Broccoli, brussels sprouts, cabbage, cauliflower, and kohlrabi are the most commonly grown cole crops. All these species belong to the Brassicaceae (or formerly called Cruciferaceae) family. Brassica oleracea (2n = 18) was the origin species from which all were bred. It is native to Europe and Middle East. A kale-like ancestor was grown in gardens as far back as the time of the Roman Empire. In Europe, cabbage gardens were very important food sources during the Middle Ages. During such a long process of breeding properties of these vegetable species substantially diversified: Brassica oleracea subsp. capitata; subgroup alba; cabbage; heads are formed by infolding of leaves-externally green, internally white:


  • capitata; subgroup rubra; red cabbage; internally white and red. subsp. capitata; subgroup sabauda; savoy cabbage with foliage highly wrinkled or savoyed, green.
  • botrytis; subgroup cauliflora; cauliflower; a tight flower, generally white, some purple.
  • botrytis; subgroup cymosa (italica); broccoli; not as tight, more bud-like individually, blue-green in color.
  • gemmifera;
Brussels sprouts; elongated stem, miniature heads (sprouts) in leaf axils.
Cabbage, brussels sprouts, and kohlrabi are biennials, in the first year they form leaves (and also edible parts) only and in the second year after a period of prolonged cold weather they form stalks with flowers. On the other hand, broccoli and cauliflower have been selected to bloom as annuals and require less chilling to flower, but they will head sooner in cold weather. From the main species cultivated in Europe, Chinese cabbage only was bred from Brassica campestris (2n = 20) that is of Chinese origin and may be annual.

The leaves of all cole crops are covered by layer of waxes that repulses water, which must be considered when using chemical plant protection agents because wetting agents have usually to be added to the pesticide.  In water-stressed plants this layer is usually thicker.
The edible parts may comprise the leaves (cabbage, Chinese cabbage, Brussel sprouts), stalks (kohlrabi) or inflorescence (cauliflower, broccoli). Nutritionally, these species are of great value, because of relatively high content of proteins, minerals and vitamins (broccoli is the best) and low content of fats. All cole crops are characterized by the presence of glucosinate, which gives them after some biochemical activity and characteristic odour and flavour. In high doses it can interfere with iodine uptake and cause glandular enlargement (goitre) in humans. It is noticeable that in cultivated plants the content of glucosinates is much lower than in wild forms.
Small seeds are produced in pods either during the first or the second year of cultivation.
All cole crops grow best at lower temperatures. They usually tolerate very low temperatures and even frosts, and can be cultivated as overwintering crops in areas with mild winter. On the contrary, they don´t usually tolerate high temperatures and special varieties should be chosen if they are intended to be harvested during summer.

There is a wide range of varieties of all these crops: from very early varieties that complete their development in 80-90 days, to those which need about 150 or even more days. Varieties can also be selected for certain shape of edible part, in this respect cabbage is probably the most variable having its heads round, flattened, or pointed, loose or firm, small or large. The colour may also vary as well. For instance, cauliflower curds, in addition to the normal white colour can also be green or violaceous, and for broccoli can be both green or violaceous.
Specially coloured varieties of some cole crops can even be used as ornamentals. Special varieties are also bred for processing or prolonged storage. Breeding to introduce resistance to most important pest and diseases is also used. From the genetic point of view, existing varieties are either populations obtained by classic breeding or F1 hybrids obtained from special parental inbred lines by      crosspollination. In this case all plants derived from one crosspollination are genetically uniform. The advantage of F hybrids is in so called heterosis effect, meaning that the offspring of certain two inbred lines give much higher yield and quality than parental lines. To achieve this effect for each generation of seeds parental lines have to be crosspollinated (it is not possible to further cultivate plants from seeds from F1 generation, because in F2 generation properties of the plants would segregate). For this reason the seeds of F1 hybrids are more expensive, but are preferred because of the plants produced are more vigorous.
1. Figure: Cabbage field. Source: Egor Myznik


In Central Europe, cole crops can be grown outdoors throughout the vegetation period from the end of March to the end of October or beginning of November, and some of them like Brussel sprouts can be left outdoors and harvested even during winter. For early harvest transplants are usually grown in containers in a greenhouse. For later harvest all these species are sown directly into field or transplants are grown in outdoor seedbeds.

2. Figure: Growth development Source: Soha Sabry
Growing of transplants can take 4 - 8 weeks according to conditions. A good transplant should be sturdy with at least three true leaves and good green colour. Leggy transplants, starved transplants or root-bound transplants don't fare well, particularly in the autumn. Physiologically old plants, stressed by high temperatures and/or lack of moisture form after transplanting the edible parts precociously and of poor      quality. Adequate levels of nitrogen in cultivation substrate is very important. levels too low will stress the plants, too high cause misdevelopment of the root system and a higher susceptibility to damping off. Hardening of transplants is essential especially for the earliest plantings when there is high risk of frost. Well-hardened plants can tolerate temperatures as low as - 7 °C for brief periods.
The cole crops grow well in any soil that is well-drained and moisture retentive. Soil should be lighter for early crops and heavier for later crops. Both heavy clay soils and lighter sandy soils can be improved by adding organic matter. The optimum pH range for cole crops is between 6 and 6.5. Liming the soil will increase the pH of acid soils. It is important as prevention of some diseases like damping off and club root. Proper watering can mean the difference between good production and poor production. Vegetables need 25 - 40 mm of water from rainfall or irrigation each week during the growing season. Always soak the soil thoroughly when watering. There is little or no value in a light watering that only wets the surface of the soil. Very sandy soils may require more frequent watering.
The edible parts of water-stressed plants are of reduced quality. For instance, in kohlrabi the  tissues become woody and inedible. Fertilization is essential for good yield and quality. Cole crops, especially cauliflower and broccoli, must form a lot of leaves prior to forming of edible part, otherwise it will be of poor good quality. For this a lot of nitrogen is needed in part this can be supplied in the form of animal manure. Cole crops need a relatively high amount of boron (attention on recently limed fields) and cauliflower and broccoli have special demand for molybdenum. Cole crops are often cultivated in a short crop rotation (sometimes even every year) and in this case the proper fertilization is especially important. Cauliflower must be blanched to maintain the desired white head. To blanch, tie the leaves up around the head as soon as the small curds are 5 cm across. Some processing varieties are also self-blanching. They are not so white as those produced for the fresh market, but the labour required for tying is eliminated.
From the phytopathological point of view it is important that all cole crops can be infected by the same pathogens and damaged by the same pests, even though the susceptibility of different crops to certain pests and pathogens differs. After harvest, all plant residues should be ploughed under to prevent the spread of pests and diseases. However, if clubroot occurs on the field, the infected roots should be removed and burned.
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