How To Keep Your Plants from Bolting

July 22, 2016July 12, 2016

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Do your plants bolt before you have a chance to harvest? Try these tips to minimize the problem.

Nothing is more frustrating as a gardener than nursing your crops along through the cool spring weather, only to have them bolt immediately as soon as hot weather hits!

Bolting (when a plant puts up flower stalks to go to seed before the crop has matured) can occur for a couple of different reasons, but most are related to temperatures and weather conditions. Some plants bolt in response to hot weather, others after a cold snap. Others respond to changes in day length. And some are triggered by drought or other stressors.

While weather conditions and day length aren’t something you can really control, there are a few things you can do to minimize the chances of your plants bolting before you are ready to harvest.

If you have problems with bolting, here are a few tips to keep in mind:

1.) Plant bolt-resistant varieties: Some varieties, for instance ‘Boltardy’ beets, are specifically bred to be resistant to bolting – so this is a logical place to start! Use bolt-resistant varieties for the earliest sowings of annual vegetables that respond to increasing day length: spinach, lettuce, beets, arugula etc. Resistant varieties are also a good option for biennials like onions and carrots that are sown very late in winter/early in spring. Onion lovers should also seek out heat-treated onion sets, which are exposed to high temperature, a process that dramatically impedes flower bud formation.
2.) Time sowings: Biennial vegetables sensitive to cold snaps can also be started off within a greenhouse before planting out under cloches once the weather has improved. For annual vegetables, don’t forget to sow little and often to ensure a steady supply of quick-growers such as lettuces – this way you can pick leaves in good time, before they become too old and more likely to bolt. Oriental leaves such as bok choy and mustards are best sown a couple of weeks after the summer solstice, once day lengths are visibly beginning to shorten.
3.) Shade cool-season crops: Relentlessly hot, dry summers are rare where I live – for me it’s more about maximizing light levels and willing plants such as tomatoes to produce their fruits before the nights turn cold! But if you are growing in a hot part of the world then offering shade for cool-season crops is a must. Grow the likes of lettuce and spinach in the shadow of taller plants such as pole beans or corn. Shade cloth can also be deployed and makes a dramatic difference to plants that would otherwise wither and collapse in full view of the sun.
4.) Maximize soil health: Healthy soil with plenty of nutrients and balanced moisture levels will, of course, encourage the quickest growth. Every gardener should aim for this ideal, but particularly those growing in hotter climates where there’s a race to get in leafier salads and vegetables before the hottest months hamper progress. Or simply wait until the weather cools off a little in late summer. Target your watering to those plants that need it most. Cool-season crops will benefit from moist soil the most, while dry soil also plays havoc with brassicas such as cauliflower and arugula.