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Cauliflower and Kohlrabi


Brassica oleracea, Botrytis Group

Cauliflowers are clusters of buds of cabbage flowers, selectively bred to grow into firm curds before the full flowering stage. The word cauliflower is from the Latin caulis (cabbage) and flōs (flower).

They were first written about in Roman times and then were much grown in mediaeval Cyprus. During the 16th century, there are first mentions of Romanesco broccoli, which is actually a cauliflower. They are pale green, while recent breeding has given us cauliflower curds of varied colour.

Cauliflowers are mostly annual, but not exclusively. I have grouped them in this lesson with family relation kohlrabi, because both of these vegetables have a similar time pattern of growth, just for a totally different result!

Cauliflowers (and kohlrabi) grow extremely well in no dig soil, as the gardeners and presenters discovered in 2016–18 at the BBC Beechgrove Gardens in Scotland. They ran a trial of vegetables in dig and no dig beds, and started off feeling sceptical. Soon they were, and continue to be, enthusiastic for no dig, as you can imagine from the photo below comparing cauliflowers – dig on the left and no dig on right.

A very beautiful Graffiti cauliflower, cut in half – this one is not yet fully mature, but is still striking and was super tasty
Jim McColl’s write up of the success of a no dig trial at the BBC Beechgrove Gardens – Aberdeen Press and Journal, November 2017
Graffiti cauliflower cooked two ways – roasted on the left, and boiled with French beans on the right; you’ll notice how the anthocyanin colour has not been washed out by boiling water

Harvest period

  • Days from seed to first harvest: 100–150 for annuals, 270 for biennials.

  • Best climate is moist, not dry, temperate without extreme heat.

Why grow them

There is something special about seeing the emergence of a small cauliflower in the middle of a huge mass of leaves. Then to watch it turn into a beautiful and tasty harvest.

Cauliflower plants are demanding for the results we desire, and need fertile soil plus temperate weather. They pose a challenge, but it’s worth the attempt for harvests of great flavour, colour and beauty.

  • Each variety needs sowing at its best times.
  • They need fertile soil.
  • They are vulnerable to insects.

When you succeed, you know you are a good gardener.

Suitable for containers/shade?

You can grow cauliflower in shade, but I do not recommend growing them in containers because of their size. The harvest of food, per square metre and time needed, is relatively low, and I see them as a luxury. You may disagree!


The nomenclature varies and can be confusing. Sometimes one sees the phrase ‘Italian cauliflowers’, which include Romanesco and all kinds of different coloured cauliflowers. In this lesson, my main differentiation is between annual and biennial types of cauliflower. There are four common colours: white, purple, orange-yellow and green.

Mid-April – these impressive Aalsmeer cauliflowers are fully formed, sown the previous July
A striking Grafitti in late June, from a sowing in late February
This fully formed, medium-sized Sunset cauliflower was sown in late February, and is now ready for harvest in mid-June


Read the small print for each variety to check the maturity time, because they all take a slightly different amount of time from seed to harvest. Many good varieties are hybrids now.

You have exotic colour choices, all of which are hybrids. Graffiti is best for a fast-maturing purple cauliflower. Its colour is from anthocyanin and survives boiling in water, unlike purple broccoli which turns green when boiled.

For green curds try Trevi, and for orange I like Sunset. The orange colour comes from beta carotene or vitamin A.

The old open-pollinated variety All Year Round can be sown from February onwards and is reliable, if not remarkable.

Clapton F1 is white and claims resistance to clubroot.

For Romanesco, I have found recently that the old open-pollinated varieties are giving smaller heads. I recommend hybrids such as Celio and Navona.

Romanesco Navona in mid-November from a sowing in June – the head is fully mature; some Kaibroc broccoli on the right
Romanesco here in early January, sown in mid-June; although the head is pretty, it is small – an open-pollinated Natalino
Romanesco weathering a -2 °C/28 °F frost in November, using its own leaves to protect from the chill; below -4° C/25 °F there is some frost damage


Walcheren, Aalsmeer and Medallion F1 are examples of the many varieties you can grow to overwinter, from sowings in late June to early July. In seasonal terms that means sow before midsummer, for harvest in early to mid-spring.

Maybach F1 can be sown in October/early to mid-autumn, to overwinter as a small plant in a pot in the greenhouse, and then transplant in March for cropping in May.

Purple Cape F1 is both beautiful and productive, and is also hardy in temperatures as low as -15 °C/5 °F, before the curding stage in early spring,

Aalsmeer cauliflower, originally sown in July, now looking a bit limp in a February frost – the temperature is -9° C/16 °F
The same Aalsmeer on 10th April, now starting to form lovely curds
By 1st May the Aalsmeer has a magnificent head – it’s a fantastic vegetable for the hungry gap

sow & propagate
Transplant - Size, time of year, Spacing, support
container growing
Prune and train plants/thin fruit
Harvest times and method
Potential problems


Simply twist each stem firmly, to remove it with a few large roots, leaving the rest in the bed. In dry weather, I find it’s worth walking on the bed after any such removal, when it has caused unwanted loosening of soil.

A summer harvest of calabrese and Sunset cauliflower, while the Cabbice cabbage are still growing in the soil – these plants were all transplanted at the same time, with 40 cm/16 in spacing, although you see they all finish at slightly different time
Interplanted leeks with cauliflowers in June – the cauliflowers will mature in a month, whilst the leeks will start growing slowly, before accelerating later
12th July – in summertime the garden is changing quickly; top left are new dwarf bean plants, transplanted today after cauliflower; you can also see courgettes, celery, and a new planting of broccoli, made after we had cleared broad beans

Follow with

Usually one clears ground completely before the next planting. See the photo above showing how we experimented with planting leeks between cauliflowers. This did work, although the leeks struggled for their first month until we cleared the cauliflower plants, and they took time to grow strongly.

Summer harvests can be followed by French beans, salad onions, chard, beetroot and many salads.



Brassica oleracea, Gongylodes Group

I apologise, to German readers especially, for giving kohlrabi a small, but sweet, mention. It's an amazing vegetable, with the swelling of its stem just above soil level being the part that we value and eat. It is sometimes mistakenly considered a root vegetable.

Kohlrabi is of the Brassica family, and susceptible to the same pests. It is strictly an annual, often maturing in half a year, and keen to flower in springtime, according to variety.

Kohlrabi is sometimes compared to turnip. This is totally unfair because the flavour is way more agreeable, the texture is firmer, and it's tasty both cooked and in salad. The main thing to beware of is woodiness, which happens only in early summer, the time when flowering initiates.

Harvests in temperate climates are best either before midsummer, from sowing very early, or in late autumn through winter from summer sowings.

  • The first, early sowing date can provide about six weeks of harvest before midsummer.
  • Summer sowings can give six months of harvest, plus the possibility of storage in autumn and winter.
  • Kohlrabi are beautiful plants, floating their swelling stems above the ground.
Azur Star kohlrabi on 17th May, now three months old and about two weeks from harvest; they had fleece over until early May

Early Purple kohlrabi in late May, sown under cover in mid-February and transplanted in mid-March, then with fleece over; a first harvest could be taken now
Late November – a 15.9 kg/35 lb harvest of Superschmeltz kohlrabi is ready for storage; these came from 15 plants, sown in early July and transplanted in late July

Raise plants as for cauliflower, and transplant at 30 cm/12 in.

Pests are the same as for cauliflower. A fleece cover helps spring plantings to grow in warmth, and keeps off many insects. Summer plantings benefit from a mesh cover for their first month.

See the average growth of 19-day-old kohlrabi in late July
These kohlrabi have been planted in late July after clearing lettuce – here you see them without any protection after five days; some were then eaten, so I covered them
Late July – these Superschmeltz and Blaril kohlrabi have been transplanted after a crop of onions
12th August – see the dig (furthest away) and no dig trial beds, growing kohlrabi in the middle, now 17 days since transplanting; in addition to this we have, from left, French beans, cucumber, carrots, kale, celery, beetroot, leeks, chicory and celeriac
By 12th October you see how the kohlrabi has grown, with Superschmeltz in front and Blaril behind; the no dig bed is on the right
Kossak F1 kohlrabi on the right, with vegetables  to store in late November

Kohlrabi are frost-hardy, although I don't know the lowest temperature possible. Mine have survived to -6 °C/21 °F, the coldest it usually gets here in winter. I leave them in the garden, but they also store well in a crate, from harvesting in early winter.

  • A problem can be splitting across the top, which is maddening in a first sowing when a proportion of the fine kohlrabi suddenly open up. There is still an edible harvest, just less of it, and this seems to follow periods of uneven soil moisture. Keep them well-watered in spring.
January – kohlrabi, at the front, are ready any time in winter, and the cauliflower behind will make curds in spring

October – a split kohlrabi, Kossak F1, sown in July; most of it is still edible!