Agriculture Reference
In-Depth Information
(a)
(b)
Figure 17.8
(a) Chickweed plant; (b) seedling
17
ha) are most commonly found in the top 7 cm of
the soil where, under conditions of light, fluctuating
temperatures and nitrate ions, they may overcome
the dormancy mechanism and germinate to form the
seedling. Many seeds, however, survive up to the
second, third and occasionally fourth years. Figure
17.11 shows that germination can occur at any time
of the year, with April and September as peak periods.
Chickweed is an alternate host for many aphid-
transmitted viruses (e.g. cucumber mosaic), and the
stem and bulb nematode.
Spread
. The seeds are normally released as the fruit
capsule opens during dry weather. They survive
digestion by animals and birds and may thus be
dispersed over large distances. Irrigation water may
carry them along channels and ditches.
Mouse-eared chickweed
is a close relative of
chickweed, but is a perennial, with oval leaves and
many leaf hairs that give the leaves a slightly fluffy
appearance (Figure 17.9). It often grows in turf, lying
close to the soil surface and escaping lawnmower
blades. It prefers damp, poorly drained ground. It
Figure 17.9
Mouse-eared chickweed in turf
