GROWTH CONDITIONS
Growth period: highly variable, depending on type and variety, and growing
conditions.
C frost. In
hot, dry regions they are grown in the cooler season and/or at high altitudes, as they
grow poorly in heat.
Rainfall: medium-high rainfall regions are ideal. Drought affects the plants badly,
which should not suffer any check to their growth. Irrigate if possible whenever dry.
Altitude: in the tropics cabbages are grown in the highlands.
Pests: cabbages are extremely attractive to insects; often the worst damage is caused
by the Cabbage root fly, which causes plants to wilt, sometimes also to develop
bluish leaves with yellow edges, and occasional death. The larvae burrow down
from the soil surface, then into the roots and stem, which they attack at ground level.
The best control is by placing a “collar” of material such as roofing felt, carpet—
preferably greased or paraffined—around individual plants. A square of about 15 cm
is enough for the collars. Some control also comes from applying high N fertiliser,
supporting the plants by banking up soil around their stems, hoeing or moving the
soil regularly so that birds can find and eat the larvae—and destroying all infected
plants.
Large and Small Cabbage White butterflies commonly attack all Brassicas.
Caterpillars of the Large White are yellow and black and highly conspicuous as they
also feed on the upper side of leaves. The Small White’s however are small and
green and inconspicuous. Both can either be picked off and dealt with, or sprayed
with a salt solution, which also deters slugs.
Cabbage Moth larvae eat the central leaves, control with derris or pyrethrum.
Cabbage White fly look similar to the greenhouse whitefly. They overwinter on
Brassicas; eggs look like small brown scales and are laid on the lower leaves, which
should be removed.
The flies can be discouraged by planting lovage and/or fennel near to the
cabbage plants, which attract the parasitic wasps Aphelinus.
Leatherjackets are grey-brown, legless larvae of Daddy Long-legs which
sometimes eat seedling roots, causing the plants to wilt and die. Dig or plough soil
several times to allow birds to eat the larvae.
Cutworms are very small worms which eat small plants at the ground level. Control
with a collar—as for root fly control—or pile wood ash around the stems.
Diseases: if the dreaded Clubroot disease is present in your soil, you have a
problem, as the fungal spores can lie dormant for at least seven years. The roots
become large and malformed, and look similar to cabbage gall weevil damage,
identified by cutting open the root galls and looking for the larvae. Plants may wilt
and even die. Control or minimise spread by rotation, no Cruciferae of any kind,
including shepherd’s purse or charlock, for at least four years. Apply lime to acidic
soils, burn all infected roots and never put Brassica roots on the compost heap. One
ingenious method is to spray soil that is not planted with Cruciferae, but may be
planted later on, with water in which Brassica plants have been boiled. This
stimulates the fungal spores to break dormancy, but they will soon die because there
are no suitable Cruciferae to live on. Clubroot is mainly a problem of the temperate
regions. In the tropics, Blackleg, Black Rot, Downy Mildew and Cabbage Mosaic
Virus can devastate crops of cabbage equally badly.
Temperature: varieties adapted to temperate regions can withstand 7–°