High Country Gardens, Drought Tolerant Plants, Xeriscape Perennials

How to use cold-hardy plants from South Africa in the western US garden.

Item # 42410	Diascia integerrima 'Coral Canyon'® Coral Canyon® Twinspur each $5.49 3 to 6 plants $5.29 7 or more $4.99 Qty:

Item # 39725	Delosperma cooperi Hardy Purple Ice Plant each $5.49 3 to 6 plants $5.29 7 or more $4.99 Qty:

Item # 38910	Cotula sp. ‘Tiffindell Gold’ Creeping Gold Buttons each $5.99 3 to 6 plants $5.79 7 or more $5.59 Qty:

Item # 57852	Hirpicium armeriodes v. armeriodes Grassleaf Mat Daisy each $5.99 3 to 6 plants $5.79 7 or more $5.59 Qty:

Item # 14510	Aloinopsis spathulata Hardy Living Stone each $5.99 3 to 6 plants $5.79 7 or more $5.59 Qty:

Item # 81000	Rabia albipuncta Frilled Flower Hardy Living Stone each $5.49 3 to 6 plants $5.29 7 or more $4.99 Qty:

Item # 92949	Nananthus transvaalensis Transvaal Ice Plant each $5.49 3 to 6 plants $5.29 7 or more $4.99 Qty:

Item # 83750	Ruschia pulvinaris Creeping Shrubby Ice Plant each $5.49 3 to 6 plants $5.29 7 or more $4.99 Qty:

Item # 99532	Cold Hardy South African Succulent Sampler Sampler $28.44 Qty:

Item # 95605	Titanopsis calcarea Concrete Leaf Living Stone each $5.49 3 to 6 plants $5.29 7 or more $4.99 Qty:

• Topic: Cold Hardy Gardens
• Author: David Salman
• Keywords: flora, climate, exotic plants, South Africa, Garden Design, gardens
• Date: April 2002

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South Africa is a country rich in flora—it is said to have more species per square mile than any other country in the world. The terrain is tremendously varied and includes deserts, subtropical grasslands populated with lions and elephants, subtropical forests and high mountains with peaks over 11,000 ft. in elevation. The climate varies from region to region as one moves across the country, resulting in a wide array of plants with different cultural requirements. Within the past decade, the number of cold-hardy plants from South Africa being grown in the western United States has increased dramatically.

The climate and landscape in several areas of South Africa have much in common with the western United States. South Africa is situated at the southern tip of the African continent between 25° and 35° south in latitude. Within its borders there are huge expanses of cold, middle elevation deserts and mountains—known as the Great Karoo and the Little Karoo—in the western and central areas of the country. These areas have predominately Mediterranean climates with winter rains and dry, hot summers; in the country’s highest mountains, the eastern Drakensberg Range, the rainy season reverses: cold, dry winters followed by wet summers. The geographic similarities between our climates contribute to the ability of many South African plants to thrive in our region.

The incredible number of South African plant species can be attributed to that region’s geologic history. South Africa, unlike the United States, has had a very stable geologic situation over many millions of years. While North America was at one time or another covered by ice caps, shaped and disrupted by volcanic activity and covered in part by inland seas, the settled situation in South Africa has allowed the plants there to slowly evolve and differentiate. The result can be found in more than 20,000 different plants, representing about ten percent of all plants on earth. The diversity of bulb and succulent species is particularly large.

English and Dutch colonists in the 17th Century first brought many of the fascinating plants of South Africa to attention and cultivation outside the continent. As a result (unbeknownst to many avid gardeners) quite a few of our most popular flowers and bulbs have a South African heritage. In gardens along the coast of California many of the lesser-known South African bulbs have been in cultivation for years. In the rest of the US, cold tender Gladiolus, Freesia, Clivia, Gerbera daisies, Phygelius, and annual Gazania are just a few from a diverse list of South African natives that we enjoy. Unfortunately for gardeners in the intermountain West, cold hardy South African perennials had not yet found champions in the gardening world, and were few in number and difficult to locate. Due in large part to the pioneering efforts of Panayoti Kelaidis, Curator of Plants at the Denver Botanic Gardens, this situation has changed.

Traditional horticultural wisdom had led us to believe that South Africa’s flora was predominantly cold tender. Luckily, with the early ‘90s introduction of two cold-hardy groundcovers, Delosperma cooperi and D. nubigenum to the Denver area, our thinking began to change. Mr. Kelaidis made his first South African plant expedition in 1994, successfully collecting great quantities of seeds and information. Upon his return he added his new collections to the ongoing evaluations at the Denver Botanic Gardens and distributed extra seeds to growers in the Denver area and myself for evaluation in our own gardens. His subsequent trips to other areas of South Africa resulted in the collection of more seeds to be grown and tested.

Other horticulturists in the western United States have offered seeds of South African plants throughout the years. By 1991 I had already been growing cold-hardy cacti and succulents from North America for 10 years before I stumbled across Mesa Garden, this country’s premier cactus and succulent seed supplier in Belen, New Mexico. Through the work of Steven Brack and Steve Hammer, seeds of hundreds of South African succulent species were being offered. By testing many of Mesa Garden’s collections in our USDA zone 5/6 Santa Fe gardens, we were able to begin making available cold-hardy succulents such as Ruschia pulvinaris, Aloinopsis spathulata, Nananthus transvaalensis, Rabia albipuncta and Titanopsis calcarea. Other cold hardy succulents that originated from Denver Botanic Garden collections include Delosperma congestum “Gold Nugget”, D. sphalmanthoides, Ruschia sp. aff. hamata, Ruschia sp. “Calvinia Pink” (formerly sold simply as Ruschia sp.) and Stomatium mustilinum.

Within the past five years several superb new cold-hardy herbaceous perennials have become more widely available. Some of these plants had been in cultivation for many years in England but hadn’t been tested for cold hardiness. Others are available as a result of Mr. Kelaidis’ collections through Denver Botanic Gardens. The most noteworthy D.B.G./Plant Select introduction would certainly be Diascia integerrima “Coral Canyon”. This superb everblooming cold hardy perennial has expanded the usefulness of the genus beyond its former use as annuals in container plantings and beds. Diascia integerrima “Pink Adobe”, introduced in 2002 by High Country Gardens, is a new dwarf form of the species with pale salmon-pink flowers.

Osteospermum daisies are another recent migration from annual plantings to the perennial border. Osteospermum barberae compactum “Purple Mountain” from the Mont-Aux-Source region of the Drakensberg range, and the awesome O. ecklonis “Lavender Mist” have both proven to be cold hardy and floriferous. Another easily grown and rewarding perennial is Gazania linearis “Colorado Gold” with its season-long display of bright yellow daisies. I had the good fortune to travel to the Drakensberg Range in South Africa this past year. With the guidance of Rachel and Rod Saunders, two of that country’s most knowledgeable native plant experts, our group enjoyed a highly productive tour of these spectacular mountains. The trip was very enlightening and gave me a much better understanding of the incredible diversity of South African plants and their growing requirements when cultured here in the United States. Certainly it has fanned the flames of my passion for this region’s flora, prompting me to redouble my efforts to continue testing and introducing more cold hardy species and their cultivars. Some plants I hope to make available in future years include wildflower bulb species like Gladiolus, Watsonia, and Dierma (Fairy’s Wand). New herbaceous wildflowers I hope will soon be thriving here include high altitude forms of Phygelius, Hirpicium, Diascia, Lobelia and Cotula.

These are exciting times in the horticultural world, spurred on by passionate interest in finding new and different perennials. The cold, high altitude regions of South Africa hold many treasures. As we continue our efforts to find and test these plants in the western United States, I think we’re in for many new and wonderful surprises

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