A Xeric Garden

A dwarf agave with rosettes less than 12 inches wide toughs it out in pure Florida sand. My guess is that it is one of the many forms of Agave potatorum. The genus Agave is native to the New World from the southern United States to South America but it reaches its greatest diversity in Mexico.

I have been watching the endeavors of a local gardener with keen interest. Apparently having grown weary of tending a lawn, this gardener removed all grass from a small front yard and is growing tough desert plants. Although markedly different from the typical pseudo-tropical south Florida garden, it shares with such gardens the presence of plants from far-flung regions of the world and a lack of any native plants.

Euphorbia tirucalli is native to Madagascar and is characterized by a highly toxic and caustic sap. It has also been linked with Burkitt's lymphoma, a typically rare cancer that tends to be associated with regions where Euphorbia tirucalli is extensively used as a hedge plant. The pictured plant is a cultivar with brightly colored new growth called 'Sticks on Fire.'

An Opuntia species with a growth habit similar to the native semaphore cactus (Opuntia corallicola); however, the native semaphore cactus is markedly spiny and tends to have pads of a lighter green color.

The so-called Madagascar palm is not a palm at all. It is Pachypodium lamerei, a spiny-stemmed succulent from Madagascar in the oleander family (Apocynaceae). It should be handled with care since the spines are extremely sharp and can cause severe injuries or infections if they happen to impale the knuckles or joints of the fingers.

This aloe is very similar to Aloe arborescens from Africa; however, the rosettes are much smaller than that species. I am guessing that perhaps it is a small-growing hybrid of Aloe arborescens.

Images and text © 2012 Rufino Osorio

Opuntia humifusa – Common Prickly-Pear

Opuntia humifusa, the most common prickly-pear in Florida as well as in eastern North America.

These prickly-pear fruits added an unexpected bit of color on a January hike at the Juno Dunes Natural Area in Palm Beach County, Florida.

Image and text © 2012 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.

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.

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.