- Waterwise Gardening | David Salman
A Year-Round Plant Paradise
Evergreen Succulents for the Cold Weather Xeric Garden
Travel to the Pacific coast of California and you'll encounter a wonderland of succulent-rich landscapes. Combinations of beautiful specimen succulents around building entrances and front yards combined with expansive flat and sloped areas blanketed with succulent groundcovers, make for a year-round plant paradise in these very mild (USDA zone 9-10) winter climates.
While gardeners in cold winter regions like the Intermountain West may not be able to use these same plants, we have available our own unique mix of winter hardy succulents to create a similar look. Hailing from cold winter regions of the Southwestern and Intermountain U.S. as well as the Chihuahuan desert in northern Mexico, there are a surprising number of native succulents that grow well in USDA zone 5-8 climates. By combining these native succulents with the large number of cold hardy South African and Old World species now in cultivation, western xeriscapes (waterwise landscapes) can also display endless combinations of these evergreen plants to "green-up" our winters and dazzle us with summer flowers.
Using winter hardy succulents will reward the gardener with many benefits:
Succulents are indispensable plants for fire-safe landscapes, as their foliage is full of water. Large areas of succulent groundcovers around homes and outbuildings are much preferred over gravel, being more colorful, have a cooling effect on the property and are habitat-friendly for pollinators.
Succulents are also very waterwise, and require much less supplemental irrigation than traditional landscape plants and lawns.
Many of these plants are very long lived and can grow to impressive size.
And lastly, they bring much needed winter interest to predominately brown, dormant yards attracting our eye with the striking color and geometry of their stems and leaves.
Design Ideas and Companion Evergreen Plants
Large growing Yucca, Agave and Dasylirion make spectacular specimens, and should be planted in prominent positions, but not along the edges of sidewalks and gates where their spines can grab or stab pedestrians. Push them back into the yard so you can marvel at their dramatic presence as they get quite large with maturity. They can be grouped into dramatic arrangements placing the tree yucca species in the back and surrounding them with mid-sized growing Agave, Hesperaloe and Nolina.
Delosperma cultivars, Ruschia pulvinaris and groundcover Sedum are excellent lawn grass substitutes and will happily carpet small and large expanses. They are especially useful for covering slopes . I recommend mixing various Delosperma varieties to create a spectacular tapestry of different colored flowers.
To enhance the year-round interest provided by succulents, evergreen shrubs make excellent companion plants. Native shrubs and such as Mountain Mahogany (Cercocarpus), Cold Hardy Manzanita (Arcostaphylos), Mahonia (Mahonia), Great Basin Sage (Salvia dorrii) and Mojave Sage (Salvia pachyphylla) and dwarf selections of pines like Pinon (P. edulis and P. monophylla), Ponderosa (P. ponderosa) and Scotch (P. sylvestris) are quite xeric and fit nicely alongside their succulent neighbors. Old World evergreen shrubs like Lavender (Lavendula) and Rosemary (Rosmarinus) and Cold Hardy Curry Bush (Helichrysum tianshanicum) provide contrast and their aromatic foliage is a delight after a summer rain.
Of course non-evergreen native and Old World perennials, flowering bulbs and ornamental grasses are also excellent choices to fill in a young xeriscape as the succulents grow to larger size. In addition, they provide more flowers and nectar for pollinators.
The use of these cold hardy succulents as the focus of low maintenance cold area xeriscapes is a relatively new concept.
And it gives gardeners many creative possibilities when designing plantings that incorporate them. I strongly recommend that these plants be installed in the spring so they have a full growing season to establish themselves before the winter cold. Listed below are some of the most versatile and readily available cold hardy succulents.
Native Cold Hardy Evergreen Succulents
Here is a list of some of the best and most cold hardy succulents for Intermountain and Southwestern xeriscapes (USDA zones 5-9).
Century Plant (Agave) - A huge genus, many cold hardy species have been put into cultivation over the last decade or so. These cold hardy plants come from west Texas, New Mexico, Arizona and Nevada. They range in size from the miniature Agave toumeyana v. 'Bella' (z. 5-10) to large specimens of Agave havardiana (z. 6-10) , native to west TX, that have 3 to 4 ft. wide rosettes. Other species include Agave parryi, Agave neomexicana, Agave utahensis and A. utahensis subspecies.
Yucca (Yucca) - these are some of the most cold hardy with many species thriving in regions with winter temperatures of -20° F or lower.
Yucca baccata, Yucca glauca, Yucca angustissima, Yucca harrimaniea are the most cold hardy in zones 4-9. For zones 6 and warmer, Yucca rostrata, Yucca elata, Yucca faxoniana are all tall stemmed desert "trees" that can get huge and make stunning specimens in the dry garden.
Sotal or Desert Spoon (Dasylirion) - Dasylirion texana is zone 5 cold hardy with long green leaves. Dasylirion wheeleri has gorgeous blue or blue-green leaves but is slightly less cold hardy (zone 6).
Beargrass (Nolina) - There are two very cold hardy species that look like large evergreen grasses in the xeriscape, Nolina greenii and N. microcarpa. The flowers, held on stiff spikes, are essential nectar sources for native bees.
Spineless Pad Cacti (Opuntia) - Opuntia elisiana and O. engelmannii 'Inermis' are two stunning additions to the xeric garden providing big yellow flowers in late spring and architecturally interesting spines pads.
Ocotillo (Fouquieria splendens) - with long thorny branches and amazing displays of rain-triggered scarlet flowers in spring and summer, this species is a magnet for hummingbirds and other desert pollinators. Plants from the Chihuahuan desert of south-central NM are by far, the most cold hardy selection of the plant, tolerating winter lows in zone 6. Place in front of hot west and south facing walls and corners; ocotillo loves heat.
Stonecrop (Sedum) - Low growing groundcover types are evergreen and have stems that root as they spread across the ground. Showy summer flowers are either pink or yellow and are excellent for providing nectar to bees.
Texas Red Yucca (Hesperaloe) - A great non-spiny succulent forming clumps of long strap-like leaves. In spring, arching stems of bear hundreds of hummingbird-attracting flowers. Ever blooming selections like 'Coral Glow', Brakelights® and 'Straight Up Red' are nearly seedless and provide flowers from late spring to early fall.
South African Cold Hardy Evergreen Succulents
Shrubby Iceplant (Ruschia) Ruschia pulvinaris is the best of the genus, being very cold hardy and rabbit-resistant. It blooms with a carpet of incredibly bright magenta flowers in mid-spring.
Groundcover Iceplant (Delosperma) - There are many excellent cultivars (selections) that provide fabulous flowers and abundant nectar for bees. Delosperma ashtonii 'Blut', D. cooperi and D. hybrid Red Mountain® Flame are three of my favorites.
Pig's Ear (Cotyledon orbiculatus) - Collections made from the high elevations of the Drakensberg Mountains of South Africa provide us with cold hardy plants. Stunning silver, red-edged leaves form the rosette from which emerge a sturdy stem with a crown of pendulous orange tubular flowers in early to mid-summer.
Lion's Spore (Euphorbia clavariodes) - Again, high elevation collections from the Drakensberg Mts. are cold hardiest. They grow to form large mounds of small rounded stems. Numerous tiny yellow flowers cover the stems in early summer. This species is completely resistant to browsing rabbits too.
Dwarf Mesembs (Aloinopsis, Nananthus, Stomatium, Rabiea and other genera) - These are small growing plants with incredibly colorful flowers held on top of equally fascinating leaves. Use these in the rock garden or as container plants (the pots can be left outside all year-round).
Old World Cold Hardy Succulents
Stonecrop (Sedum) - Groundcover types are found both in North America and Europe.
Hens and Chicks (Sempervivum) - Beloved Hens and Chicks have clustering rosettes of foliage and spread to form mounding clumps of showy foliage. There are literally hundreds of selections to choose from. Place them around larger succulents or tuck them into rocks.