Purslane is an annual weed that germinates after soil warms in early summer. A native of Europe, purslane is related to the portulaca or moss rose grown in flower gardens. It has succulent leaves and a low-growing, mat-like growth habit. Clumps may grow to two feet in diameter.
Purslane is a problem weed in flower and vegetable gardens, where it competes with desirable plants for moisture. It's also frequently seen in newly-seeded lawns. Stems and leaves often have a reddish-purple tint, and the small yellow flowers open only on bright sunny days. Purslane thrives when it has plenty of moisture. It also can survive in dry spots, although it may be less vigorous and have smaller leaves.
Purslane produces high numbers of very small, black seeds that may remain viable in the soil for several years. The best way to control purslane is to keep it from producing seed. You can hoe it out of your garden, but it can redevelop from the taproot left in the soil. Plants pull out of moist soil easily, but it's important to bag and discard pulled plants, as those left on a moist soil surface can re-root. It's best to hoe or pull purslane as soon as it's identified and before flowering occurs.
Herbicides such as glyphosate, sold as Roundup, and 2,4-D sprayed on this weed can be effective, but seeds may mature in the time it takes for an herbicide to kill the plant. Purslane rarely develops in mulched areas, and mulch placed over purslane usually will smother it. There is a hornworm, similar to tomato hornworm, that feeds on purslane, but it rarely does significant damage.
Purslane does have a silver lining. Its leaves are edible and make a nice addition to salads.
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Updated Tuesday, July 22, 2014