American Nurseryman Magazine - Horticulture Magazine and Horticulture Books - A Succulent for All Seasons - July, 2012 - FEATURES

American Nurseryman Magazine - Horticulture Magazine and Horticulture Books - July, 2012

FEATURES

A Succulent for All Seasons

From the Southwest to the Southeast and points in between, succulent plants have proved they're not just for desert gardens. These dryland plants add color and unique shape to mesic landscapes as well.
By Kathy Fitzgerald

Definitions

  • Dryland garden: a plot that receives little or no supplemental water after establishment.
  • Mesic: moderately moist habitat, with 25 to 50 inches of annual rainfall.
  • Rock garden: a raised area of coarse, low-fertility soil dedicated to small, low-growing perennials of alpine, saxatile or xeric origins.
  • Saxatile: living on or among rocks.
  • Xeric: dry or desert-like habitat, receiving 15 inches or less of rainfall per year.
  • Xeriscape: an attractive grouping of plants with low water requirements.

The word "succulent" conjures up images of cacti-studded expanses, adobe buildings and Georgia O'Keeffe paintings of chalky cow skulls. As more frequent and more severe droughts become the nationwide norm, however, it's time to reexamine old prejudices about the suitability of this remarkable group of plants in less arid environments. While spare, ocher-toned Xeriscapes of the American Southwest look out of place among the beaches, pine barrens and mixed forests of my home in eastern North Carolina, succulents have a place in mesic environments.

Culture club

Simply stated, a succulent is any plant that stores water in its tissues, but not all of them originated in deserts. Some hail from chilly, fog-shrouded mountains in China and Japan. Some - prickly pear cactus (Opuntia humifusa), many yucca species - are native to the southeastern United States. Where nighttime temperatures stay above 85° for extended periods, some even appreciate regular watering and shade.

The palette of succulents hardy to Zone 8 and north is extensive. They come in many forms and textures: soft, trailing sedums, portulacas and ice plants; formidable spears and spikes of yuccas, sotols and agaves; intricate ground-covering mats of hens-and-chicks; and armed-and-dangerous pads of prickly pear. Foliage and flowers span the spectrum from reds and yellows through blues and lavenders to silver-grays, whites and every shade of green. They are easy to grow, easy to propagate, undemanding in the maintenance department, and combine beautifully with other dryland perennials. Most thrive in poor soils, low-water conditions and dry shade.


Arizona? No, North Carolina. Agave americana, Opuntia humifusa (prickly pear cactus) and sotol (Dasylirion texanum) form a forbidding barrier between Wilmington's Zone 8 Gardens' parking lot and the adjacent strip mall. Top corner, Subtly variegated Agave lophantha 'Splendida' is the embodiment of Fibonaccian perfection. (Fibonacci? Fibonacci sequence? Fascinating subject; you should look it up. But finish this article first.)
Photos scourtesy of Kathy Fitzgerald

The trait of being satisfied with what moisture falls (or not) from the sky makes succulents an attractive adjunct to more traditional ornamental gardens that rely on supplemental water to look their best. They also boast fire-retardant properties: High moisture content, a preference for dry, sunny locations and low water needs make them perfect perimeter plants for wildfire-prone properties. Lightweight, fleshy-leaved genera like Sedum, Delosperma, Sempervivum and Portulaca have already established themselves as the darlings of green-roof and green-wall designs. Most prefer neutral to slightly acid, non-compacted soils, but can adapt to whatever you've got.

In humid climates, succulents require sharp drainage and good air circulation to prevent their fleshy or fibrous leaves and stems from becoming prey to fungal blights and rots. Planting on slopes, at the top of berms, or in raised beds or rock gardens and coarse, non-organic mulches - like gravel and decomposed granite - helps keep fungi at bay. Snugging succulents up close to or in crevices of heat-holding rocks can stretch the hardiness envelope for some tender genera.

Another way to introduce succulents to mesic and hydric environments is to plant them in containers. In addition to drainage control and precision-watering opportunities, containers raise plants closer to eye level, the better to appreciate their intricacies, and reduce jarring juxtapositions by providing isolation. The final plus of pots is that they can be moved inside to protect tender specimens when cold weather arrives.

Few plants propagate easier than succulents. Cuttings produce roots even if you don't get around to putting them in soil. In Designing with Succulents, Debra Baldwin notes that "[s]ucculents are able to reverse the flow of growth, sending nutrients from stems and leaves into root formation." If a cutting's leaves shrivel, she tells us, they'll plump back up as new roots establish. Plants can also be created by root division. Many genera produce offsets, bulbils or plantlets that can be separated from the parent plant to begin independent lives. As to timing, increase most hardy succulents in spring as they swing back into active growth.


Surely you remember Portulaca from your mother's-or grandmother's-garden. This long-trusted plant is back in vogue.

Getting in on the ground level

Portulacas, sedums, ice plants and hens-and-chicks represent the softer, kinder side of succulents. Lately it seems dozens of new selections of these low-growers roll out every spring. All are breeders' dreams: Sedums alone include over 300 species, and there are more than 2,500 types of ice plant to play with. Super-hardy groundcover and container denizen hens-and-chicks (Sempervivum spp.) are also enjoying a resurgence in popularity.


Assorted Sempervivum show off the variation in color and form that make hens-and-chicks a succulent favorite.
Portulaca (P. grandiflora, also called rose moss) and its weedy cousin purslane (P. oleracea) have long been stalwarts of dry gardens. They have the distinction of being among the few true annuals of the succulent world, known for the long period of jewel-toned flowers.

The epitome of easy-care plants, sedums don't mind hot, dry, nutrient-poor soil, but will do even better with occasional moisture. Some species even hanker for partial shade. All are shallow-rooted, eager spreaders. Readily available evergreen species include: S. rupestre 'Angelina,' a chartreuse-foliaged trailer that takes on a ruddy hue in cold weather; the variegated 'Tricolor' and dark red 'Dragon's Blood' cultivars of S. spurium; cool blue S. reflexum 'Blue Spruce'; tiny-leaved golden S. mackinoi 'Ogon'; and Oregon native S. spathulifolium 'Cape Blanco'. Use several to create a crazy-quilt buffer zone around the spikier plants mentioned below.

Hailing from South Africa's Drakensberg Mountains, ice plants - so-called because some species' foliage appears coated with ice crystals - comprise several genera, including Delosperma, Drosanthemum and Dorotheanthus. Give the crowns sharp drainage (they thrive planted in crevices between rocks and on slopes) and an inch of gravel mulch. Cultivars of Delosperma cooperi are most common in the trade, but Drosanthemum floribundum selections and the tender Dorotheanthus bellidiformis 'Mezoo Trailing Red' may soon take up a larger share of table space in garden centers. Although usually evergreen, ice plants can die back to the ground in particularly cold or wet winters.

The most cold-hardy succulent (to Zone 3), hens-and-chicks runs a gamut of color, texture, form and size. Rosettes range from a mere half-inch to 8 inches across, with smooth or pubescent leaves whorled tightly or loosely, and spider-web-like filaments present or absent. With more than 4,000 named cultivars to choose from, you may find yourself a collector before you realize it. (Don't ask me how I know.) Sempervivum are monocarpic, from the Latin for "one harvest." Rosettes die after producing blooms. Not to worry - the hen will have produced tons of chicks.

Raising your sights

Nothing screams "focal point" as loudly as a well-placed agave, yucca or sotol. These substantial, touch-me-not beauties command attention in the landscape, serving both as specimens and as anchors in dryland borders.


Prickly pear and agave make a dramatic focal point and require little supplemental water-a bonus even in non-arid climates.

The hardy agaves (Zones 5 or 6 to 10) all call North America home. The shapes of their chunky, three-dimensional leaves differentiate one species from another, although the leaf margins of all are spined. From the familiar powder-blue Agave americana and its cream-yellow-and-pink variegated cultivar 'Marginata', to the elegantly subtle midrib stripe of A. lophantha; from the dainty wispiness of A. geminiflora to the ferocity of the hybrid A. 'Jaws'; to the stately A. victoriae-reginae, there's an agave out there for every gardener. Referring to frequency of flowering, the common name "century plant" is a misnomer - agaves send up their impressive flower spikes after 15 to 30 years, not 100. Like Sempervivum, agaves are monocarps. The mother plant dies after blooming, but not before replacing itself with multiple offsets, called "pups."

The yucca family is large, its taxonomy muddled and confusing. Golden- and variegated-leaved cultivars often labeled as Yucca filamentosa (Adam's needle) - 'Bright Edge', 'Golden Sword', 'Variegata' and 'Color Guard' - may actually be cultivars of Y. flaccida (weakleaved yucca).

Then we have common names adding to the confusion: Y. aloifolia is called Spanish bayonet or dagger plant, while Y. gloriosa (or perhaps it's Y. faxoniana) goes by Spanish dagger. There are beaked yuccas (the beautiful blue-foliaged Y. rostrata), spineless yuccas (Y. elephantipes) and the Great Plains' own weedy soapweed (Y. glauca). And don't forget the false or red Texas yucca, Hesperaloe parviflora, which pretty much looks like a yucca until it blooms, when the flowers open coral-red or yellow instead of white or ivory. They all have tough, fibrous leaves, highly resistant to evapotranspiration.

Less well-known are the sotols, Dasylirion texanum. Also known as desert candle because of the shape of its bloom spike, sotol's saw-edged foliage forms large spheres when mature. From a prudent distance, it looks like one of those fiber-optic-cable sculptures. As easy-care as any of its relatives, Dasylirion provides a solid but breeze-mobilized anchor to a dryland garden.

The wickedly barbed-spined prickly pear (Opuntia humifusa) makes quite a statement as well, especially when in bloom. Controversial as a garden-worthy plant, prickly pear's somewhat lumpen habit is an acquired taste. Still, the plant offers all-season interest: A well-sited clump could replace a lack-luster shrub, as long as you don't ask me to get anywhere near it.

To forestall potential lawsuits, take pains to place all these plants well away from walkways and places where children and pets play.

Mixing it up

Succulents blend beautifully with other dryland plants in mesic gardens, filling either starring or supporting roles. Try planting them with ornamental grasses, like blue fescue (Festuca glauca), ponytail grass (Stipa tenuissima), fountain grasses (Pennisetum spp.) or muhly grass (Muhlenbergia capillaris). Flowering companions include blanket flowers (Gaillardia aristata), butterfly weed (Asclepias spp.), hummingbird mints (Agastache spp.), euphorbias (such as E. × martini hybrids or the otherworldly E. tenuifolia), lantanas, penstemons and salvias. Succulents also work well with herbs, especially lavender, thyme, prostrate and upright rosemary, culinary sage and fennel. An eye-catching border can be fashioned by pairing blue or red-foliaged succulents with silvery Artemisia 'Powis Castle', lambs-ears (Stachys by-zantina) or stalwart dusty miller (Senecio cineraria).


A brave little Agave americana 'Marginata' pup peeks out from beneath its mother's protective blades.

The last word

These fascinating and versatile plants deserve to be on the must-have list for every grower, garden center and gardener. Fleshy-leaved or fibrous, ground-hugging or statuesque, succulents add dramatic year-round texture and substance to ornamental landscapes. Conservation of water, low maintenance profiles, and ease of propagation are more compelling reasons why incorporating succulents into mesic gardens is an idea whose time has come.

Kathy Fitzgerald is a landscape designer and contractor and, with her husband Tim, is co-owner of Fitzgerald's Gardening in Oak Island, N.C. Out in her Zone 8 garden, her hens-and-chicks collection keeps pace with her Aeonium envy. She natters on about both, and many other things, in her blog, Gardening from the Ground Up, at www.gardeningfromthegroundup.blogspot.com. She can be reached at ksftsf@gmail.com.