Plant of the Week 08/28/2006: Sprenger's Asparagus-fern (Asparagus aethiopicus)

Plant of the Week 08/28/2006

Sprenger's Asparagus-fern (Asparagus aethiopicus)

Asparagus aethiopicus Linnaeus

Photographed by: Chelsie Vandaveer
Credits: Sprenger's asparagus-fern, an unwanted volunteer in personal garden.
Other Information: Olympus C-8080wz

Sprenger's asparagus-fern (Asparagus aethiopicus Linnaeus) is native to South Africa. The species epithet refers back to the time when all of Africa, outside of Egypt and the Mediterranean coastal lands, was known as Aethiopia (Ethiopia) by the Romans. Since Linnaeus named the plant in 1767, it has received a multitude of other names—Asparagopsis densiflora, Asparagus densiflorus, Asparagus sprengeri, A. densiflorus cv. Sprengeri, even Protasparagus aethiopicus. The common name, Sprenger's, honors a little known botanist-gardener who managed Kaiser Wilhelm's (William II) garden on Kerkyra (Corfu).

Asparagus are Monocotyledons, that is, its seed germinates with a single cotyledon or 'seed leaf'. By some taxonomic authorities the genus is in its own family, the Asparagaceae, and includes around 350 species. Others divide the family into three genera. And by still others place Asparagus in the Liliaceae, the lily family.

Although a common houseplant, Sprenger's asparagus-fern is unusual. The linear 'leaves', each with a single vein and arranged in clusters, are really cladodes or modified stems. The true leaves are reduced to small bracts along the main stem. These bracts do not photosynthesize; that function is carried out by the cladodes. The bracts do have a function; they contain calcium oxalate crystals and harden with time becoming spine-like. Browsing animals and unwary weeders learn quickly the power of these bracts.

The asparagus-fern blooms when the stem attains maturity. Kept in a hothouse, this can be any time of the year; outside in the south, this is usually summer to fall. It produces a raceme of tiny greenish-white, white, or pinkish-white flowers. Each tiny flower has six tepals and six stamens and gives rise to a green berry that ripens red. The berry often holds 6 or more seeds.

The berries are the problem. Birds are attracted to the fruit and spread the seeds. In Florida, parts of Australia, and many Pacific Islands, Sprenger's asparagus-fern has become an exotic pest plant displacing native plants. And it is not a plant to put into a landscape, at least, not in the South. A neighbor tried to remove a large clump planted by the previous owner. Two broken shovels and a broken pickaxe later, the plant was hauled from the ground. And the photographed specimen, well, it volunteered to grow under an oak and has been dug out twice!

(Compiled from: Hortus Third, Staff L.H. Bailey Hortorium, NY College of Agriculture and Life Sciences, Cornell University, Macmillan, NY, 1976; "Asparagaceae", L. Watson and M.J. Dallwitz (1992 onwards), The Families of Flowering Plants: descriptions, illustrations, identification, and information retrieval, Version 29 July 2006.; w3 Tropicos, VAST, Jim Solomon, Missouri Botanical Garden; and "Asparagus aethiopicus", Wunderlin, R. P., and B. F. Hansen. 2004. Atlas of Florida Vascular Plants Institute for Systematic Botany, University of South Florida, Tampa. [S. M. Landry and K. N. Campbell (application development), Florida Center for Community Design and Research.].)