How do you keep broccoli from bolting?

QUESTION: My broccoli plants bolt very quickly once the temperatures start to rise. How do you keep broccoli from bolting? -Kim R.

ANSWER: Broccoli is a cool weather crop, so when it gets too hot, broccoli plants are quick to bolt, which practically ruins your harvest. Though broccoli that has flowered is still edible, it’s not quite as tasty and it loses nearly all of its nutritional value once it has flowered. Though bolting broccoli plants are a common issue and a problem for even seasoned gardeners, there are a few preventative measures that you can take to help prevent your plants from bolting.

The best thing that you can do to keep broccoli from bolting is to prevent the soil from getting too warm. To keep your soil cool, one proven method is to add a thick layer of mulch to the topsoil around your broccoli plants. The heat will only cause broccoli to flower if it reaches the plant’s root system. A thick layer of mulch will help keep the roots cool, even when the weather starts to heat up. Another way to keep the soil temperatures cool is to water your plants frequently. The cool water can quickly cool down the soil and keep temperatures low until moisture levels dissipate. 

Row covers can be installed to keep direct sunlight from hitting your soil and plants too fiercely. Row covers are often used to keep cool weather crops producing for longer periods, and though they may slow down the maturation process slightly, they can drastically affect the soil temperature and keep your plants from bolting even after the warm weather has become a serious issue.

Another great way to keep your broccoli plants from flowering is to harvest them early and often. As broccoli is a cut and come again vegetable, harvesting the main head will only lead to other, smaller heads to pop up in its place. These side heads will also take a bit longer to bolt, but keep an eye out for opening buds and tiny yellow flowers. If you see a couple of flowers forming in your broccoli heads, harvest the crowns quickly before they flower in full.