Bolting is the event when a plant sets to flowering and starts going to seed early due to heat/sun exposure. It is the plant's last-ditch effort to preserve itself before it dies, most commonly occurring with annuals. Instead of attempting to survive amid the heat, the plant puts its energy into producing seed to ensure its longevity. New leaf growth ceases and flowers rapidly appear.
There are a few different causes of bolting. Simply put, the plant is stressed, which initiates bolting. The stress is a result of heat-related issues:
Some varieties suited for early spring planting can bolt as the day lengthens over the course of the season. The longer the day, the more sun exposure the plant receives. An over abundance of sun affect broccoli, cabbage, leafy greens, onions, peas, and herbs.
During an unexpectedly hot spring, soil temperatures can rise rapidly. If this happens early in the plant's lifecycle, bolting will surely occur. Most spring and summer garden vegetables are well-equipped to deal with warmer soils later in its lifecycle, but as a tender adolescent, the heat stress will begin the bolting process. Soil temperatures can also rise rapidly if the plant is not watered adequately. During a spring like this, watch your root veggies, squash, and cucumber plants closely.
Keeping the roots happy is essential to preventing bolting. Roots can become stressed if disturbed during the transplanting process, or if your plant's root system does not have enough room, such as being transplanted into a container that is not large enough to support it. Poor soils can cause bolting too.
Here are the ways that we recommend to avoid bolting:
- Opt for seed varieties that are bolt resistant.
- Plant at the ideal time for the seed and the season.
- Plant in an area with blotted shade.
- Try direct sowing your seeds to prevent root disturbance when transplanting.
- Water regularly—and in the morning.
- Provide a layer of mulch for your seeds to keep soil cool and protected.
What if your plant is already bolting? Is there anything you can do?
Unfortunately, there isn't a whole lot that can be done. Sure, you can trim back the bolting sections, but the damage is already done. The flavor is greatly diminished after bolting, never to return. However, parsley and basil have a chance if you trim the bolting sections early enough and begin providing it with shade and cooler soils.
Keep in mind that if bolting is left untreated, your plant will go to seed and (depending on the species and variety) could return the next season.