Marshmallow (Malva parviflora
) is an upright or sprawling, summer or winter annual that is thought of as a common weed throughout North America. Marshmallow is native to the Mediterranean region but has been introduced worldwide as an ornamental. Marshmallow is identified by its distinctive, cheese-wheel like fruits and kidney-shaped leaves. Marshmallow appearance characteristics include:
- Young plants: It initially appear as a basal rosette.
- Root system: Straight taproot of varying lengths with a coarsely branched, secondary root system.
- Stems: 4 to 34 inches in length, branched stems which are covered in short hairs. The stems will often trail along the ground initially, until they turn upright at the end.
- Leaves: Green, wide, kidney-shaped and toothed edges with 5 to 9 shallow lobes. It has prominent veins that radiate from the center of each leaf, which are covered with short hairs on both sides. Leaves are alternative and attach to stems through long petioles.
- Flowers: 5-petaled flowers appear from May through October, and are white to pink to purple in color, notched at their tip, and can arise alone or in clusters from stem axils.
- Fruits: Fruits resemble cheese-like wheels, appearing as 10 to 20 rounded, flattened sections aggregated such that they form a ring. As fruits mature, they dry up and separate in segments, which each contain one reddish brown to black seed.
Marshmallow has been implicated as the cause of many cases of poisoning in livestock in Australia and a recently discovered cause of poisoning in horses in the United States. It has also been thought to be a potential cause of Australian stringhalt in horses.
- Rapid Breathing
- Muscle Tremors
- Profuse Sweating
- Increased Heart Rate
- Staggering Gait
- Muscle Weakness
MANUAL CONTROL: If found in small densities, pulling out young plants can be affective if taken out prior to the tap root becoming established. The taproot gets woody as it matures and is very difficult to cut or pull out.
MECHANICAL CONTROL: Shallow mechanical cultivation can be used while the plants are young. The cultivator should be set so that the blades or tines will pull the plants from the ground or cut the tap root below the soil level. Mowing is not an effective method of control because the plants have viable buds on the stems below the height of the mower blade. Common mallow tends to have a more prostrate growth habit so that species is even less affected by mowing.
CULTURAL CONTROL: Piling mulch on top of the plants can also be effective if it is at least 3 inches of organic mulch, such as bark or wood chips.
BIOLOGICAL CONTROL: The fungus, Colletotrichum gloeosporioides f. sp. malva, however it has had limited success.
CHEMICAL CONTROL: Products containing oryzalin, pendimethalin, or 2,4-D provide limited control when applied to young plants.