What could be better than a plant that is easy to grow, low maintenance, tasty, extremely nutritious and decorative too? Kale has all these qualities. Once regarded mainly as cattle feed, this neglected brassica is now a sought after superfood, renowned for its high concentration of healthy antioxidants.
Inspired by a surge in new kale varieties to meet consumer interest, the RHS Vegetable Forum decided to hold a new kale trial this year on Wisley’s Trials Field. The Forum is assessing the kale for yield, uniformity of crop, texture, weather resistance, disease tolerance, robustness and flavour.
But kale is not only a nutritious vegetable; some varieties are highly ornamental too, so don’t just save them for the vegetable garden. They look great in containers by the front door (for easy picking too) or in a winter bedding scheme. The leaves can even be used in flower arranging. A good ornamental variety is ‘Cavolo Nero’, a black kale originally from Italy, with luxuriant dark green, almost black, upright leaves with a ‘bubbled’ texture. Another great variety is ‘Redbor’ AGM with frilly purple leaves and dark purple-red veins that intensify in colour as the weather gets colder (at least one thing to look forward to as the frosts arrive).
Another great feature of kale is that it can be continuously cropped through the winter by picking off the tender young leaves. These can be steamed, but personally I love the crispy texture and nutty taste when the leaves are stir-fried for a few minutes in olive oil. Or try them in TV Masterchef Greg Wallace’s recipe for chilli greens.
How to grow kale
Kale is easy to grow. We sowed our seed in pans in the glasshouse and pricked them out into small biodegradable pots. These were hardened off six weeks later then planted out, still in their pots to avoid root disturbance. They were planted 60cm (2ft) apart in a bed covered with landscape fabric to suppress weeds and help retain soil moisture. We used brassica collars on each plant to help protect against cabbage root fly – the fly lays its eggs on the cardboard collars where they dry out. To prevent fungal diseases we removed yellow leaves from the base of the plants.
Pigeons can decimate kale crops, so we covered our trial – all 30×10m (90×30ft) of it – with netting held up by wooden posts. This year we're using irrometers in the kale and Brussels sprout trial. These gauges give a precise measurement of soil moisture content and hence the amount of water required – which hasn’t been much in the recent torrential rain!