II.3. BRASSICA CROPS (BRASSICA SPP.) – 165
more susceptible to frost and less tolerant of heat and drought than cabbage. The cultural
requirements of broccoli and cauliflower are similar but broccoli generally grows more
rapidly. Most varieties are now F 1 hybrids.
The broccoli referred to above is more correctly known as “calabrese” broccoli.
It produces a single head and is the form that is of greatest commercial importance.
The “sprouting” broccoli, var. italica, produces a succession of small flowering heads
over an extended period (Figure 3.14) while the “Romanesco” broccoli produces a head
characterised by multiple cone shaped spirals consisting of masses of small flower buds
(Figure 3.15).
Figure 3.14. Sprouting purple broccoli Figure 3.15. Romanesco broccoli.
Source: Courtesy Mr. Fothergill’s Seeds Ltd. UK.B. oleracea var. viridis, collards and kale
The kales and collards are biennials but are usually harvested in the first year for their
edible leaves. They closely resemble their wild cabbage progenitors. Collards have large,
smooth fleshy leaves with smooth margins (Figure 3.16). The leaves of kale are smaller
and thinner than those of collards and many cultivars produce fringed, wavy-edged or
feathery leaves (Figure 3.16). A thick flowering stem up to 1.5 metres tall emerges in the
second year. One form called “Walking Stick” kale produces a tall straight stem which,
when dried and polished, makes a fine walking stick.
Figure 3.16. B. oleracea var. viridis, collard plant (left) and row of kale (right)Source: Courtesy Floridata.