How to Grow Broccoli: Harvesting and Flowering Tips
Growing broccoli is incredibly rewarding, especially when you have looked after it from seed, dealt with pests, and watched the green heads form. If you’re looking for a general overview of growing broccoli, you’ll find that here as well as this post on growing broccoli microgreens.
After planting your seeds or seedlings, tending them, battling aphids, and watching heads form, the next question is: when should you harvest? Should you wait a little longer for a bigger head or are you risking letting it bolt and start flowering?
This post covers growing broccoli, when to harvest, and what to do if it starts to flower.
Recap on How to Grow Broccoli
For a full overview on when, where, and how to grow broccoli, check out this post.
To recap, broccoli prefers the cooler seasons, either in early spring or autumn after the summer heat, but timing depends on your local climate and the number of frost-free days. If your growing season is short you will likely grow partially in the summer season.. But in mid-summer, most varieties will bolt more quickly, and pest pressure tends to increase.
To get a head start into the season you can start seeds indoors, then transplant when the seedlings are about 15 cm tall (4 to 6 weeks after sowing the seeds), once the weather is right. For this it is good to know your approximate last frost date in spring. So that you can have your seedlings ready to transplant when that date comes. Space them 45 cm apart to ensure good airflow. Even in lower temperatures, cabbage moths or white butterfly can still be a problem. They lay eggs on the undersides of leaves in clusters. The best protection is a physical barrier like netting.
When and How to Harvest Broccoli
Broccoli takes about 70 to 90 days to mature, depending on the variety and time of year. Fewer daylight hours can slow growth and delay harvest. In my area I can grow broccoli throughout winter but it will take longer than 90 days because the days are short.
After transplanting the seedling acclimatizes and the stem starts to thicken. The plant should begin producing a lot of foliage. A good leaf growth is essential for the plant to develop a full-sized broccoli head. So don’t be discouraged if you don’t see anything but leaves for a long time.
Once the main head starts to form it won’t be long until harvest.
Head size depends on the variety. Most broccoli will produce one main head of about 15-20cm across. Some varieties, like broccolini, produce several thinner stalks with small florets, instead of one large head.
Flowering Broccoli
The broccoli head it essentially the immature flower of the plant. It bolts due to environmental stress like heat, or delayed harvesting.
Inconsistent watering or lack of nutrients in the soil as well as overcrowding can contribute to bolting. But temperature is usually the biggest factor. Extreme heat or cold can stress the plant leading to early flowering. Watch out for a loosening head and yellowing buds, these are signs that flowering is about to begin.
How to Prevent Broccoli from Bolting
The most important factor is timing. Plant according to your climate, broccoli thrives in cool weather, so check seasonal temperatures. That said, you can’t control the weather, even the right timing can be offset by unforeseen hot or cold temperatures. Mulching will help to regulate soil temperature and keep the roots cool. It will also help to retain moisture. In warmer months, shade cloth can help protect plants from heat stress. The cloths can double as protection from pest.
Most importantly, keep an eye on the broccoli and harvest before it starts to flower. Use the seed packet’s “days to maturity” as a guide but adjust based on your garden’s conditions. If the head is not as firm or starts to separate, it’s time to harvest immediately.
Use a clean knife to cut the stalk at a slight angle, just above the nearest set of leaves. Cutting at an angle helps water run off the stalk and reduces the risk of disease. You can include as much stalk as possible, it’s just as good as the florets.
Harvesting Broccoli
You can still eat flowering broccoli, though the flavor may turn bitter. Its texture also becomes softer, losing the classic broccoli crunch.
Use a clean knife to cut the stalk at a slight angle, just above the nearest set of leaves. Cutting at an angle helps water run off the stalk and reduces the risk of rot or disease. Try to include as much stalk as possible, it’s just as tasty as the florets!
After the Main Broccoli Harvest
Should You Pull the Plant or leave it for Side Shoots?
After harvesting the main head, many broccoli plants produce small side shoots. So even if your main head starts flowering, you might still get a second chance with side shoots. The second harvest might be smaller, it will depend on the variety and overall plant health. Whether you leave the plant or pull it out depends on your growing season and available space. Broccoli plants can grow rather big and take up a lot of room that you might need for another crop that is ready to plant out. So, don’t feel bad if you decide not to wait for those side shoots.
If your broccoli does flower, you’ll be left with a gorgeous yellow bloom. Bees and other pollinators will be glad for the broccoli flowers and make your garden thrive with their presence.
Curious about growing broccoli from seed or how to grow broccoli microgreens?
Check out my full growing guide here or dive into the world of nutrient-packed microgreens. Or check out this post on growing Cauliflower for another member of the brassica family.
