How Much Sun Does Broccoli Need? Can It Tolerate Shade?

By Paul Smart •  Updated: 06/03/22 •  6 min read

How Much Sun Does Broccoli Need? Can It Tolerate Shade? Broccoli is one of the most popular winter vegetables that is growing in a garden. As it is a relatively easy plant to grow compared to things like cauliflower many beginner gardeners grow it at home. However, when you are first starting out one of the most common questions asked is how much sun does broccoli need?

Broccoli is a plant that can be grown in either full sun or part shade however the choice of location is largely dependent upon the time of year in which you’re growing the plant. Broccoli is a plant that prefers the cooler parts of the year and in these periods full sun is best. However, when the weather is warmer the yields that can be achieved from the plant are significantly higher when it is shaded according to a study conducted in Thailand.

The study in Thailand showed that using netting to reduce the intensity of the sunlight by around 35% improved the yield of the plant. The study showed that the netting reduced the temperature around the plants from around 97°F (36°C) degrees down to 77°F (25°C).  

The effect that this had upon the plant was that it increased the diameter of the head and by around 10 to 15%. Additionally, it was also shown that the length of time that it took for the head to produce flowers was extended by approximately 5 days which meant that there was more time to harvest the plant at its peak.

These results indicate that when broccoli is grown in optimal conditions that are relatively cool it is advisable to grow the plants in a full sun location as the intensity of the temperature is not too high to negatively affect the plant. However, if you are attempting to grow the broccoli during a period of the year when it is relatively hot there is a significant benefit in protecting the plant from harsh sunlight using shading.

How To Grow Broccoli

Broccoli is a relatively forgiving brassica compared to something like cauliflower as it can be grown in warmer weather provided that you look after it. However, generally, it is recommended that broccoli be grown in the cooler months of the year which means that ideally, you should be sowing plants in early spring and late summer as this will ensure that the plant matures through the cooler parts of the year.

To start the plant off we generally recommend that the seeds are planted into seed trays rather than directly into the garden as it is easier to control the climatic conditions in which the seedlings are grown.  To plant the seeds tart by filling a seed tray with a good quality seed raising mix ensuring that you firm the soil into the individual cells to form solid plugs. This is important as it makes the transplanting of seedlings much easier later on.

In each cell, it is ideal to plant 2 to 3 seeds at a depth of approximately a quarter of an inch to ensure that at least one seedling comes up per cell. If more than one seedling germinates in a cell it is advisable to remove the weakest ones leaving one plant per cell. The seed tray should be stored in a warm location indoors in early spring.

Provided that the conditions are warm enough broccoli seedlings will need to spend approximately 4 to 6 weeks in the seed tray before they are large enough to plant out into the garden. 

Transplanting Broccoli Seedlings Into The Garden

Once the plant is large enough it can be transplanted into the garden, however, even though broccoli is a relatively hardy plant that will tolerate frost ideally the seedlings should not be planted out until the last frost has passed and the weather is beginning to warm up.  

When planting seedlings out in the garden it is best to plant them approximately 12 to 14 inches apart in a location that contains rich moist and free-draining soil with plenty of nutrients. It is also important to ensure that the snail bait is applied around the seedlings to protect them as brassica plants are particularly susceptible to attack from slugs and snails.

How To Care For Broccoli Plants

When growing broccoli plants it is important to ensure that they have an adequate supply of moisture and they are inspected regularly to ensure that there is not a significant attack from pests such as cabbage whitefly. If there are any damaged or dying leaves it is advisable to remove them as they provide an avenue for pests and disease to get into the plant.

With all going well the broccoli plants will start to produce heads after a few months that initially will be quite small however once they reach a diameter of approximately 2 to 3 in it is important to keep a close eye on the plants and ensure that the florets remain tightly packed. If there is any sign of the plants beginning to flower the head should be harvested immediately.

Generally, this will happen much more readily in the spring as the weather is beginning to warm up than in the Autumn when the weather is cooling down. In these conditions, heads can remain on the plant for an extended period of time before you need to pick them.

Once the broccoli heads have been removed from the plant it can be left in the garden to continue to grow as most varieties will continue to produce side shoots that can be harvested a few weeks later. The side shoots are usually significantly smaller than the main head that is removed but if you have enough of them they will make a meal so it is worth keeping the plant around if you have nothing better to plant in the same location.

If you have a glut of broccoli heads it is highly recommended that you freeze them so that you can maintain a continuous supply throughout the year. To freeze the heads the broccoli needs to be blanched for approximately 1 to 2 minutes in boiling water before being drained and packed away. To make it easier to use the frozen broccoli later on it is a good idea to cut the broccoli into the size of that you intend to use in your cooking.

I hope you found this article useful and have great success growing your broccoli at home if you have any additional comments or questions please leave them in the section below.

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Paul Smart