Cruciferous Craze – Vegetables for Health
First it was broccoli, then kale, and now it is cauliflower that has assumed super-star status for its culinary qualities and health benefits. Cruciferous vegetables, a group that includes the brassica mafia as well as leafy Asian greens, rocket, kohlrabi and roots like radishes and turnips, dominate the winter veggie garden. March is the main month for planting. Long crops like broccoli, Brussels sprouts and cauliflower should have already been sown, but plants in seedling trays can still be set out.
Health recap Just how good are they for us? Most cruciferous veggies are high in fibre, essential minerals, vitamins (like A, C, K and E, which strengthen the immune system), and, most importantly, phytonutrients, which studies suggest could reduce the risk of cancer if vegetables are eaten in adequate amounts.
While recent research has not found a strong enough or consistent enough link, new research is investigating whether genetics may play a role in the effectiveness of the beneficial anti-cancer compounds in these vegetables. How much is enough? According to the US Department of Agriculture, the recommended consumption of cruciferous veggies is one cup of cooked vegetables a day or two cups of raw vegetables.
Word of warning: eating excessive amounts can impair thyroid function.
Degrees of difficulty in growing cruciferous vegetables
Of all the veggies, cruciferous veggies are the most demanding. They need well composted, fertile soil, monthly fertilising and consistently moist soil through regular watering. If you don’t deliver, they won’t perform as they should. The divas are broccoli, cauliflower, cabbage and Brussels sprouts, and they all have their likes and dislikes. The easy-going members of the family are Asian greens, kale, kohlrabi, radishes, rocket and turnips.
Commonly grown cruciferous crops, on a subjective scale from easiest to hardest to grow.
Quick and easy Rocket: This mustardy salad green can be grown all year but does best in cooler months. Sow thickly and cover with a light layer of soil that’s firmed down and watered. The seed germinates quickly and the leaves can be harvested within a month.
Health note: Besides its vitamin content, rocket contains calcium that is important for bone and tooth health, and muscle and nerve function.
Radishes, tangy, crunchy veggies for salads and sandwiches, are another quick crop. Sow the seed in a position that receives full sun, or in a container. Keep the soil moist during germination (5 – 7 days). Uneven or irregular watering can cause radishes to split. Sow a new batch every 10 – 14 days.
Health note: Radishes have a detoxing action that helps to cleanse the liver and stomach.
No special treatment needed Kale is a dream vegetable. It is not usually bothered by aphids or diseases, and cold weather gives the leaves a sweeter taste. Besides the tall-growing kale (leaves picked from the bottom upwards) newer varieties are compact and leafier. Like Swiss chard, pick the outer, young leaves. Kale likes slightly acidic soil and full sun or partial shade.
Health note: Kale (raw, cooked or in smoothies) has the highest level of vitamins and calcium among the cruciferous vegetables. Asian greens include bok choi, tatsoi and mizuna, which are light, mustardy greens for salads, stir-fries and soups. The pungent mustards are ‘Japanese Giant Red Mustard’, ‘Red Frills’ and ‘Green in Snow’. Harvest the outer leaves regularly or cut off the whole plant and let the stub regrow. Eradicate cabbage caterpillar with an organic insecticide like Margaret Roberts Biological Insecticide.
Health note: They are a good source of vitamins A, C and K. Steam or sauté stronger tasting greens with olive oil for a milder flavour.
Kohlrabi is a quick crop that doesn’t need any special treatment. The ‘bulb’, which is the swollen, fleshy stem that develops just above the ground, is milder and sweeter than cabbage, although the bulbs will be tougher from drought-stressed plants. Harvest kohlrabi when the bulb is between the size of a golf and a tennis ball (5 – 7cm in diameter). The bigger it gets the more fibrous it becomes.
Health note: Its high fibre content assists the digestive process and helps with weight loss, helping to give that ‘full’ feeling.
Challenging but worth the effort Broccoli’s most important requirements are full sun and regular watering so that plants don’t wilt, as this affects the size of the head. Top dress with a nitrogen-rich fertiliser two weeks after planting and again after four weeks. Pick the head before flowers develop.
Health note: Both stalks and florets are nutritious, and cooking (preferably steaming) makes the nutrients optimally available.
Brussels sprouts need preventative spraying for aphids because the sprouts spoil or become very bitter if infested by aphids. Fertilise during their growth phase to allow them to grow up to 1m high before being tipped off. That helps to push their energy into developing the fruit.
Health note: A good source of fibre and antioxidants, especially kaempferol, which reduces inflammation and promotes heart health. Roast or braise for best flavour.
Cabbage needs plenty of space to grow, and it too is attacked by aphids that can get into the head and spoil the crop. Spray preventatively with an organic insecticide like Ludwig’s Insect Spray. For healthy, well-sized cabbage heads pay attention to Broccoli Cabbage watering, fertilising and pest control in July and August.
Health note: Keeping the cabbage cold helps to retain its vitamin C content. Store in an airtight container in the refrigerator.
Cauliflower is a long crop with a four month growing period. Water regularly so that the soil doesn’t dry out, which can result in deformed heads, and fertilise every two weeks with a nitrogen-rich fertiliser. As the seedlings grow, mound up the soil around them to prevent them from falling over. mound up the soil around them to prevent them from falling over.
Health note: Low on calories and a good alternative for gluten-free diets. It contains sulforaphane, which is an anti-cancer compound that is released when the cauliflower is chopped or chewed. Steaming and stir-frying lead to lower nutrient losses than boiling