Ruth Calder, one of Kew's horticulture students, writes about kohl rabi and answers the questions she gets asked most often - “What is it?” and “What can I do with it?"
A purple monster!
Kohl rabi certainly looks odd if you’re not used to it, but the only real mystery is why it’s not more popular, as it’s both easy to grow and delicious.
Close-up of Kohl rabi growing on the Kew horticulture students' vegetable plot (Photo: Ruth Calder)
Perhaps surprisingly, it’s from the same species as cabbage – as are kale, broccoli, cauliflower, Brussels sprouts and others! They’re all varieties of Brassica oleracea, which really highlights how diverse plants can be, even within a single species.
How to grow kohl rabi
Sow the seed ½” deep in rows 20" apart, outside from April onwards, or for cold areas sow inside and plant out later on. It’s said to like a light, free-draining soil and has certainly thrived in the student plots despite a very sandy soil and not much feeding. This is the first year I’ve grown it and I’ve found it an unfussy crop; it likes regular watering to prevent it from either drying out or splitting, and it had a little trouble with both pigeons and aphids, but other than that has been problem-free. It’s quick to mature, being ready to harvest in about eight weeks. Don’t let the stems grow over 3” in diameter, or they become tasteless and woody.
How to eat kohl rabi
The stem has a cabbagey, slightly spicy taste. I usually grate it into a salad, but it’s also good steamed or stir-fried, or in soups and stews. The leaves can also be used in the same way as cabbage leaves. Remember to remove the leaves if you store your kohl rabi for a little while after harvesting – they constantly lose water, which they draw from the stem, causing it to shrivel faster. The same applies to carrots and radishes.
It’s also quite beautiful in a way we don’t expect from brassicas, which don’t have a reputation for being particularly exciting. There’s a less striking green version, but the one we’re growing is ‘Kolobri’, whose vivid purple stems, arching leaf stalks and grey-green leaves would be a lovely addition to a garden even without their culinary merits.
Close-up of Kohl rabi leaf (Photo: Ruth Calder)
It’s one of several vegetables currently brightening up the student plots: we have cut flowers growing too but the vegetables are certainly holding their own in terms of appearance! It makes me wonder if the division between “decorative” and “productive” gardening is a bit artificial, and I will certainly be mixing the two together more in future.
Colourful veg – from left to right: tomato flowers, swiss chard, potato flowers and asparagus pea flowers
Pests and how to deal with them
However, at this time of the year it’s all too easy to lose these treasures to the ever-present army of pests that want to eat our crops before we get to them. Some you may meet with this year are:
- Birds – pigeons in particular have wrought havoc with kohl rabi and nasturtiums on our plots. Deter them by planting plenty of sticks among the plants to stop birds landing, or by using fleece or net – which will also keep away cabbage white butterflies.
Kohl rabi with sticks (Photo: Ruth Calder)
- Aphids – I’m sure gardeners always say this, but it seems to have been a particularly bad year for aphids. So far I’ve found them on the beans, peas, kohl rabi, radishes, nasturtiums, carrots and lettuces, and I no longer dare look at anything else! You can rub them off by hand, or spray with a soap-based insecticide (check it’s safe for food crops!). Flicking them away with a paintbrush is a good way to remove them from tender young shoots without damaging the plants. Whichever method you choose, make sure you do it little and often, so they don’t have time to build up.
- And a happy note to finish on – you may find little semi-circular bites taken from the edges of your broad bean leaves, with no sign of the mystery culprit. The good news is that this is the work of a leaf weevil, Sitona lineatus, which won’t have any impact on your crop – so you can just leave him to his munching!
June Harvest (Photo: Ruth Calder)
Come and buy
Last but not least - after a slow start to the year, produce is finally bursting forth from the plots (see photo above), sometimes in greater amounts than we can cope with, especially for those of us who haven’t yet mastered the art of successional sowing! So do come down to the plots on a Friday lunchtime where you can buy some of the surplus, just a few hours after it’s been harvested. Yum!
- Ruth -
Student Vegetable Plots and weekend 'grow your own' surgeries
Come and admire our extensive vegetable plots, managed by students from Kew's School of Horticulture, and be inspired to get planting yourself! At the weekend, students and apprentices are around to offer visitors advice about seed sowing, transplanting and proven techniques, so you can get the most out of your garden. They'll also be available to answer your questions.
- When are the student vegetable plots open? - all day, during Garden opening hours
- When are the 'grow your own' surgeries' open? - Every Saturday and Sunday, 11am - 4pm
- Price - free, with admission to the Gardens
- Where are the student vegetable plots? - The student vegetable plots are behind the Davies Alpine House at the bottom right of the Kew Gardens map - Plan your visit with the IncrEdibles Voyage map (pdf)
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