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Sow it. Grow it. Love it! Calabrese (Broccoli) - growing diary

Our calabrese growing diary is designed to help if you are looking to grow broccoli for the first time, or maybe you are just looking for some tips on how others grow them on the West coast of Scotland.

After years of growing calabrese in the summer and being plagued with having to share the results with caterpillars, not to mention all the fleece and other barriers to keep the egg laying butterflies at bay, I reverted to a different strategy. This has the advantage of producing 2 crops of calabrese. One at the end of June and a second in October. It is also reasonably butterfly friendly in so much that they get to nibble the leaves and I get to eat caterpillar free calabrese. The only disadvantage when compared to successional sowing is that it produces two gluts of the crop. However, this can be to the gain of our neighbours.


In early March I sow about 10 seeds in multipurpose compost with sharp sand. This is enough as the plants take up rather a lot of space in the garden. These are sown in a small container in a cold greenhouse or cold frame. To aid germination I cover the pot with a small piece glass, but clear plastic from packaging would also work

Calabrese normally germinates in a few days and when the seedlings are about 3cm tall I pot them on into small pots about 4cm wide, keeping them under cover. The photo shows the plants at the stage where they are ready to be transplanted.


The seedlings will grow quickly and I pot on into larger pots such as 500ml yoghurt pots that are about 12cm deep. I do this when the roots are escaping from the bottom of the smaller pots. At this stage I keep the plants under cover to promote fast growth. When the roots start to emerge from the larger pots I begin the hardening off process by putting the plants outside during the day:


Once the plants are hardened off and are at least 10cm tall it is time to plant them out.

This could take place at the near the end of April, just depends on the weather forecast (frosts and gales) and making sure you have hardened off the plants for a few days.

Keeping plants in pots, I lay out the pots in the area I have available. Brassicas grow quite large and it is always a temptation to plant too close together, but then again most of us don’t have a massive area available and it is a balancing act.

I leave about 60cm between plants. Before planting, I place pots on soil and move about till spacing is about right. Much better to do it this way than planting and realizing half way through spacing isn’t going to work well.

I dig a small hole slightly larger than the pot, about 20 cm deep, and throw in a small handful of lime. This is to guard against disease such as clubroot which tends to develop in acidic soils that we have in Helensburgh.

I mix the lime in with the soil a bit then knock the plant out of the pot and plant in the soil. The roots in the pot should be developed enough to hold together the soil from the pot

The soil is filled in around the plant. The soil will be touching the first set of leaves. Brassicas generally live to be planted quite deep. Then firm in well.

This is important because the plant will grow to about 60 cm tall and the roots need a firm soil to support the plant. This is important here on west coast as it can be windy and it isn’t unusual for plants to get blown over.

Plants all planted and watered in.

Not many butterflies about yet - so no caterpillar worries. My only concern is the family of pigeons that are lurking about. If they start getting too interested, then may need to protect the plants, but for now, see what happens. I have kept a couple of plants back as an insurance policy just in case of any failures or damage.


If weather is dry water the plants. The plants will grow rapidly and by the end of the month will be starting to form the large edible flower heads. If you start to see any signs of the flower heads turning yellow, the heads must be picked immediately. Ideally pick a few days before this stage.

At the end of June it is time to start to repeat the process by planting seeds. This time around, they do not need to be in a greenhouse. I plant in a small pot or container as before, but often put the pot in a shady place to germinate.


The large heads from the first sowing will now be harvested and smaller side shoots produced.

The seedlings will need transplanting and can be kept outside in a sheltered spot. They don’t need too much sun at this stage. If there is really heavy rain, it may be an idea to provide some shelter.

At this stage the butterflies should be around in abundance, and as far as I am concerned they can lay eggs on the old plants and the caterpillars can have a good munch on the leaves. However, I am not too happy about them munching the new plants. These will need to be checked every couple of days and any eggs or baby caterpillars picked off. Some damage is inevitable, but it will only be affecting the leaves and not the crop.

Towards the end of July the original crop can be dug up and composted. If you notice that the roots are a bit twisted, swollen or deformed, then these should not be composted as it is sign of club root that sometimes affects the brassica family.


By early August I hope to be planting out the second sowing as soon as the plants are about 10cm high. Planting takes place in spaces between where the first crop was planted. Again butterflies will be a bit of a problem, but checking every few days to remove any baby caterpillars usually keeps damage to acceptable levels. Most leaves will have some damage, but as long as the plant carries on growing it doesn’t matter.


The rate of growth will slow down, but usually by the end of the month the flower heads will have formed. Most importantly butterfly activity will have receded by the time the heads start to grow.


The heads will gradually grow to a size when they can be harvested and be caterpillar free.


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