Drought-Tolerant Succulents Provide Striking Form and Color

  Mary IrishWith an emerging recognition of the limitations on water use, gardeners are turning to plants that come by drought tolerance naturally. Plants that grow in deserts and semi-arid regions have an innate fast track to drought tolerance while making a strong statement in a garden. And none of the wide array of desert-adapted plants make a grander statement in the garden than succulents.

Strictly speaking, a succulent is any species that has specialized tissues in its leaves, stems, or rarely in the roots or flowers that hold water. While succulents normally get water and its dissolved nutrients through their roots, in times of drought this stored water allows a metabolic shift away from the roots so that photosynthesis can continue uninterrupted.

Almost all succulents have hard surfaces, firm leaves and a striking form offering stunning contrast in the garden. The variety of color and form makes a good visual counterpoint to billowing, frothy perennials, grasses or small shrubs. In the Southeast in particular, this is a welcome relief from the unrelenting green and similarity of so many garden favorites.Agave ghiesbreghtii
Photos by Gary Irish

The most obvious advantages of using succulents generously are these plants are built for drought and do not need frequent or continuous watering. For most succulents, that is the surest way to kill them. Root systems of all succulents are shallow, fibrous and small for the size of the plant. This feature enables them to grow well in small or restricted spaces, such as containers.

A blended family
Blending succulents with perennials, grasses, bulbs and shrubs makes a rich garden. But keeping all the various types of plants healthy is not difficult, although a few tips may help.

• Provide excellent drainage. If the area is wet all the time, it is probably not a good spot for succulents. Keeping them continuously moist is lethal, even in a container.
• Water carefully. In a mixed bed watered with drip irrigation, succulents do best without a dedicated emitter. If possible, try not to regularly water succulents with overhead sprinklers or sprays.
• Know the light requirements. Not all succulents, even cactus, grow best in full sun. This is especially true in the low desert regions. Many succulents, like aloes, sansevierias and gasterias, are excellent choices for dry shade.Easter lily cactus (Echinopsis sp.)

Some solid choices
While there are dozens and dozens of wonderful succulents to select for a garden, below are a few that are some of the easiest to use in a mixed planting.

Many agaves blend well with low water use perennials and grasses. Among the most attractive are Agave parryi in all its forms, A. ghiesbreghtii with its white-lined leaves, A. desmettiana with its urn-shaped form, the unarmed A. bracteosa, and larger species like Octopus agave (A. vilmoriniana) and A. salmiana.

Yucca species from the eastern United States are particularly well suited to use in the garden. These include the familiar Yucca gloriosa var. recurvifolia and other forms of Y. gloriosa, Spanish dagger (Y. aloifolia) and Y. filamentosa. For drier areas, consider the grass-like plains yucca (Y. glauca) or Y. harrimaniae. The small pale blue-leaved Y. pallida and the green-leaved twisted yucca (Y. rupicola) are also easy to use in a mixed planting.

Aloes are especially effective in dry shade or in mixed succulent plantings. While there are hundreds of species from which to choose, the easy to find coral aloe (Aloe striata) is particularly lovely. The vining A. ciliaris or the upright A. vaombe also make outstanding garden plants.Prickly pear (Trichocereus sp.) blends well with drought-tolerant perennials.

There are so many species of cactus that it is hard to generalize their use within a garden. Most species of prickly pear blend well with drought-tolerant perennials and grasses. However, barrel cactus and most cholla species are best used with other highly drought tolerant species or in a mixed succulent bed. Both of these types do best in full sun in rocky, dry soils. Perhaps the easiest of all cactus to use in a garden are the summer flowering Trichocereus forms — either the white flowering species, T. candicans, or the numerous and vividly hued hybrids now on the market. These are good choices for light shade and intermittent watering and provide rounds of brilliant color over the summer.

Ice plant is a name that covers a broad category of plants that range from those with minute succulent leaves that vine along the ground to small shrubs. Members of the genera Drosanthemum, Lampranthus, Caprobrotus and Malephora are among the easiest to blend into a succulent garden. Almost all species are summer dormant, and in the low desert only want full sun in the winter. This combination makes them a splendid container plant where their conditions are hard to match.