Horticulture Principles and Practices

frost-hardy. Their rosettes are usually bigger than those of the Sempervivum genus.
Also, they exhibit a wider variety of leaf shapes and colors, many of the leaves being
edged in a contrasting color (Figure 14–8). Most of the species have a powdery of waxy
surface. Their flowers are bell shaped. Some of the common species are E. lilacina and
E. shaviana.
Yucca
Succulents in the Yucca genus are not as widely used in the landscape as the other families
previously discussed in this section. Many species are sharply spined. There are variegated
species that create interest in the landscape. A popular species, Y. elephantipes,
is used as a houseplant. Another species of interest is the Y. filamentosa.
Euphorbia
This is the largest genus of succulents. Commonly referred to as spurges, species in the
genus Euphorbia are characterized by plants with tiny flowers that lack petals. Instead, the
showy parts of the plant are its brightly colored bracts. Another noteworthy distinction is
milky sap or latex that exudes from the plant when cut or snapped. This milky sap is an irritant
to the mucous membrane. When grown in the house, they should be kept out of reach
of children and pets. The most popular species in this genus are the E. pulcherima (Poinsettia)
(Figure 14–9) and E. milli (crown of thorns). This genus contains species with
widely differing features. E. horrida and E. echinus are leafless with swollen spiny stems
that resemble a cactus. The Mediterranean spurge, E. characias, has erect woody stems that
can reach more than three feet tall.
Sedum
Commonly called the stonecrops, Sedum species are found mainly on rocky, mountainous
regions (Figure 14–10). They belong to the family Crassulaceae. They may be
divided into three general categories according to how they are used in the landscape. The
group of upright and showy species, exemplified by Sedum spectabile (showy sedum),
can grow to heights of about 2–3 feet and add color to gardens and borders. The group of
trailing sedums is effective as edging plants for flower beds. The third group of sedums
FIGURE 14–8 Hens and chickens
(Echeveria sp) (Source: Dorling Kindersley)
FIGURE 14–9 Poinsettia (Euphorbia pulcherima)
(Source: Matthew Ward © Dorling Kindersley)
14.3 Popular Succulents (Noncacti) 455