The Cactus Patch
THE NEWSLETTER OF THE BAKERSFIELD CACTUS & SUCCULENT SOCIETY
Volume 6       January 2003      Number 1

Notes on Haworthia
by L. M. Moe


Haworthia emelyae
photo by L. Maynard Moe
The plant of the month for January is Haworthia, a group of small succulent perennial monocot herbs confined in the wild almost exclusively to the Republic of South Africa. They are related to lilies (see below) and look like miniature aloes but, unlike aloes, have small 2-lipped white flowers. Haworthias are all rosette shaped succulents, although some have rather grassy leaves (e.g., H. longiana). Some can add leaves until they are somewhat columnar (H. venosa and H. glauca), while others remain as flat rosettes. Some of the most popular Haworthias have translucent 'windows' at the end of their leaves (H. truncata, H. retusa, H. emelyae - see photo of H. emelyae from my outside garden) where photosynthesis occurs inside the leaf that is filled with a translucent jelly.
Charles Duval gave this group of plants the name Haworthia in 1809 to commemorate Adrian H. Haworth, an English entomologist and botanist who specialized in succulents. Since then, Haworthia nomenclature has been continuously changing, fueled by how different clones of the same plant can vary according to their growing conditions, and by the ease by which many species interbreed. In the literature there are over 400 species named, but currently these have been reduced to about 60 species with about 100 subspecies.

Haworthias rarely require a pot larger than 4 inches in diameter making them ideally suited for a bright windowsill. Although some haworthias are more difficult to cultivate than others, most are very easy to grow. They require abundant bright light, but need light shade to shade to grow well. They also require a well drained soil that approaches dryness between watering. It is best to fertilize only sparingly (only during active growth, not at all if the plant is resting) using a water soluble house plant fertilizer diluted to 1/4 strength.

Propagation for many species is done easily by separating offsets. For others that offset slowly or not at all, seeds are the best way to propagate. Leaf cuttings are possible for some of the species (generally those with thick leaves).


Haworthia cymbiformis var. transiens
photo by L. Maynard Moe
A note on taxonomy: In the past, Haworthias, Aloes, Gasterias, and their relatives were treated as a tribe in the Liliaceae, a huge family of monocots that also included lilies, onions, agaves, and yuccas. All of these plants have colorful petals, arranged in threes, and six stamens.

More recently, botanists have discovered phytochemical and molecular evidence that shows this concept of Liliaceae to be artificial and unnatural (meaning that it does not conform to evolutionary relationships).

Haworthia venosa ssp. tessellata
photo by Stephen Cooley
A more accurate classification, one that is based on all available characteristics, reveals that the old "Liliaceae" are best classified into two major groups (or orders, in taxonomic parlance) - the LILIALES and the ASPARAGALES. Lilies, Trilliums, and a few others are in the Liliales. Onions, agaves, yuccas, haworthias, irises, and orchids are placed in the Asparagales. Within the Asparagales there are several families, two of which include succulents - the Agavaceae (Agaves, Yuccas) and the Asphodelaceae (Aloes, Gasterias, Haworthias, and Bulbines). Some experts on succulent plants tend to recognize the haworthias, gasterias and aloes, all of which are especially succulent, in a separate family - Aloaceae. Whereas, the professional taxonomic botanists tend to recognize the larger family, based on molecular data, and call it the Asphodelaceae.

A good internet site for Haworthias is maintained by the Haworthia Society
which embraces the genera Aloe, Astroloba, Gasteria, Haworthia,
related small genera and Bulbine together with their hybrids and cultivars.

A site with many good photographs can be found at:
www.haworthia.com/Species/Haworthia.htm

Two good books are:
The Illustrated Handbook of Succulent Plants: Monocotyledons edited by Urs Eggli
Haworthia Revisited by Bruce Bayer
(both are in our library).

If you have any comments or questions or would like to
submit a photograph or article, contact

thecactuspatch@aol.com

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