Growing broccoli

Many of the techniques described for cabbage and cauliflower apply to broccoli.

A well-formed head grown in mid-summer.
Photo: Bill Kerr

Broccoli has become a far more important crop of late due to its reported health benefits, especially as a source of anti-cancer substances. In this regard it is superior to cabbage, but not as good as kale. Broccoli is also much easier to grow than before. It was once exceedingly difficult to produce marketable broccoli from spring right through summer, and the heads that did grow were smaller and of lower quality.

Like cauliflower, it was regarded as cool-season crop, but breeders have since developed varieties that thrive in the heat
(and suffer in the cold). In short, seasonal factors have been eliminated to make broccoli available all year round. In the US, farmers plant a higher population of broccoli per hectare and harvest when the heads are still somewhat immature. The market also requires a thick stem.

Harvesting is usually done with a specially designed, self-propelled harvester. Pickers cut the broccoli and load it onto conveyers. Uniformity to maturity is therefore most important. Another worker further along picks up three stalks at a time and places them into a hole on a machine that wraps a band with the farm logo on it around the stalks and trims them to the same length. These are then placed into a carton ready for the market.

Certain broccoli cultivars are bred to form side-shoots, whereas side-shoots have been selected out of other cultivars. Some producers prefer side-shoots as these develop from the leaf axils (the upper angle between a leaf and a stem) after the main head is cut and provide a second crop. In South Africa, the cost of labour has reduced the practice of harvesting side-shoots.

Some varieties produce sprouts or spears and do not make a main head at all. The leaves can be marketed in bunches and are prepared and eaten like spinach.

Heads vs side-shoots
This crop goes into a reproductive phase in spring and most varieties form a smaller head from a smaller plant at this time with a larger concentration of more advanced side-shoots. Although it has been claimed that these side-shoots do not influence the main head size, they certainly do. For this reason, they are often removed by hand when the plant is half-grown so that all the energy from the leaves is concentrated on the main head.

As with cauliflower, this crop does not tolerate stress very well. Although the plant may look healthy enough, the stress will manifest in the head development.

Symptoms

Stress symptoms include the following:

  • Uneven bead development
  • Large and small beads are found on the same floret. In addition, some beads open prematurely.
  • Discolouration of beads
  • The beads may vary between yellow, brown and purple.
  • Uneven floret development

In this case, the head is not smooth and uniform.

Bract leaves

These are small leaves that grow in the head between the florets. In a variety that does not mature uniformly, a stress period (a heat wave, for example) can affect the early heads, leading to stress symptoms, while the later developers that escape the stress can grow perfectly healthy heads.

Nitrogen requirements

Broccoli does not require as much nitrogen as cabbage or cauliflower. These two crops need three or four top dressings; broccoli usually requires no more than two. Bear in mind that modern varieties mature fairly rapidly: they are ready 60 to 80 days after transplanting.