One of the most important families of food plants is the Brassicas. Several of them belong to the same species, the extremely variable Brassica Oleracea. What they have in common is that they enjoy soils of about pH 7, so slightly more alkaline than many other plants.
Many descend from the wild cabbage. The ancestor was known as the colewort, an early version, from which came the extremely useful kale. Those of us who have grown this family will be aware that kale seems to be less attractive to slugs than many of its relatives are. This makes it safer to grow as it requires less protection, But descended from colewort was Brassica oleraceae. This one plant species gave us cabbage, Broccoli, calabrese, cauilfower and sprouts, all of which are varieties of a single species. Generally they are robust plants, though Broccoli is hardy to minus 18 degreees, but my last venture into Broccoli coincided with a harsh spell when the weather one night reached minus 21! All dead overnight. With the variable weather that we have been having in the UK I am sticking to hardier varieties.
Also within the Brassicas is kohl rabi. This is newer to production in the UK, but is still Brassica oleraceae. You eat not the leaves, but the swollen stem just above the root. Some people say that it tastes of turnip. I would say that there is some truth in this. Turnip, though, is grown for the swollen root. Its near relative, swede, is also a Brassica; both of them belong to Brassica napus. Oddly, the yellow plant that covers many British fields at the moment, oil seed rape, is also a Brassica napus, but it is grown for its oil, which is useful for cooking.Many people believe that its pollen is particularly effective in causing hay fever. When my son was involved in agriculture in Worcestershire, West Midlands of England he would come out of his house in the morning, smell the rapeseed pollen coming down from the Cotswold Hills and know that his hay fever was coming on.
There are two herbs that come from this family. One is horse radish, the strongest tasting root in the whole family. The other is mustard. It is interesting that the smallest members of the family have the strongest taste, as maybe the taste in larger members is diluted by size.
Brassica rapa is known a pak choi, Chinese cabbage. This is in fact two different subspecies. It has the advantage that it is a plant that can be planted later in summer, as is the case with some other Chinese vegetables.
Brassicas can be susceptible to club root,a fungal disease that causes roots to swell and become less effective. A good defence is to lime the soil and to rotate your plants over a long rotation. Do not grow Brassicas on soil where there is club root for many years. Brassicase are also susceptible to slugs, although kale is the least attractive to them. Another enemy are the two species of cabbage white butterfly, whose caterpillars eat into the leaves. Netting is the best defence. Cabbage root fly lays its eggs near to the cabbage and the larvae burrow into the soil and eat into the roots. Cabbage collars are a useful defence, as they are put round the stem of the plant and thus give the larvae further to travel. They seem to work. Wood pigeons often attack cabbage plants and eat at the heart. . Netting is the best defence.