Brassica oleracea italica
This species has been cultivated as a food crop for many hundreds of years and, in that time, several quite distinct forms have arisen. The nomenclature of these forms is confused, to say the least, and by no means universally accepted. We have followed the treatment used by GRIN, though it is very likely to be revised in the future[
Common Name: Broccoli
Sprouting broccoli is a biennial plant, derived in cultivation from the wild cabbage. It grows around 100cm tall, branching freely and producing first a small central head and then many loose axillarly heads of flower buds.
The plant is often cultivated, both commercially and in the garden, for its edible flowering stems.
A cultivated form of Brassica oleracea.
Not known in the wild.
Sprouting broccoli originated through cultivation in the temperate zone, where it can be found at elevations up to 2,000 metres. It grows best in areas where annual daytime temperatures are within the range 15 - 24°c, but can tolerate 3 - 35°c[
]. When dormant, the plant can survive temperatures down to about -5°c, but young growth can be severely damaged at 1°c[
]. Some forms are very cold-hardy, tolerating temperatures down to about -17°c[
]. It prefers a mean annual rainfall in the range 900 - 1,500mm, but tolerates 350 - 2,000mm[
Succeeds in full sun in a well-drained fertile preferably alkaline soil[
]. Prefers a heavy soil[
]. Succeeds in any reasonable soil[
]. Prefers a pH in the range 6 - 6.8, but tolerates 5.5 to 8.5[
]. Succeeds in maritime gardens[
Yields can vary according to variety and growing conditions, but are generally within the range 4 - 10 tonnes per hectare[
Broccoli is closely related to the cauliflowers (Brassica oleracea botrytis) and is often grown for its edible young flowering stems which, by careful selection of varieties, can be available almost all year round from early summer right round to late spring. There are many named varieties and these can be classified into three main groups:-
Calabrese, which matures in summer and autumn. This is the least cold-hardy form. It produces green, or sometimes purple, flowering heads[
]. Some forms will produce a number of side shoots once the main head has been harvested, though other forms seem unable to do this[
Romanesco matures in late summer and the autumn. It has numerous yellowish-green conical groups of buds arranged in spirals[
]. Given a little protection from the cold, it is possible to produce a crop throughout the winter. Unlike the other types of broccoli, romanesco seems unable to produce side shoots once the main head has been harvested[
Sprouting broccoli is the most cold-hardy group. It does not form a central head like the other two groups but instead produces a mass of side shoots from early spring until early summer. The more you harvest these shoots, especially if you do so before the flowers open, then the more shoots the plant produces[
Sprouting broccoli plants come into production in late winter to early spring and can be very heavy bearing over a period of two months or more so long as all the flowering stems are harvested before coming into flower.
Young flowering stems and leaves - raw or cooked[
]. The shoots of sprouting broccoli are harvested when about 10cm long, and before the flowers open, the shoots look somewhat like a small white or purple cauliflower and have a delicious flavour[
]. They are considered to be a gourmet vegetable. When picking the stems, make sure that you leave behind a section of the stem with leaves on it, since the plants will often produce new side shoots from the leaf axils[
Calabrese and Romanesco plants produce a central inflorescence rather like a small cauliflower, which are sometimes followed by a number of smaller flowering shoots. They usually come into bearing in the late summer or autumn and are very productive if they are regularly harvested.
A good companion for celery and other aromatic plants since these seem to reduce insect predations[
]. Grows badly with potatoes, beet and onions[
]. Grows well with potatoes, beet and onions according to another report[
Seed - sow sprouting broccoli in a seedbed outdoors in early spring to May. Plant out in early summer. Do not let the seedlings get overcrowded or they will soon become leggy and will not make such good plants. If your seedlings do get leggy, it is possible to plant them rather deeper into the soil - the buried stems will soon form roots and the plant will be better supported.
Romanesco and calabrese are often sown in situ in the spring.