Broccoli

Brassica oleracea var. italica

The country of Italy features strongly with broccoli. The word is plural of ‘broccolo’, meaning ‘flowering sprouts of cabbage’.

Introduction

A member of the cabbage family.

The country of Italy features strongly with broccoli. The word is plural of ‘broccolo’, meaning ‘flowering sprouts of cabbage’. These sprouts are naturally thin and long, so broccoli is the result of breeding to increase their size and tenderness.

Types

There are three main ones, with significant differences in harvest amounts, size, types of size, and timing.

1st June – first harvest of calabrese, sown under covers in late February

Kaibroc in November – these small plants were interplanted in August between lettuce which grew for six more weeks, hence their small size; however they are still looking vigorous

7th April – Claret F1 purple sprouting broccoli, looking pretty in the frost after surviving the winter

1. Calabrese

The largest and most tender broccoli, from Calabria, the southern toe of Italy’s boot shape on a map. A large domed head is your first pick, followed by side shoots over a few weeks.

2. Kaibroc

What I call ‘kaibroc’ is also called ‘brokali’ and ‘broccolini’, sometimes ‘tender stem broccoli’ too. It’s a hybrid cross of broccoli with kailaan or gai lan. The latter is sometimes called Chinese kale (Brassica oleracea, Alboglabra Group), an extremely fast-growing plant for harvests of flowering broccoli with thin stems.

Kaibroc’s stems are of medium thickness, and it can give the first harvest as quickly as two months from sowing. Late summer sowings crop well into winter if not too frosty.

Another hybrid variation is Broccoli raab, or Cima di Rapa/Rapini (Brassica rapa var. Ruvo). More of this plant is edible than most of the broccoli here – the leaves are very tender while its shoots are smaller. It overwinters in temperate climates, for pest-free harvests in early spring. Summer sowing is less advisable, as shown in the second photo below.

Late March – Broccoli Raab in Steph Hafferty’s polytunnel; this was sown in September and has cropped already with tender shoots and leaves – almost no pest damage at this time of year

Broccoli Raab in summer from a July sowing, struggling against pests – it is better sown late August for autumn harvests outside, in September for overwintering undercover, or outside in mild climates

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3. Sprouting broccoli

Older strains of broccoli grow a medium-sized first head, followed by many smaller second stems over weeks, even months. With each succeeding pick, the stems are thinner and slightly more fibrous, plus greater in number. The flower buds may be green, white, or purple.

I use purple sprouting as the example in my video shown below, of the type which overwinters, to crop in late winter or early spring. The purple types are common, white ones less so, and they yield a little less too.

A variation is the Nine Star Perennial (photos below), which, in my view, is not a true perennial because it needs picking hard through spring to make sure no flowers remain. If left to flower through summer, I have found it less likely to survive. It’s interesting to compare it with perennial kale, which does not flower and keeps sending energy to the leaves in a seamless way, throughout the year.

9th June – magnificent main head of calabrese Marathon F1, sown on 25th February; this is ready to cut, and within a few days would be elongating, and even have flowerbeds opening

Kaibroc transplanted on 10th July, after the main head has already been picked; this is late September – many harvests are still to come

30th March – Claret F1 broccoli with an impressive main head after a mild winter; this would be harvested two to three weeks later, after a cold winter

Harvest period

Days from seed to first harvest: 70 for kaibroc, 100–130 for calabrese, 170–300 for sprouting broccoli.
Broccoli as an annual: June to November from two sowings.
Broccoli overwintered: March to May.

Calabrese seeds sownCalabrese ready to harvestLate winter to mid-springThrough early summer, smaller heads each harvestEarly summerThrough autumn until moderate frost

Kaibroc seeds sownKaibroc ready to harvestLate winter to early springLate spring to early summerMidsummerMid-autumn, winter if not too cold

Sprouting broccoli seeds sownSprouting broccoli ready to harvestSpringMidsummer and through autumnEarly summerThe following spring

Best climate is warm not hot, with good moisture or water given; they tolerate freezing.

Why grow them

Continuous cropping is one of the biggest advantages. From one sowing, you can have a fine and large main head followed by side shoots for four to six weeks. Even for longer, especially if you don’t mind them being small and with thin stems.

With homegrown broccoli, you can pick stems with more length than you might find in the shops. The sweetness is in the stems much more than in the buds. One old description of broccoli is ‘poor man’s asparagus’.
You have seasonal choices, with harvests possible almost year-round in temperate climates. Broccoli plants are impressively cold resistant.
An extra harvest is the leaves. The ones high up and closest to any broccoli buds are the most tender, just don’t take too many if you want plenty of broccoli.

April – Nine Star Perennial broccoli; the first heads are now ready, from a transplant the previous July

See how the Nine Star Perennial broccoli looks like a cauliflower at this stage, before a mid-April harvest

Suitable for containers/shade?

Broccoli grows fine in shade, while for containers I suggest kaibroc because it is smaller. Or even kailaan, for harvests of flowering stems and leaves.

Varieties

Hybrid varieties of calabrese give the large green heads you see in my photos, and I find only small variations between varieties. Try any of Belstar, Fiesta, Green Magic, Ironman and Marathon.
Kaibroc/brokali are all hybrid varieties. Good ones are Apollo, Atlantis, Columbia and Royal Tenderette.
For sprouting broccoli, check the small print about timings of harvest in any varietal description – they vary a lot. My favourite is Carmen F1, for harvests in early spring from sowings the previous summer.

Other good hybrids of sprouting broccoli are Rudoph, which crops mid-winter if not too cold, and Summer Purple, for harvests from midsummer through autumn. Hybrids give larger heads than the older open-pollinated varieties such as Early/Late Purple Sprouting, which are now often poorly maintained by seed companies.

For white sprouting, try Burbank F1 to crop late winter, and Nine Star Perennial for early spring.

Calabrese Fiesta is bountiful by 16th June, from an early sowing in late February

Brokali Apollo from an early sowing, the first small heads showing on 10th May; harvests of kaibroc are smaller in spring than in autumn

7th April – slight -2 °C/28 °F frost looking pretty on Claret F1 purple broccoli

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Sow and propagate

Seeds appear in three to seven days, depending on warmth. They are definitely worth raising under cover because of all the possible insects that eat brassica seedlings. Also, you may well be growing hybrid varieties, whose seed is expensive. Plus if you lose a sowing, you have lost critical time which can't be replaced, as well as valuable seeds.

Propagation/sowing conditions

Germination happens in a wide range of temperatures, say 10–32 °C /50–90 °F, and is particularly strong in summer months. This follows from the lifecycle of brassica plants: they flower in spring and drop seeds in early summer, then grow again.

25th June – a range of summer seedlings in the greenhouse include broccoli, lettuce, and swede at the back

The first step – here I am sowing about 60 seeds for 40 eventual plants; I shall prick them out five days later into module cells

30th June – summer sowings of purple sprouting, calabrese, chicory, fava bean, and beetroot

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Sowing time

Mid-February, or late winter, is the time to sow under cover, in warmth. Make sure that your variety description is for cropping in early summer, not autumn. The earliest sowings have a chance to grow and crop before butterflies arrive.

Broccoli to crop in autumn does well from sowing in early summer, as do varieties for cropping in the following spring.
The best two times to sow kaibroc are late winter and midsummer. Try a few dates to find the best ones for your climate.
Other sowing times are possible, but the ones I give are for strongest growth, with relatively less insect damage.

Sowing method

With the aim of having only vigorous plants, rather than a random mix of stronger and weaker ones, it's worth sowing in a small tray, from which you can prick out the strongest seedlings into modules, one per module.

Seedlings are easiest to prick at four to five days old, when you see only the cotyledon leaves.
Please ignore the common advice to prick out after you see a first true leaf, which actually makes it difficult because seedlings already have a lot of root. It takes longer and results in more root disturbance.
Or sow two seeds per module and thin to the strongest. However, this means you need more seeds and lose the chance to bury stems when pricking out, so seedlings will be more leggy.

Brassica seedlings pricked out in late winter, so germination was slower – they were sown 11 days earlier in mid-February

5th March – a tray sown with cabbage and calabrese, from which I had already pricked out seedlings; on the right are multisown turnips

Propagation in early spring – these seedlings have been on the hotbed for 20 days

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In a 2.5 cm/1 in module, plants could be ready within two weeks from pricking out, and in a 4 cm/1.5 in module you have about another week before transplanting. There is leeway with brassicas because they tolerate an amazing amount of neglect, such as running out of nutrients in compost before being transplanted, after which they always recover.

Nonetheless, best growth is from minimum interruption, as far as possible. Transplant as soon as they are ready, before you see yellowing of the cotyledon leaves.

Pot on?

Not usually necessary, except for summer sowings if you are waiting for a preceding vegetable to finish. Interplanting the broccoli between a soon-to-finish vegetable, say onions, may be an option instead of potting on.

Transplant/interplant

Transplant size

Any height from 10–15 cm/4–6 in is good, and it’s easier plus quicker to transplant brassicas at the smaller end of that range. Set plants deep enough for most of their long stem to be below surface level. It’s fine to bury the cotyledon leaves if they are still there.

Transplant time

Broccoli plants are hardy, so your first sowings of late winter can go out in late March, without hardening off. Cover with fleece which can lie directly on the plants, to hold warmth close. This also serves to keep off pigeons and cabbage root flies.

Plants in summer will encounter many pests, and they are best covered against insects. We use mesh supported on hoops.

3rd May – removing fleece covers from onions, calabrese and lettuce, after a cold April

Green Magic F1 calabrese, 25 days since being transplanted and growing well – here briefly uncovered on 17th April to pull a few weeds

The same Green Magic F1 plants just 11 days later on 28th April, after benefiting from some rain

The broccoli bed looking a little worse for wear during a -2 °/28 °F frost

26th May – first harvest from the Small Garden, the start of an exciting and suddenly plentiful time of year

26th May – broccoli and bean beds, from both of which I’d already had excellent harvests

Spacing

There is a range of spacings, according to the types of broccoli. Also, wider spacing is for longer-lived plants and larger heads. With calabrese, for example, you can plant at 40 cm/16 in, for fewer plants with a substantial first head and four to eight weeks of side shoots, compared to 30 cm/12 in for more plants with medium heads and three to four weeks of side shoots.

Calabrese: 30–40 cm/12–16 in
Kaibroc: 30 cm/12 in
Sprouting broccoli: 45–50 cm/18–20 in

The wide spacing of sprouting broccoli invites some interplanting. I have tried this with beetroot for salad leaves, even for small beetroot. We had best results with interplants of dill, coriander and parsley, some of which survived through winter. Lettuce and endive could work too.

Broccoli plants, ready to transplant in July after broad beans have finished, with water to prepare the lines for dibbing holes

15th July – I am pushing broccoli into holes dibbed along the pre-watered lines, in otherwise sun-dried soil

Broccoli thriving after being transplanted 10 days earlier, with salad and beetroot popped in at the same time

Late December – this broccoli was interplanted with flat-leaved parsley in July

28th March – the same parsley and broccoli plants have now accelerated; the parsley continued until flowering in May

20th September – interplanted kaibroc between ever vigorous cos lettuce, just picked for the tenth time, each time twisting off the main plant

The same kaibroc on 28th October, now without the lettuce plants; I’ve already had a few harvests from this sowing in late July

Support

The small seedlings we transplant grow uniformly at first. Then, at about six weeks since being planted, they are suddenly quite tall.

2nd July – after broad beans, which cropped in June, we transplanted this broccoli; I am watering the plants which are in dry soil

Nine days after being transplanted, the Claret broccoli stays under mesh for about six weeks

Sometimes after a storm they lean on the ground and look distressed. Fortunately, the growing point and new stem are soon upwards again, and you would hardly know there had been an issue.

Broccoli looking rather windswept after being blown over in late August

Six days later, the broccoli is growing upwards again and looks happy

However, you will have lost some space because when they lean or recline they are in the pathway. I find it simplest to put up with this and brush past, but you could use a stake and string, or string supports, such as those I show for broad beans.

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Transplant size

Transplant time

Plants in summer will encounter many pests, and they are best covered against insects. We use mesh supported on hoops.

Spacing

Calabrese: 30–40 cm/12–16 in
Kaibroc: 30 cm/12 in
Sprouting broccoli: 45–50 cm/18–20 in

Support

The small seedlings we transplant grow uniformly at first. Then, at about six weeks since being planted, they are suddenly quite tall.

Sometimes after a storm they lean on the ground and look distressed. Fortunately, the growing point and new stem are soon upwards again, and you would hardly know there had been an issue.

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Water

How often

Give water every day or two, for the first week after transplanting; thereafter not much unless exceptionally dry. Main watering is as harvest approaches. Also, in very dry weather, summer planted broccoli will benefit from a good dose of water twice a week, for the first two weeks.

Of the most benefit is giving water to summer broccoli when close to harvest, once you see small heads initiating. If it’s hot and dry at that point, water every two days to keep plants growing strongly, with bigger broccoli heads.

6th August – the Marathon plants are now 19 days since transplanting, and being topped up with a little water, at a spacing of 35 cm/14 in; polypropylene bird netting would not stop pigeons who can land on top, but it’s keeping rabbits off plants when young

How much

Brassicas are tolerant of dry conditions, but if you look closely you may notice the leaves are matt rather than shiny, and the colour is slightly more blue rather than bright green. This is not critical, as long plants have an established root system, and are not close to point of harvest. Just a small amount of water can suffice to keep them alive. Then, once harvest time approaches, give a lot of water.

Extra mulch to retain moisture?

This is good in dry climates, and the wide spacings of broccoli allow easy distribution of mulch materials.

Prine and thin

It’s highly worthwhile to remove, regularly, any lower leaves you see, once they start to lose their full colour and turn a little pale or yellow. Also remove leaves that are suffering noticeably from pest damage, which again is normally the older leaves closest to the ground.

Detach leaves from the stems by a downward push on the leaf stalk close to the main stem. This ensures a clean break with no decaying stalk left behind.

The result is:

Good airflow around all leaves at the bottom.
Reduced Alternaria disease, thanks to leaves being drier.
Fewer slugs, because there is less for them to eat, and no decaying leaves for them to hide under at ground level.

Mid-October, after another removal of lower leaves from broccoli, which will overwinter before spring harvests

30th October – Chermayne with lower leaves of broccoli which she has just removed; we put these on the compost heap, but many are edible

December – the lower leaves are still being removed from these impressive stems, and fungi keep appearing in the soil

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Harvest times and methods

How to judge readiness

Broccoli is an assembly of hundreds and thousands of small flower buds. Initially, the buds are tiny and tightly clustered together. Then, in warm weather, they quickly swell and elongate, with buds soon opening to small yellow petals. If this happens, the stem will turn woody and fibrous quite quickly. Plus there may be some decay and yellowing inside the main head.

The largest and most tender harvests are in the middle stage, between tiny buds and flower petals opening. When the temperatures are above 21 °C /70 °F, this gives only a short period of perfect harvest.
If you have many plants and the weather is warm, you can’t eat them all in the short period of perfect development. It’s worth taking some early harvests of slightly immature heads, followed by larger harvests of mature heads.

If possible, as harvest approaches, check your plants every day right at the centre to find the first little broccoli heads, usually when you see new baby leaves curling inwards. At that exciting time, they are clustering over a developing head, as with cauliflowers.

2nd June – a vibrant harvest of calabrese, cabbage, carrots, beetroot, salad leaves and broad beans

4th June – Calabrese Green Magic F1 on the left is growing side shoots after I had cut the main head a week earlier

1st May – a delicious spring harvest with side shoots of purple sprouting broccoli, radish, salad leaves, spring onions, leeks and asparagus

How to pick

The stem of a main head is usually fat and strong, and best cut with a knife in order not to damage the plant. Cut at whatever height you choose, to eat more or less of the stem. Best eating quality will be when the knife slides through easily, meaning there are few woody fibres.

Side shoots are quite different and often easier to snap off. They snap most easily right where they branch off the main stem, but with the lowest part of each stem perhaps being fibrous.

You can also cut or snap them halfway, just above where you see smaller side shoots coming out of that side shoot’s stem. That gives a longer period of harvest, with ever more side shoots of smaller size.

17th April – huge first side shoots of purple sprouting broccoli on this Claret F1 plant

29th October – harvesting this calabrese Pathenon, sown late on 12th July

Calabrese Marathon, sown 18th June and weighing 1 kg/2.2 lb in late September when harvested; this could have been left to grow for a few more days as the buds are still very tight

When and how often

1. Sowings of early spring give a first harvest in early summer, and continue producing side shoots for a month or so, every few days. Probably but not necessarily, it’s worthwhile to remove plants after the first flush of side shoots, for two reasons:

Harvests are decreasing.
There is more time for succession plantings to grow large.

2. Summer sowings for autumn harvest will crop either throughout autumn, depending on the variety, or through late winter and spring. In cool weather, there is less rush to harvest as soon as you see broccoli ready; in winter months, you can pick your moment for harvesting.

Broccoli and beet plants for salad leaves in August, just after removing the mesh cover; we had transplanted them three weeks earlier

The same broccoli on 10th January – still a couple of months away from harvest; fortunately no pigeon attacks yet

With the same bed on 27th March, now sporting some magnificent purple sprouting broccoli heads, and a net against pigeons eating the leaves

Storing

Best temperatures for keeping broccoli for more than a day or two are below 10°C/50°F. In summer warmth, best keep them in the fridge, because harvested heads turn yellow within two days and decay quickly.

Saving seed

This requires a lot of time and space, partly from requiring several large plants. See specialist manuals for how you would manage the process.

Potential problems

Which pests are likely

Flea beetles do the most damage to seedlings and are prolific in the spring and summer.
Cabbage root flies can kill plants by eating their roots, usually in late spring.
Rabbits eat the tender leaves of any plant and are partial to brassica seedlings, which can disappear overnight as a result, leaving only a stem.
Caterpillars arrive by mid-summer and are problematic for about three months after that.
Pigeons can eat so much new leaf that they risk killing plants at any time of year, depending on where you are.

Winter frosts reduce pigeon food elsewhere – the previous morning, 6th January, I found six pigeons among these Claret

We made a structure to keep birds out, using old posts and net, and four hours of time; the posts are mostly 1.8m/6ft fenceposts, with roof battens screwed to them as side rails

Protections needed

Because of pests being so likely, especially on seedlings, I recommend you have some covers ready.

Use fleece in the spring, because that adds warmth at the same time as protecting from whatever pests are around.
Summer plantings need covering with mesh.
After removing mesh from large plants, you could spray them every 18–20 days with Bacillus thuringiensis to protect against caterpillars.
In winter, when insects are hardly a problem, bird netting will probably be necessary because of pigeons.

Calabrese at three months old – it had outgrown its mesh cover by late September and so we removed it

Mid-August – the big moment before removing mesh from month-old broccoli, although the cover could stay on for another month; the main thing is that plants are well established

Purple Sprouting Broccoli Claret F1 under a net cage, with broad bean babies in front

Other likely difficulties, including disease

Club root is the main disease problem, but it’s relatively rare. Spores are most active in warm soil, with less damage to winter brassicas such as spring cabbage, whose growth is mostly in the winter months.

The result of club root infection is formation of galls or swellings, on roots and lower stems. These impede the uptake of nutrients and water.

It is spread in many ways: by the import of infected plants, from infected neighbouring plants, by use of infected tools, by moving infected soil and even from surface water runoff. Spores remain dormant for several years, until coming to life again on host plants.

There are some resistant varieties. However, this is resistance, not immunity, and growth is still somewhat diminished. There is more information on the Simply Seed website.
Club root thrives in slightly acid and wet soils. As with allium white rot, no dig reduces incidence. Also spread just a dusting of lime in spring every year, to lessen the damage.

Alternaria leaf spot (Alternaria brassicae)

This can affect broccoli in the autumn. It occurs mainly after periods of rain, with temperatures around or above about 18° C/64 °F.

You see it as dark circular spots which increase in size, sometimes with concentric rings inside, and a yellow halo outside. It is common on older leaves, especially in less fertile soil.

Regular twisting or breaking off of older broccoli leaves, and removing to the compost heap, is your best control. Use gentle downward pressure on each leaf, even if still mostly green.

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And finally

Clear

Straight after the last harvest, the best clearing method is to get hold of a main stem and keep twisting it, so that the large roots snap off. This leaves a lot of root in the ground which is good. There is some soil disturbance, and it’s worth walking on the uplifted soil to firm it down again.

Cut off all leaves to compost, leaving the woody and fibrous stem, which composts best either sliced or shredded.

Shredders do a lovely job of both chopping and crushing the main stem.
Slicing downwards is far easier than cutting across stem fibres, and even a penknife can manage the downward slice. The intention is to expose more surface area for microbes in the compost heap.

Mid- May – I have just twisted out these stems of overwintered broccoli, before removing leaves and then shredding the woody stems

Broccoli stem pictured mid-shredding – this device has maximum stem diameter of 45 cm/18 in; I needed to split a few of the fattest ones lengthways, so that they could pass through

The result of leaves plus shredded stems of 30 large broccoli plants, now rapidly heating on the compost heap

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Follow with

After final harvests of summer broccoli and early kaibroc, you can transplant beetroot, salads, dwarf beans, carrots and leeks. Once, in July, I transplanted more broccoli after broccoli, and this worked fine.

Spring broccoli finishes in time for almost any succession, including courgettes, celeriac, and climbing beans

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