Broccoli has so much going for it. How about the joyous prospect of deliciously tender spears to pick in spring, when there’s little else about? Or the fact it’s contains more vitamins, iron and even protein that most other vegetables? Or maybe just the fact it’s so darn delicious when you grow your own! This is an incredibly rewarding plant if you know how to grow it well. Watch our video or read on to find out everything you need to know to grow a bumper crop of broccoli.
Types of Broccoli
First, a quick overview of the two main types of broccoli. The type shown at the top of the page is commonly just called broccoli, but depending on where you live you may also know it as calabrese. It produces these big, fat, green heads, which are usually picked (at least in my temperate climate) from early summer to early autumn. It isn’t particularly hardy and is best sown in spring.
Then there’s sprouting broccoli. It’s far hardier and typically sown in spring or early summer to give a crop in the cooler months, usually from late winter and on through spring. The spears themselves are more slender and are usually white, cream or – my favourite – purple.
Both types of broccoli are fantastic crops and, if you grow both, should give you a good spread of tasty spears throughout most of the year.
Mid-spring, which is the perfect time to sow a crop of summer broccoli (calabrese). Either sow into pots of all-purpose potting mix, then transplant after germination into their own plug trays, or sow into plug trays – two or three seeds per plug – to then thin out to leave just one seedling per plug. If you have the space and the seed is cheap, then sow into plug trays as it’s no big deal to discard the thinned seedlings.
I prefer to sow into pots. This way, when I start the earliest sowings off (indoors, to get a more even germination), they take up a lot less room. And, to be honest, I rather like the whole transplanting process. It offers such a sense of achievement and it’s proper mindfulness – who doesn’t get lost in the moment on tasks like this?! Plus, you get to choose the best-looking seedlings for growing on.
Broccoli can be sown from as early as late winter – germinated on a warm windowsill indoors – until early summer. Sowing in stages – say once a month – should give a longer harvest and acts as an insurance policy if something eats your first seedlings. Scatter the seeds very thinly over the surface of the potting mix, then cover them with a little bit more potting mix.
I find that all brassicas germinate remarkably quickly and reliably, so expect them to be up within just three or four days. Once they’ve germinated, carefully transplant them into individual plugs or pots, selecting the biggest, strongest seedlings and composting the rest (or you could rinse them off to eat as a tasty microgreen).
I like to transplant the seedlings very soon after they’ve germinated. They are smaller and easier to handle this size, and they don’t seem to notice being transplanted – they’re so resilient.
Sprouting broccoli should be sown in late spring or early summer. That way, they will be ready to go into their final positions when the first crops of the season – salads, peas, garlic, broad beans, and so on – are coming out, so this is a great way to make the most of the space you have by using the broccoli as a follow-on (or succession) crop.
The perfect size for both broccoli and sprouting broccoli is when plants reach about 6in (15cm) tall, usually when they have about two sets of adult leaves. This is typically four to six weeks after sowing, depending on the time of year.
Prepare your soil by adding about an inch (2cm) of compost or manure (or a combination of the two) on top. Grow broccoli in a sunny spot, unless you’re growing in a hot climate, where you may want to offer this cool-season crop a bit of shading. In very hot climates you may need to sow towards the end of summer or in autumn to make the most of those cooler winter months.
Plant your broccoli about 18in (45cm) apart in both directions. You can go a little closer, but you’ll get smaller spears. It’s really up to you how you play it: more plants with smaller spears, or fewer plants with bigger spears.
You can use a dibber to make fairly deep holes then pop your young plants in up to their lowest leaves. You don’t need a special tool to use as a dibber – for instance I often just use the handle on my trowel. Pop the plant in then firm it into position well. Give them a good soaking to settle the soil. And that’s it!
Like other brassicas, broccoli can often be targeted by pests. Early crops of broccoli may escape the attention of caterpillars, as long as they’re harvested by midsummer. But from early summer you’ll need to put up the defenses against caterpillars, as well other insect pests like cabbage aphids and flea beetles.
Insect mesh is light and allows for a good airflow. Nothing can get through it! Support it on some sort of framework - canes with upturned plastic bottles on the top of them is nice and simple, but very effective. This will keep the mesh suspended above the plants so butterflies can’t lay their eggs on the leaves through it, and the bottles protect the mesh from tearing. Make sure the edges are properly secured and flat to the ground (or even buried in the soil) so insects can’t get in from beneath.
You can remove covers later in summer, but then for your sprouting broccoli you’ll need to erect netting to keep the birds (especially pigeons) off your plants. Keep the netting or mesh in place until there’s more natural food for the pigeons to eat, by about midspring. Or just keep the mesh in place throughout the life of the crop, which should also offer plants a bit of protection from the winter weather.
As far as ground care is concerned, keep the soil your broccoli is growing in nice and moist. This will help it grow strongly, making it better able to repel any pests. If you’re in a hot climate, you could also water the leaves to cool plants down on a hot day.
Keep plants weeded, and consider topping up mulches around sprouting broccoli plants towards the end of summer to help. This will give plants more resources to draw on as it gradually gets incorporated into the soil, as well as trapping moisture where it’s needed down at the roots.
Finally, remove any yellowing or damaged leaves. This not only keeps plants looking neater, it also avoids having them rotting, which will only serve to attract slugs.
How to Harvest Broccoli
Harvesting is the best bit – your reward for all that patience and dedication! That said, broccoli may be ready to harvest just two months on from planting.
Harvest summer broccoli while the florets that make up the head are still compact and tight. If they are separating or even starting to open out a bit, you’ve left it a little too late, though they will still be perfectly edible of course! You want to harvest with a bit of stalk, to hold the head together, but don’t cut it too low. Stalks will go on to produce a second bonus crop of smaller heads a week or two later.
Don’t discard the stalks when in the kitchen – they’re some of the best bits and have a slight sweetness about them. I use them in soups – pop them in the freezer and save them up for that purpose. Broccoli’s so good for you – it’s got vitamin C for the immune system, antioxidants, and all sorts of bioactive compounds that help protect against all sorts of ills – so you really don’t want to waste any of it!
Sprouting broccoli won’t be ready till later in winter or spring. Like summer broccoli, harvest the main spear then leave the plants as they are for a second crop of smaller spears to follow. Two harvests for the price of one!
Sprouting broccoli, like many winter crops, actually improves in flavour after a few frosts because the plant converts starches into sugars to help protect it against the cold. To extend the harvest period even further, you can also select varieties of both summer and sprouting broccoli that have different recommended growing dates or times to harvest to give a really long window of harvests. Wonderful!