Common mallow (Malva neglecta), a low-growing herbaceous annual, has heart-shaped leaves,and pale pink, white or lavender flowers. The plant is generally considered a weed due to its tendency to self-sow freely in lawns and gardens. Though edible and vitamin-rich, common mallow can be toxic when grown in high-nitrogen soils. If you have any concerns about mallow poisoning, call the free American Association of Poison Control Centers Poison Help Line at 1-800-222-1222.
If grown in soils that have been enriched heavily with nitrogen fertilizer, common mallow will have an excess of nitrates. The nitrates are generally concentrated in the stems, and are strongest in the mornings and evenings when the plant's metabolism is most active, notes Utah State University. Most people have internal mechanisms that will remove nitrate from the body without causing harm, according to Delaware Health and Social Services. Symptoms of nitrate poisoning in humans include bluish tinged skin, while pets may experience drowsiness, shakiness and difficulty standing.
Common mallow leaves are described as "perfectly wholesome" in most growing conditions by Plants for a Future. The leaves and young shoots are edible raw or cooked, and may be used as a lettuce substitute in salads or as a soup thickener. Tea can be made from the dried leaves, and the liquid derived from the boiled taproots can be used in place of egg whites to make meringue. Utah State University Cooperative Extension describes the leaves as being rich in vitamins and minerals.
Common mallow is tolerant of a wide range of growing conditions, adding to its effectiveness as a weed. It prefers well-draining soil and bright, sunny conditions. It is not at all picky about soil pH or watering conditions. Little mallow (Malva parviflora) is nearly identical to common mallow, though its petals are slightly longer and its fruits are wrinkled rather than smooth. As with common mallow, little mallow produces edible leaves that can harbor high levels of nitrates in the leaves when grown in inorganically rich soils.
If you do not want common mallow in your garden, the University of California Statewide Integrated Pest Management Program recommends digging up the plant with a hoe or by hand when the plant is young. Older plants have a long, woody taproot that makes removal more difficult. As a preventive measure, cover the soil with a 3-inch layer of organic mulch, such as bark or wood chips, to help suppress germination. Mowing is not considered an effective management strategy.
- Oregon State University, Small Farms: Poisonous Plants Commonly Found in Pastures
- Oregon State University Extension Service: Nitrate and Oxalate Poisoning
- Plants for a Future: Malva Neglecta
- University of California Statewide Integrated Pest Management Program: Mallows Management Guidelines
- Utah State University Cooperative Extension: Common Mallow
- Plants for a Future: Malva Parviflora
- Delaware Health and Social Services: Frequently Asked Questions: Nitrate and Nitrite
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