Everyone loves a glorious hot summer day. After all, this type of weather is what we Northern gardeners in the wait for most of the year. Unfortunately, these sudden heat waves aren’t the best weather for many tasty crops. In fact, it can often cause plant bolting, which is downright disappointing for any gardener.
Lots of plants like tomatoes and corn love the hot weather, but many others don’t. Have some of your plants ever shot straight up and produced flowers while you were at work? Or simply when you were away from the garden on a hot day and now you don’t know what to do?
If so, continue reading to learn about what plant bolting is, why it happens, and what you can do about it.
What is Bolting?
So, what is this fascinating process? Well, many leafy greens will go through a process known as bolting. When a plant bolts, it sends up a tall central stem that diverts all its energy into producing flowers, and consequently, seeds.
This behavior is brought on by rising temperatures and longer periods of sunlight. Bolting occurs when the ground temperature rises above 80F and will render your plants inedible in mere hours. The process is known as bolting due to the rapid “runaway” growth that occurs.
Why Does it Happen?
This process usually happens to plants that prefer cooler weather. Once the temperature rises to a certain point, the plant thinks the growing season is ending. As a result, it quickly produces flowers and seeds in an attempt to preserve the next generation.
This is a very dramatic reaction in which your plant may seem fine when you leave for work in the morning, yet will bolt nearly four feet straight up by the time you return home. Since all of the plant’s energy has just been redirected towards producing seeds, the leaves and stems will be tough, woody and often quite bitter.
Plants that are most likely to bolt in hot weather are leafy greens such as spinach, lettuce, and herbs like cilantro. Brassicas like broccoli, Brussels sprouts, kale, and arugula are also prone to bolting.
Note that plants can also bolt when they’re under a fair bit of stress. If you know that you have a plant that’s prone to bolting, make sure you pay close attention its needs. Grow it under optimal conditions and keep it well-fertilized and watered. A plant that’s happy and healthy is less prone to bolting.
What can you do?
You can’t stop a plant from bolting once it’s started, but you can take preventative measures. Make sure that your plants are in locations best suited to keep them from bolting as long as possible. Take notes about your gardening space and plant bolt-prone varieties in the shadiest areas available. If shade isn’t available, create a trellis full of vining plants to create some.
For example, grow cucumbers or zucchini on a leaning trellis over lettuce and spinach. These plants thrive in hot weather, and the leafy greens will thrive in the shade below.
Adjust your growing schedule to take advantage of the cooler months. Since these cool-weather plants can tolerate weather that others can’t, get them going as early as possible. Alternatively, you can also plant them later to harvest in the autumn when everything in your garden is slowing down.
Monitor bolt-prone varieties in order to catch signs of plant bolting early on. If a central stalk begins to form in species such as spinach and lettuce before the warm weather arrives, take action. Cut the plant back to just above the soil in order to allow new leaves to grow in.
Watch the Weather
You can make things easier on yourself if you plan ahead by keeping an eye on the weather. If you know ahead of time that your area is in for a hot spell, you can try to preserve these plants by erecting a sun shade. Old sheets and a couple of garden stakes work nicely for this.
One thing to note when building a sun shade: don’t completely close in the plant. without proper air flow, heat will build up inside the structure. All you want to do is cover from overhead while leaving the sides open to allow for ventilation.
You can also pinch out or cut off any central stalks that you notice forming and quickly cover the plant as noted above. Although it should be noted, if temperatures are already very high, this won’t stop the plant from bolting. It’ll simply give you some time to harvest leafy greens before they become too bitter to be easily edible.
To make the best use of the growing season before bolting occurs, harvest as much as possible and remember to harvest from the outer edges of the plant first. This will promote more growth and result in a larger overall harvest for you.
New bolt-resistant strains of certain plants are being developed all the time. As such, select one of these new varieties when purchasing your next batch of seeds. This will provide you with longer-lasting plants that produce more edible foliage.
What can You Do Once a Plant bolts?
Unfortunately, once your plants have bolted, there isn’t anything you can do to correct the process, or promote more edible growth, but there are a couple of things you can do to salvage what is left of your plants.
1. Extract the Goodness in the Leaves
For plants such as spinach or lettuce, consider adding them into your morning smoothie. If they’re a touch bitter, simply add some fruit to mask the taste. This is a great way to get some extra vitamins.
You may be surprised to learn that broccoli leaves are edible. When dealing with these kinds of brassica leaves—which are much tougher and more fibrous than spinach—juice them to extract their green goodness.
Again, because the plant has redirected its energy into making flowers and seeds, their leaves can be quite tough and bitter. As a result, adding some fruit to your juice will be important. This is especially true if you aren’t used to consuming straight vegetable juice.
Another bolting-prone plant that has surprisingly edible leaves is the Brussels sprout species. You could juice these leaves, but you don’t really need to. They’re not quite as tough as broccoli and are sweeter and milder than collard greens. Instead, consider chopping them into strips and them sautéing them with some olive oil, garlic and some of your favourite seasoning.
2. Harvest the Flowers
Bok Choy, broccoli, and daikon flowers are both edible, and delicious.Try adding them to salads, or juicing them along with any other leaves you harvest. You can also choose to cook them if you like, or you can just snack on them right off the plant.
3. Collect the Seeds
Saving seeds is a wonderful practice that we should all do regularly. After all, each plant will produce far more seeds than you’d ever receive in the small packets purchased from your local produce store or online seed supplier. Once you’ve collected the seeds, use a sieve to remove any debris, and store in an air tight container.
Make sure to label your seeds carefully with the species and date. Then store them in a cool dry place that never gets direct sunlight. In January or February, try doing a seed swap with friends and family. This will allow all of you to expand your garden’s diversity without any monetary investment.
As an added bonus, harvesting seeds from your garden means that the resulting plants will be better suited to your gardening environment. During the growing season, the plants become acclimatized to the specific soil and temperatures in your area. This makes them much more likely to flourish the following year.
If you’re a fan of cilantro and your plants bolt, just wait for the seeds to turn brown. Then, collect some to store, and plant them the following season. Additionally, you can grind some to use in your own cooking. Ground cilantro seeds are actually coriander, so, you’re getting two culinary seasonings for the price of one.
Once you’ve made use of as much of the plants as possible, pull them up and add them to your compost pile. They may not be able to provide you with any more nutrients, but they can go to work creating vital nutrients for the rest of your garden.
The Truth of the Matter
The unfortunate truth is that cool-weather plants will eventually bolt no matter what you do. After all, it’s their nature to do so once the summer days lengthen towards fall. Even though it’s an inevitable process, I hope this article has helped you to see that not all is lost when your plant bolts. Nature is wonderful, and just when you think you’re out of luck, you’ll see that there’s still plenty on offer.