What are Brassicas?
The cabbage tribe is one of the most important families in the plot including
cabbages, kale and cauliflowers, Brussels sprouts, broccoli and calabrese
along with swedes, turnips, radish and mustard.
The reason the brassica family is so important is that they can provide
a fresh staple on any day of the year.
Brassicas are usually a leaf vegetable and they require plenty of nitrogen
fuel that growth. They all share a love of lime along with a constant supply
of water which is best served from ground rich in humus. They are less tolerant
than many other crops and meeting these requirements can be difficult but
the rewards are there if you succeed.
Creating the ideal brassica bed
The ideal brassica bed needs both nitrogen and humus so the addition of manure
in autumn will accomplish both. Dig over the soil and then add a barrow load
of manure per square metre to the land. You can even add more if you wish,
some of the best brassica growers add twice that amount of manure.
Leave the manure over the winter to give the worms a chance to take some
down into the soil. In the early spring fork over the top 15cm of the soil
to mix the manure in or run over with a rotovator and leave for a week to
settle.
Now adding the manure will have had the effect of making the soil more acid
and if any plant does not like an acid soil it is the brassica. If you can
do, test the pH to measure the acidity and add the appropriate amount of lime
to take the level up to 7.0.
If it goes a little higher it will not matter
so if you cannot test just add about a kilogram per square metre on a
clay soil with about half that on a sandy soil and leave this to weather in
for a couple of weeks.This is more information on garden lime here.
Never add lime and manure at the same time because they react together and
benefit neither. By adding manure in the autumn and lime in the spring, sufficient
time will have elapsed,
to prevent trouble.
Fertiliser Requirements of Brassicas
You now have a near perfect brassica bed but they are a greedy crop and adding
60 grams per square metre of a general purpose fertiliser such as Growmore
or Fish, Blood and Bone before planting out will benefit them.
Most failures with the cabbage tribe come down to lack of nutrition so if you
cannot provide loads of manure, add additional fertiliser.
With Brussels sprouts that require a long growing season, an additional boost
mid-season will often make a dramatic difference to the final crop.
Since
they are producing leaves, albeit wrapped up tight with the sprout, it
is nitrogen they are most likely short of. A sprinkling of dried blood or
sulphate of ammonia around the base of the plant will provide that additional
nitrogen midway through the growing period
If the plants do not seem to be doing well and the cause is not a disease or
pest then feeding with a high nitrogen liquid fertiliser will often save
the day with any of the brassica family.
Brassica Pests & Problems
The worst problem that affects the entire brassica family, except the salad
radish which grows too quickly to notice, is without doubt club root disease, Plasmodiophora
brassica. This is easily spread and once in the soil can remain for up
to 8 years.
Brassicas are also attacked by the cabbage
root fly, this little pest lays
its eggs by the stem and the little maggots that develop then attack the roots
resulting in stunted growth or death.
If you manage to cope with the club root and keep the fly off, then you still
have problems to manage. Slugs love some of the brassica family, especially
cabbage and cauliflower so you need to keep them away. Pigeons find brassicas
a tasty treat, especially in the winter months when little else is on the
plot so netting to keep them off is necessary.
Finally, there's a reason it is called the cabbage white butterfly. In the
summer months the caterpillars can devastate the crop, but they are quite
easy to destroy.
More on Brassicas
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