Euphorbia Decidua

Not a Bulb, a Stem

• Euphorbia decidua is a slow-growing, dwarf plant that's only about 8 or 10 inches tall at maturity, with curving, fleshy leaves that resemble branches more than leaves. The leaves can be 9 or 10 inches long on an older plant and arise from a fleshy stem, or caudex, that resembles a turnip and can be 4 inches in diameter. The caudex looks like a brownish bulb, but is actually a stem that would be below the soil line in the plant's native habitat. In pots, the plant's stem is usually planted about 50 percent above the soil and 50 percent below, to help prevent rotting when the soil is moist.

Leaves and Flowers

• A mature plant can produce tiny flowers, which are borne in small clusters at the ends of the fleshy leaves. Each flower is pale green, with a red center, but these occur only sporadically. The plant gets the name "decidua" from its habit of shedding its leaves each year, which would happen during the African dry season for a wild plant. When grown indoors, the plant usually loses its leaves in winter and takes on the appearance of a leafless turnip.

Soil and Light

• A typical succulent that stores water in its stem and leaves, this plant needs extremely well-drained soil to thrive. You can use a commercial mix labeled for cacti and succulents, or make your own from 2 parts standard potting soil, 1 part perlite or vermiculite, and 1 part small-sized gravel such as pumice or crushed granite, or substitute coarse builders-grade sand for the gravel. The final mix should not form a lump when wet, but stay crumbly. Like most succulents, Euphorbia decidua does best in bright light and thrives in a south- or west-facing window or in full sun outdoors. You can move a houseplant plant outdoors during the summer, but expose it to bright outdoor light gradually, adding an hour or two each day.

Water and Problems

• Euphorbia decidua is extremely sensitive to over-watering, which can cause its stem and roots to rot. If the plant's pot is in a saucer, remove the saucer before watering and let the pot drain fully before replacing it. Water the plant only when the top 1 to 2 inches of soil are dry, and don't water during the winter when the plant is leafless. Resume watering when you see the green tips of new leaves, which usually appear in late winter or early spring.