chickweed, hen-bit, hen
Lamium amplexicaule L.
Henbit dead-nettle is a small native annual found throughout the UK on arable land and in waste places. It is recorded up to 1,500 ft in Britain and is almost always associated with the activities of man. Henbit dead-nettle is a weed of light and chalky ground. In an early survey of Bedfordshire and Hertfordshire, it was chiefly associated with light and sandy loams. It is a common weed of winter cereals but causes little loss of yield. In a study of weeds in conventional cereals in central southern England in 1982, henbit dead-nettle was found in 1% of winter wheat and 2% of winter barley and spring barley. Henbit dead-nettle seed was found in 2% of arable soils in a seedbank survey in Scotland in 1972-1978.
Henbit dead-nettle has caused mild neurological problems when eaten by grazing animals, but instances of this happening are rare.
Henbit dead-nettle flowers from April to August and then again in September-October. The flowers are visited by bees. It can produce flowers that do not open and self-pollination is then inevitable. The average number of seeds per plant is 1,000. The seed rain from plants emerging after a cultivation in April can extend from mid-June to the end of July.
Freshly shed seeds are dormant and after-ripen at different rates according to the ambient temperature. In controlled conditions, henbit dead-nettle seedlings emerged at temperatures of 5 to 25°C but emergence was greatest at 15 to 20°C. Emergence declines at low moisture levels. Seedling emergence from seed sown in the field and cultivated periodically through the year occurred in two main flushes, March to April and July to October, with the odd seedling emerging at other times.
In sandy loam soil, field seedlings emerged from the top 50-60 mm of soil with the majority from the upper 25-40 mm. There is some evidence that under plastic covers seedlings can emerge from down to 75 mm.
In field soil, seeds remain viable for 25 years. Seeds recovered from house demolitions and dated at 25 and 30 years old are reported to have germinated.
There is no obvious seed dispersal mechanism but an elaiosome attached to the base of the seeds is attractive to ants and this may aid dispersal.
Control is by surface cultivations in spring and autumn. Seedlings are largely destroyed by spring cultivations and constant use of the hoe. Henbit dead-nettle may increase under zero-tillage.
Residues of some harvested crops may promote the germination and early growth of henbit dead-nettle while others inhibit seedling emergence.
Henbit dead-nettle seed is susceptible to soil solarization.
Updated October 2007.