No More Bolting! Your Guide to Broccoli Plant Perfection (2024)

VEGETABLES > BROCCOLI > BOLTING

By ELIZABETH WADDINGTON

Broccoli is still edible once it has bolted, but it can be disappointing if it occurs early and you have not obtained a worthwhile yield from your crop.

Broccoli plants can be prone to bolting (running prematurely to flower and set seed) when the environmental conditions are not right.

Most commonly, broccoli and Calabrese will be most likely to bolt due to stress caused by temperatures (most commonly too high but also potentially too low early in the growing season), water shortage, or a lack of nutrition.¹Bolting in vegetables. (n.d.). Royal Horticultural Society. Retrieved March 13, 2023, from https://www.rhs.org.uk/vegetables/bolting

Sometimes, extreme weather conditions may be to blame for the bolting – and environmental factors may be largely out of your control.

However, a lot of the time, the decisions you make and what you do as a gardener can be to blame.

Once a plant has bolted, you can slow it down, but unfortunately can’t bring it back.

However, taking steps to prevent your crops from bolting in the first place can often help you avoid disappointment – and making changes can help you grow broccoli more successfully in future if this is a problem that you have encountered more than once in your garden.

So, to reduce the chances of bolting broccoli plants, here are a few tips:

1) Choose The Right Location

Choosing the right spot for growing broccoli can help you avoid many of the common issues – bolting included.

Remember that bolting is caused by stress of some kind, which encourages the plants to rush to reproduce.

Plants that are placed in a suitable location with good, fertile soil (or growing medium) and optimal conditions in terms of sunlight and temperatures are far less likely to have a problem.

Broccoli likes a situation in full sun or very light shade, with a fertile, and moisture retentive yet well-drained soil.

In very hot summers – especially in the south – a lightly shaded spot may be preferable, since broccoli forms better heads in cooler summers here in the UK.

In a very hot location, when temperatures rise too high, broccoli is far more likely to bolt.

2) Sow & Plant At The Right Time

When exactly you sow your broccoli will depend on which type and variety you are growing and where you are growing it.

Typically, seeds can be sown between March and June or July.

Seeds are sown indoors or under cover in seed trays or pots before the last frost date, and can be direct sown, usually, from some time in April onwards.

Sowing earlier can sometimes be a good policy for summer-harvested heading broccoli (Calabrese) since you can harvest before the weather heats up too much.

However, sowing too early can sometimes be problematic too, since plants can bolt if they are not potted up or planted out in time and the roots become too confined or starved of nutrients in their containers.

If indoors grown plants are placed outside too early, or placed out without hardening off, they may be stressed and may bolt due to a cold snap or too extreme a change in temperatures and conditions.

So make sure you are aware of the temperature expectations where you live, and keep an eye on weather forecasts before you decide to plant your broccoli outdoors.

3) Practice Companion Planting & Crop Rotation

Generally, the healthier and happier your broccoli plants are, the less likely they are to experience the stress that can lead to bolting.

Like us, broccoli plants will be happiest when they have good neighbours.

So make sure you think about companion planting, which can improve environmental conditions, reduce pest problems, and help maintain a balanced and fertile growing area.

Practising crop rotation with brassicas like broccoli can also help make sure that the soil remains healthy and the plants are less likely to succumb to diseases or be stressed in other ways which cause them to bolt.

4) Mulch Plants To Keep Soil Cool

Another important strategy to maintain the fertility of your growing areas and meet broccoli’s higher nitrogen needs is to mulch well around your plants with a nitrogen-rich organic mulch material.

A mulch won’t only help maintain fertility and a healthy soil, it will also help reduce competition for the broccoli from weeds that might pop up.

Crucially, it can also help keep the soil cool.

Broccoli does not typically bolt due to high air temperatures, but rather due to high temperatures of the soil.

Keeping the soil cool with an insulating blanket of mulch will help stop roots from overheating during warm summer weather.

A good mulch should also help keep conditions moist, and reduce the amount of water that is lost through evaporation from the soil surface around your broccoli plants.

This should help reduce issues caused by drought, which can be another common cause of bolting.

5) Water Broccoli Plants Correctly

Of course, in addition to taking steps to conserve water in the soil, it is also important to make sure that you water your plants sufficiently, especially during the summer months.

Broccoli is quite a thirsty plant. Typically, you will need to water outdoors grown plants every 10-14 days in dry weather – more frequently of course if you are growing broccoli under cover, or in containers.

When watering, make sure that you water plants at the base, rather than from above, to use water more efficiently and make sure that it gets where it needs to go – into the soil around plant roots.

If you have a larger garden, or struggle to maintain your watering routine, consider adding drip irrigation, and perhaps an automated system, to make things easier.

6) Harvest Promptly

While plants will sometimes bolt prematurely, it is also important to remember that broccoli can also begin to flower and go to seed if you simply leave it too long before you harvest your crop.

Keep on top of harvesting and harvest promptly to make sure you make the most of your produce and do not miss out.

7) Choose Bolt-Resistant Varieties

Finally, if you consistently experience problems with broccoli bolting in spite of your best efforts, you might like to consider trying to grow more bolt-resistant varieties next year.

Some broccoli cultivars are less prone to bolting than others.

Hybrid F1 seeds often have better resistance to bolting and handle stress better, though you should note that these will not come true from seed like heritage varieties.

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  Bolting in vegetables. (n.d.). Royal Horticultural Society. Retrieved March 13, 2023, from https://www.rhs.org.uk/vegetables/bolting