Sunday, August 21, 2011

Heart-shaped leaf that doesn't want to leave !

Ajay Nair
Department of Horticulture, Iowa State University

Heart-shaped objects not always bring fun and joy to our lives, certainly not this one. This weed, Abutilon Theophrasti, commonly referred to as velvetleaf, buttonweed, wild cotton, or Indian mallow has been slowly invading soils under vegetable production. Flower and seeds are produced from July through October and the seeds can remain viable in the soil for about 20-40 years. The plant is 3-7 feet tall and has  large heart-shaped leaves usually 2 to 5 inches wide. Velvetleaf causes the most concern in row crops, however, it can create problems in vegetable production as well. The plant can compete with vegetable crops for water, nutrients and due to its erect growth habit can also shade plants in its vicinity.

It has been reported that leaves and seeds of this plant carry allelopathic chemicals that inhibit the germination and growth of crops, such as radish and turnip.  A number of pre- and post-emergent herbicides are available to control velvetleaf, but more importantly, steps should be taken to reduce its seed bank in the soil. Crop rotation, avoiding excess N application, and hand pulling small populations (remove from the field or burn, since the seeds will ripen after the plant is pulled) will help to control velvetleaf. Velvetleaf becomes less of a problem in no-till systems because if seed germinates on the soil surface, it dies. Some amount of biological control also occurs (velvetleaf seed beetle destroys developing seed; fallen seeds are eaten up by mice and ground beetles) but the best practice is not to let the plant go to seed and, if it does, then removal and destruction of the plant is the next alternative.

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