Top Of The Crops - Broccoli and Calabrese

Broccoli is a delicious vegetable that is a firm favourite in soups, salads, and as a side dish for roasts. Adults and kids alike enjoy eating broccoli (and its less common cousin, calabrese) throughout the entire year.

While most of the broccoli we eat in the UK is imported from warmer climes, it's a brilliant vegetable to grow in your own home garden. There is nothing better than harvesting a head or two of broccoli that you grew yourself, and then roasting it with olive oil, garlic, and freshly cracked black pepper. Delicious!

Have you ever wanted to grow broccoli in your garden, but felt intimidated by the process? Using fruit cages is a handy trick that can help you harvest an abundant amount of fresh, healthy broccoli each and every year.

What is broccoli?

People have been growing and eating brassica vegetables since around the sixth century BCE, and it was a favourite in the Roman Empire. They are still enjoyed and relished today not only for their robust flavour but for their multiple health benefits. Broccoli is packed with vitamin C, A, E, and K, as well as selenium, iron, calcium, and magnesium. It's also a great source of fibre and protein.

Broccoli can have a pungent smell and taste due to its high levels of sulphur-containing glucosinolate compounds, such as isothiocyanates and sulforaphane. If you enjoy this taste, lightly steam, stir fry, or blanch your broccoli. However, if you find the taste a bit too strong, try roasting it in the oven, or boiling it for longer.

While you might assume that rapini, also known as broccoli raab, is a type of broccoli, it is actually a type of turnip!

What is Calabrese?

Calabrese is also known as Italian, American, or green sprouting broccoli. It forms a taller plant than broccoli (up to 2 feet, or 60 cm tall), and has bluish-green heads 15 cm in diameter. Not a fan of broccoli's bold flavour? You might prefer calabrese, as it has a milder flavour. It is also regarded by the Royal Horticultural Society as an easier crop to grow, so give it a try in your garden!

Growing Broccoli and Calabrese in Polytunnels

Polytunnels make it easy to grow brassicas no matter what the weather outside. Sure, you can grow broccoli and calabrese outdoors in your garden, but with a polytunnel, you can better control the growing temperature and prevent pests from getting at your crops. Slugs, snails, and birds can all be deflected with a polytunnel.

Some gardeners have a lot of success sowing their broccoli in a polytunnel and growing it to a juvenile stage before then transplanting it to an outdoor space.

How To Grow Broccoli and Calabrese

It is best to sow your broccoli and calabrese seeds between February and June. Place two seeds per cell, and then place the cell tray in a warm greenhouse space or polytunnel until April, at which point you can place them outside. Once your seedlings poke through, choose the more robust of the two and thin down to one plant.

Prepare your soil by adding general purpose fertiliser at a ratio of 150g per square metre. Once the plants have an established and well-bound root ball, plant them outside your garden in full sun. They will also do well in very light shade. Maintain at least 30cm (12in) between each plant, and at least 45cm (18in) between the rows. If you want to limit the side shoots, space them closer together.

If you want to plant broccoli or calabrese seeds directly outside, sow three seeds in holes 2cm deep, in a row every 30cm (12in) along. When your seedlings are large enough to handle, thin them down to leave the healthiest of the three. In April, cover your seedlings with fleece to prevent the cabbage root fly from ruining your crops, removing by mid-May.

Water your broccoli crops every 10-14 days. Once your plants are 20cm (8in) tall, add a weekly high nitrogen fertiliser at a ratio of 35g (1oz) per square metre/yard. If the weather is particularly hot that summer, the plants might go to seed too early they tend to do better in cooler summers.

Consider companion planting for the best results. Basil, thyme, onions, and garlic will all repel common pests like slugs and snails. Lettuce can be planted between the rows and harvested before your broccoli spreads and needs more room. Legumes can add much-needed nitrogen into the soil.

How to Harvest Broccoli and Calabrese

Your calabrese and broccoli will likely be ready to harvest between July and August. You'll know that they are ready to harvest when the edible heads and stems are a good size, but before the buds begin to flower.

When you harvest your first heads of broccoli, leave the plant alone, and secondary heads will start to fill in the gaps. Your sprouting broccoli will overwinter, the perennial variety will last around five years for a lovely and delicious low-maintenance crop.

When you want to harvest your broccoli, take a nice sharp knife and cut the stem approximately 10 cm below the head with a clean cut. Don't saw at the stem, as you could damage the plant and prevent secondary heads from developing. After this initial harvest, your plant will yield smaller head shoots, which you can cut and harvest in the same way.


When should you harvest and sow broccoli and calabrese?


Most broccoli and calabrese is ready to harvest in July and August. Knowing when to harvest your broccoli can be a little bit tricky, but there are a few simple signs that will tell you that it is time.

  1. It has a head Broccoli needs to have an initial head before it can be harvested the head should be tight and firm to the touch.
  2. Head size - The best time to harvest your broccoli is when the head is between 4 to 7 inches (10 to 18 cm) wide. While size provides a good guide, the other signs should be assessed before you harvest.
  3. Colour - Broccoli and calabrese should be a vivid deep green. When it starts to turn even the slightest bit yellow, thats a sign that the florets are going to seed harvest immediately if you see this.
  4. Floret size - Check out the size of your florets. The florets should be the size of a matchhead before you harvest them.


Sow your broccoli and calabrese in the spring after the final frost if planting outdoors, or in late winter if using a polytunnel or planting in seed pods inside. Don't ever plant them outdoors until you can be sure that the final frost has passed, as this will kill your crop.


Following these tips will help you harvest a bountiful crop of broccoli and calabrese. Broccoli is a delicious and healthy crop that is easier to grow than you might think. Use the guide above to get fresh and tasty broccoli and calabrese on your table next summer and beyond.

Reference List

  • Rhoades, H. (2019). How to Harvest Broccoli. [online] Available at: [Accessed 20 Jul. 2020].
  • Royal Horticultural Society (2019). Growing your own - calabrese / RHS Gardening. [online] Available at:
  • Calabrese#:~:text=Calabrese%20is%20a%20fast%2Dgrowing [Accessed 20 Jul. 2020].
  • Wikipedia Contributors (2019). Broccoli. [online] Wikipedia. Available at: [Accessed 20 Jul. 2020].