Thursday, August 6, 2009

Chill Out With Delosperma

Delosperma is a delightful evergreen ground cover that only came to my attention within the last few years. It is a succulent, low-growing perennial plant that lends a fresh, cool appearance even during hot weather. These plants are becoming widely known mostly due to the work of Dr. Panayoti Kelaidis of the Denver Botanic Garden.

Delosperma (pronounced del-o-SPUR-ma), commonly called "ice-plant" is native to South Africa where it grows in moderate to dry soils even in high mountain areas. Nevertheless it does nicely in much of the U.S. in climate zones 5 through 9.

The name, Delosperma, means "obvious seed", for they are rather large in relation to the rest of the flower. The common name, "ice plant", refers to the watery, succulent appearance and the icy green color of the foliage, along with other plant properties.

Delosperma is suitable for ground covers, rock gardens, alpine gardens, cactus and succulent gardens, hanging baskets, sunny perennial gardens and borders when planted with species having similar requirements.

There are about 14 species of Delosperma, but only a few are readily available commercially.

Delosperma basuticum thrives in USDA climate zones 5 through 9. Some report success into zone 11. Though I haven't been able to confirm this, I believe the species is named for Basotho, (now known as Lesotho) a region in south Africa where it is native. Maximum height is 3". Yellow to white flowers are produced all summer and into fall. It needs well-drained garden soil with pH ranging from slightly acid to slighty alkaline. It is drought tolerant. Mature plants grow to 12" across. It will produce a beautiful carpet in optimal conditions. Plant in full sun. Space at 8" to 12".

Delosperma cooperi is named for Dr. James G. Cooper(1830-1902), conchologist, geologist, ornithologist, zoologist. Dr. Cooper contributed a great deal to understanding the geology, flora and fauna of the Pacific Northwesst.

D. cooperi, also known as Trailing Ice Plant or Hardy Ice Plant, thrives in USDA climate zones 5 through 9. Flowers are pink to magenta.

D. x 'Mesa Verde', also known as D. x 'Kelaidis', is a new cultivar resulting from pollination by Dr. Kelaidis, mentioned before. It is well-worth seeking. 'Mesa Verde' has been reported to do well in USDA climate zones 4 through 9.

Delosperma nubigenum, which shares its common names with D. cooperi, is similar in habit to D. basuticum and D. cooperi. "Nubigenum" means "born in clouds", referring to its high-altitude native habitat. One might think that it preferred only cool climates, but it also thrives in USDA climate zones 5 through 9 or 10. Flower color is yellow.

Prepare the planting bed for Delosperma by cultivating at least 6" deep, removing all traces of weeds. Take a soil sample to your nearby Cooperative Extension Service office for testing. Follow their recommendations. Compacted soil should be cultivated to 10" deep. Composted manure may be incorporated into the soil. Fertilizer may be used. If you choose to do so, incorporate fertilizer per the soil test recommendations, or 5-10-15 fertilizer at a rate of no more than 2 lbs. per 100 square feet, into the top 4" to 6" of soil. Avoid synthetic fertilizers contacting any part of your plants.

Container-grown Delosperma can be planted any time you have a shovel handy, but may require monitoring of soil moisture conditions during hot weather. But Delosperma is very forgiving.

Space plants 8" to 12" apart, as indicated earlier. Keep in mind that my spacing recommendations are approximate. If you want them to fill in quickly, plant closer together. If you have plenty of time and patience but less money, plant them farther apart. Dig planting holes into the cultivated soil a little less deep than the depth of the growing container. Place the plants into the holes and back-fill. Press soil around the roots. Do not cover the root balls with soil. The tops should be slightly exposed. Add a top-dressing of mulch around the plants, not on top of them, about 2" to 4" deep. Irrigate thoroughly.

Maintenance is minimal. A little weeding and occasional watering should do the trick.

For a low-maintenance, low-growing colorful groundcover that is drought-tolerant, consider Delosperma.

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