an excellent street tree.

Image and text © 2013 Rufino Osorio

Bastardiopsis eggersii – Jost Van Dyke's Indian-Mallow

Jost Van Dyke's indian-mallow is a highly endangered Caribbean shrub or small tree known from three islands in the British Virgin Islands and one island off the coast of Puerto Rico. An article by Fred Kraus provides very detailed information about this rare plant. The image above is of a young plant growing in a private garden in Fort Lauderdale, Florida. The plant is surrounded by numerous seedlings of black ironwood (Krugiodendron ferreum). The genus to which Jost Van Dyke's indian-mallow belongs has been a matter of some controversy and it is sometimes found listed as Abutilon virginianum or as Sida eggersii.

Plants in my garden flower in early spring (January in south Florida). The flowers are tiny but are attractive to bees and are rather pretty when examined closely.

Images and text © 2013 Rufino Osorio

Ficus aurea – Native Strangler Fig

Ficus aurea was named for its pale green leaves with yellowish veins, resulting in a "golden" appearance.

The scientific name of the native strangler fig, Ficus aurea, literally means the golden fig, and here it is, looking very golden indeed, at the Juno Dunes Natural Area in Palm Beach County. Although typically found growing in tropical hammocks and the edges of mangroves and swamps, it sometimes occurs, quite unexpectedly, in sand scrub.

It is a remarkably easy native tree to grow from seeds or cuttings and it is tolerant of a wide variety of cultural conditions. However, it has an invasive root system that will quickly find, and clog, septic systems as well as leaky pipes or sewers. Thus, it should never be cultivated anywhere in the vicinity of septic systems, plumbing, and sewers.

Image and text © 2012 Rufino Osorio

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.