Bolting vegetables (flowering plants) is a common problem
Bolting is when cool season plants start to taste bitter & try to flower and go to seed. This happens because of plant stress from either heat waves or frosts, which signals the plant to reproduce before the end of its life cycle.
Certain plants are more prone to bolting than others.
In general, the plants most susceptible to bolting are cool season crops being grown in warmer weather. Bolting happens easily with spinach, most of the asian crops like bok choi, radishes, certain lettuce varieties, arugula and many mustards with warming or hot spring temperatures.
In the spring the days are warming and getting longer, in the fall shorter and cooler, most cool season crop do better for fall.
The Good & Bad of Vegetable Bolting
Bolting is fine and expected once the summer heat waves set in for cool season crops. Spinach, arugula, mescluns, lettuce, radishes and many others will all eventually bolt, but you often have decent harvests until that happens.
Bolting is bad when you need a full crown of broccoli or cauliflower but the heat stunts them.
Another example is if you didn’t get any spinach leaves or bok choi before they bolted. I’ve found some crops like Chinese cabbage, broccoli, daikon radishes or bok choi to be almost impossible to grow in the springtime before they bolt because the days get hotter. If this is the case for your location consider growing them for your fall garden instead of spring.
I always leave some bolted veggies for the bees as they appreciate the flowers & add beauty.
You can also collect the seeds from bolted plants so long as you’re paying attention to how many plants you have for genetic diversity and you’ve looked into cross pollination between or within plant families.
What it looks like when plants are flowering
In general, a bolting plant will start to create thinner looking leaves if they’re a leafy crop. Most of the leafy greens will start to taste bitter and a central stalk will start growing very tall and that’s where the flowers and seed heads will be. Some crops you can leave to self sow, I often do this with arugula or mache. Others will cross pollinate too easily and won’t result in the same crop.
A bolting cabbage head will start to split open from the center as that is where the flower emerges from. Bolting cauliflower and broccoli will be visible on the head, a cauliflower will not have a tight head, it will start to spread out. Broccoli is a head of tiny flowers before they open, when your broccoli is bolting the head is often stunted and tiny, or large and the flowers will start to open.
Examples of bolting plants
Flowering Bok Choi
How to Prevent Bolting Vegetables
- Grow Bolt-Resistant Varieties: When selecting seeds look for ‘bolt resistant varieties’ meaning these veggies can handle plant stress better. I’m personally an heirloom lover but I’ve learned to that growing hybrids for bolt-resistance. Crops like bok choi, spinach, broccoli and chinese cabbage for example.
- Create Shade: Creating shade for cool season crops before the summer heat sets in is a great way to offer your veggies less direct sunshine. Growing spinach for example under a row of trellised peas or under a teepee of beans are some examples. Many taller vegetables can offer your cool season crops much needed shade and with smart garden planning.
- Lightweight Row Cover: Shade cloth can help block some of the direct sunlight from reaching your cool season crops.
Below you can see shade created for broccoli and lettuce to reduce bolting plants. Tall cosmos flowers and squash vines create shade later in the summer months.
- Practice Succession Sowing: Don’t sow your vegetables all at once, sow new seeds every week or two, so you can increase your harvests regardless of the weather fluctuations. I succession sow cool season crops every week for 6 weeks in the spring and fall. Vegetables that are younger are less likely to bolt than older ones which is why this method works so well.
- Use Season Extenders: to add a couple of weeks to your spring gardening. This provides a longer window to allow the spring greens to grow a good size before the heat wave. Learn more about using hoop tunnels in your garden.
- Varieties: Grow a mix of cool season and bolt-resistant varieties so you have options and variety for changing weather patterns (spring can be unpredictable, some years it’s cool, other years it’s too hot!).
- Soil Health: Make sure your soil nutrients are plentiful and have been restored so that your spring veggies can grow fast before the heat. Increase soil health with microorganisms or learn how to compost