How to Plant Portulaca

A creeping plant 3 to 10 inches tall, which blooms whenever the sun shines during summer and early autumn, portulaca (Portulaca spp.) makes vividly-colored single or double 1- to 3-inch flowers similar to those of cacti blossoms. Its succulent foliage resembles 1-inch plump conifer needles for moss rose (Portulaca grandiflora) and 1 1/2-inch flat ovals for purslane (Portulaca oleracea). Although moss rose can be hardy in U.S. Department of Agriculture plant hardiness zones 10 through 11, and purslane in USDA zones 9 through 11, the plants usually are grown as warm-season annuals. When planting them, remember their preference for dry conditions.

The original moss roses only bloomed in the morning on sunny days, closing during the afternoon and remaining closed all day during cloudy weather. A few more modern cultivars, including "Afternoon Delight," "Sundance" and "Sunseeker," stay open for at least part of the afternoon as well.

The Pazzazz series of purslane reportedly also boasts flowers which close later in the afternoon than most. Its iridescent colors include, among others, "Red Flare," "Salmon Glow" and "Ultra Pink."

Portulacas require a position in full sun and actually prefer poor soil, which is dry, sandy and somewhat low in fertility, for the best bloom. They may grow more vigorously in richer ground, but won’t produce as many flowers there.

Select such a site after your area’s last spring frost, when temperatures have risen to between 68 and 86 degrees Fahrenheit. If the ground in your garden bed is heavy clay, dig 2 inches of compost into its upper 8 inches to lighten its texture, and till or rake the bed thoroughly to a fine consistency. Should you plan to grow portulaca in a container instead, choose a fast-draining soil such as cactus potting mix, also ensuring the container has drainage holes.

After moistening the soil, sprinkle portulaca's tiny seeds thinly over its surface, pressing them into that surface without covering them. If you keep their soil damp, the seeds should germinate within seven to 14 days.

Thin or transplant your seedlings -- or purchased ones -- so that they stand 5 to 8 inches apart.

While the seedlings are young, water them frequently enough that their soil remains lightly damp. Once well established, portulaca plants are drought tolerant and should require little irrigation.

Water those in the ground only when their soil is dry 1 inch down and those in containers when the top of their mix feels dry. Use a soaker hose or a watering can with a spout which can be inserted beneath the foliage, since water falling on the plants from above may cue the flowers to close.

If you must mulch the plants, choose a dry type of mulch such as fine gravel.