Succulents sizzle in Southern California gardens

Columns - Regional Plant Specialist

Fleshy-leaved plants add color, practicality and whimsy to dry-climate landscapes.

March 24, 2010
Debra Lee Baldwin

Plants of the Elfin Forest Firesafe Demonstration Garden in spring (by flower color): Calandrinia grandiflora (purple); Bulbine frutescens (yellow), yellow-orange California poppies, and coral aloes. In the midground, not in bloom, are gray and green varieties of Cotyledon orbiculata and red-leaved Kalanchoe luciae.

Graptoveria ‘Fred Ives’ offers varying foliage colors at different times of the year.

In the sea-themed succulentscape at the San Diego Botanic Garden, aloes, crassulas, portulacaria, and crested cacti grow amid lava rocks stacked to resemble a reef. An alluaudia limb that bisects the composition enhances the illusion; it appears to sway in an ocean current. Design by Jeff Moore and Bill Teague.

Euphorbia tirucalli ‘Sticks on Fire’ serves as a backdrop to Agave americana ‘Mediopicta Alba’ (tuxedo agave) underplanted with blue Senecio mandraliscae. Carolyn and Herb Schaer garden, San Diego. Design by Michael Buckner, the Plant Man Nursery, San Diego.

In frost-free areas of the drought-ridden Southwest, succulents with colorful leaves and intriguing textures are the celebrities of the plant world and the darlings of landscape designers.
These geometric, architectural plants are defined by their ability to store water in fleshy leaves and stems. But I think the most appealing aspect of succulents is their foliage, which comes in bronze, blue, silver, gray, crimson, yellow, chartreuse, lavender and variegated. Many succulents also are highly textural. Blooms are long-lasting — both on the plants and as cut flowers — and blaze in colors even brighter than the leaves.
In midwinter in frost-free regions, aloes send up candelabra-shaped spires — often several feet tall — massed with tubular orange blossoms. And in garden centers everywhere, flowers of common Kalanchoe blossfeldiana hybrids, sold as tabletop plants, are as bright as a box of crayons.

Color comes at a premium
Colorful succulents tend to be more costly and harder to come by than their solid green cousins. Retail nurseries have difficulty keeping them in stock — especially variegated varieties that are challenging to tissue-culture. But growers are on top of the situation, and supply is catching up. It helps that stem succulents propagate readily from cuttings, and many rosette succulents produce offsets.
Cultivation often makes a difference when it comes to color intensity. Pork and beans (Sedum × rubrotinctum), Euphorbia tirucalli ‘Sticks on Fire’ and many crassulas, echeverias and aloes change from green to red, orange or yellow only when grown in full sun or when stressed by cold or drought. Others, such as the blue senecios, retain their hue, regardless. Graptoveria ‘Fred Ives’ is a chameleon; its foliage combines peach, rose, blue-green, and lavender-gray in varying intensities at different times of the year. 
Succulents with gray, gray-blue, or blue leaves can create a surreal combination seldom seen in cultivated gardens. It also is effective to contrast such plants with succulents that have darker or reddish leaves, such as magenta-black Aeonium arboreum ‘Zwartkop’ or orange-red Kalanchoe luciae, and with low-water perennials that bloom in crimson, gold, or yellow-orange.

Design possibilities abound
Because of their compact and unusual shapes, striking foliage, and ease of maintenance, succulents lend themselves to imaginative, nontraditional gardens. The plants can be used as wildfire barriers, for green roofs, in rock and boulder landscapes, with cacti, and in seaside gardens that tolerate salt spray.
Fire prevention experts in Southern California advise homeowners to plant succulents because the leaves have a high moisture content and do not contain flammable oils or other volatile chemicals. Many varieties grow close to the ground, but even the largest will not provide a fire ladder that enables flames to reach the eaves of a house. Moreover, succulents stay lush and healthy with minimal irrigation, so they are well suited to perimeter areas that receive less water than those closer to the structure.
Designers are using succulents that resemble undersea flora to create whimsical garden vignettes. The key to getting the right look for an undersea-themed succulentscape is to create canyons, because an undersea reef is not flat. Start with as many lava rocks as you can find, because most coral reefs are volcanic. (Lava rock resembles a sponge and is lightweight; it is full of holes formed when the rock was molten and foamy.) Build vertically or on a slope, so when you look at the seascape, you get a sense that you are in the midst of it. Accumulate multiples of plants, because a seascape looks more natural with clusters and repetitions.
Once the stacked rocks suggest a reef, fill crevices with potting soil, and tuck plants (or callused cuttings) into them. Mulch with fine pea gravel in the same color as the rocks, and cover the canyon floor with white sand. You also might add props — such as a rusty anchor and chain or half-buried urns that resemble amphorae (perhaps planted with an aporocactus that suggests a moray eel). 
Globular cacti such as golden barrels (Echinocactus grusonii) add spherical shapes, buttery color and prickly textures to gardens, and are effective planted in multiples. When arranged in rows to create geometric arrangements, globular cacti have a Zen-like simplicity.
Peter Bailey of Escondido, Calif., created a checkerboard of golden barrel cacti in an area of his back yard most often viewed from upstairs windows. He first installed drip irrigation lines, so the cacti could be watered during the dry summer and autumn months. Next, to prevent the encroachment of weeds, he lined the 700-square-foot area with black plastic. After positioning 25 concrete pavers 2 feet apart to create a grid, he cut into the plastic and planted the cactus in the intersections, and then paved exposed areas with crushed rock. To tie the garden to the larger succulent garden beyond, he replaced one of the squares with an aloe tree (Aloe bainesii).

Easy-care containers
Cultivating succulents in containers meets the needs of space-constrained homeowners who want visually engaging, waterwise and low-maintenance plants. Pots of easy-care succulents can be grouped on patios, balconies, decks, entryways, and sitting areas — any place that receives adequate warmth and sunlight. And because containers can be moved indoors or beneath a shelter, they make it possible to grow succulents in climates too cold or wet for in-ground cultivation.
Unlike potted annuals, which need to be replaced seasonally, and perennials that require repotting after a year or two, most succulents will last three or more years in containers. Some of the most dramatic potted displays are single specimens with crisply defined shapes, such as Agave victoria-reginae. Also pleasing are succulents that suggest fleshy flowers, such as aeoniums, echeverias and sempervivums.
As in the landscape, when you combine more than one type of succulent in a container arrangement, or include companion plants with similar requirements, the design possibilities are limitless. 

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