A sprawling annual plant with long, trailing, easily-broken stems, and many soft, pale green leaves
Flowers are in loose clusters each flower about 1 cm across with five, fine, white and very deeply divided petals
Leaves are light green, hairless (but with short hairs on the margins towards the stalk), oval shaped with a pointed tip and in opposite pairs on hairy stalks
Fine hairs run along one side of the stems/branches that rotate position by 90° at each node
To distinguish chickweed from other plants, the stem may be pulled so that it breaks around the outside. The centre of the stem will stretch if it is chickweed.
Biology
Origin and habitat
Native to Europe
Spread throughout the world by humans as the plant has been widely used as a vegetable and as a herbal remedy
Chickweed is very common throughout New Zealand, growing quickly in arable crops, pastures, gardens, lawns and waste places
Bare ground and pastures damaged by winter pugging are very vulnerable to chickweed invasion
Chickweed can grow in denser shade and at lower temperatures than many other weeds
Chickweed can grow over the winter months but does not survive dry conditions and dies back in most summers
Its prevalence increases as soils become more fertile.
Life cycle
Chickweed usually germinates in autumn or winter and grows through winter and early spring
Chickweed is an annual, producing flowers and seed very quickly
Small seeds are easily dispersed in mud or dirt. Up to 2500 can be produced per plant, which means millions of seeds are often buried in the soil
Some seeds germinate within a few months of dispersal provided conditions are favourable, but others can last in the soil for years. It takes 3 years for the seed bank to be reduced by 50% and about 18 years to deplete the seedbank by 99%
When conditions are right i.e. damp, disturbed soil or bare patches, the stems of chickweed can root at the nodes.
Benefits
Both plants and seeds are readily eaten by birds, make useful fodder for lambs, and are said to increase the output of hens’ eggs
Leaves and young shoots are used in green salads and boiled as a potherb in several countries from India to North America, although the flavour becomes bitter with age.
Impacts
Chickweed can be persistent in high producing pastures, especially in cool or shady conditions
This weed can shade and smother young crop seedlings because its mat-like growth makes it a strong competitor.
Control
Grazing management
Although livestock do not readily eat chickweed, it may be controlled by trampling during grazing
Pugging in winter should be avoided where possible.
Other methods
Improved drainage may help reduce chickweed
Harrowing breaks the tender stems and reduces its competitive growth.
Chemical control
Chickweed is fairly tolerant to foliar applications of MCPB, 2,4-DB, 2,4-D and MCPA
Dicamba controls chickweed but also damages clovers
Several herbicides used in field/horticultural crops control chickweed effectively.
Further information
Popay I, Champion P, James T 2010. An illustrated guide to common weeds of New Zealand. New Zealand Plant Protection Society, Christchurch, New Zealand. 416 p.
Young S 2013. New Zealand Novachem agrichemical manual. Agrimedia Ltd, Christchurch, New Zealand. 767 p.
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