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The Garden Decoder: What Happens When Edible Plants ‘Bolt’?

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The Garden Decoder: What Happens When Edible Plants ‘Bolt’?

September 27, 2018

I once had a vegetable garden. It was small and cute (roughly four by six feet), slightly raised, and enclosed by four thin planks of wood. The best part? It had come with the house, and presumably all that needed to be done was plant seeds and, as they say, just add water. I did till the ground before I planted. That much I knew. I only wish I had known more.

That spring, I planted carrots, cucumbers, green beans, rosemary, kale, and bok choy. It was the bok choy that I looked forward to the most. Growing up in a Chinese-American household, I ate the vegetable at least weekly; I wanted to make it a staple for my kids too.

One day, I checked in on my fledgling garden and discovered little yellow flowers sprouting from the tops of the bok choy. Cute, I thought. A week later, they towered over the leaves, which were still in their infancy. I called my mom, who, as usual, was full of bad news. “It’s too late. You can’t eat them now,” she said. I rolled my eyes. I Googled. And I discovered my mom hadn’t exaggerated after all. My bok choy—and my kale, too, as it turned out—had bolted.

What happens when an edible plant bolts?

Bolted bok choy. Photograph by Jade Craven via Flickr.
Above: Bolted bok choy. Photograph by Jade Craven via Flickr.

When a vegetable or herb bolts, it has prematurely gone to seed and is now spending more of its energy growing the flowers and seeds than the leaves (leaves are what you want from edible plants). Bolting produces plants that are tough, woody, and bitter—basically inedible. The edibles that are most at risk of bolting tend to be leafy crops that thrive in cooler temperatures (see last week’s The Garden Decoder: What Is a ‘Cool-Season Crop’?). Why? Read on.

What causes bolting?

 Cilantro is an example of an herb that&#8
Above: Cilantro is an example of an herb that’s quick to bolt in hot temperatures; it grows best before and after summer. Photograph by Marie Viljoen, from The New Vegetable Garden: 7 Essentials to Grow (and Eat) in Autumn.

Hot weather and longer days are the biggest culprits—which explains why cool-season crops are likeliest to bolt. When temperatures rise above 70 degrees Fahrenheit and there’s prolonged daylight, these plants go into survival mode and quickly switch their focus to producing seeds.

Bolted kale. Photograph by Keith Rowley via Flickr.
Above: Bolted kale. Photograph by Keith Rowley via Flickr.

Not surprisingly, bok choy and kale are cool-season crops; I had planted my garden in the middle of spring—closer to summer than winter—and not early spring, as recommended by gardening guides and my more gardening-savvy friend, who, when I told her my plans, politely remarked, “Oh, they usually do well in colder weather, but I’m sure they’ll be fine!” (Note to friend: Next time, tell me when I’m doing something dumb.)

How do you prevent bolting?

See more of this edible garden at Walled Gardens: An Organic and Picturesque Plot at Old-Lands in Wales. Photograph by Britt Willoughby Dyer.
Above: See more of this edible garden at Walled Gardens: An Organic and Picturesque Plot at Old-Lands in Wales. Photograph by Britt Willoughby Dyer.

For cool-season crops, time your planting for either early spring or late summer/early fall, so vegetables can mature in cool weather. You also can try to keep the soil temperature down by topping it with mulch and watering regularly. If you insist on growing cold-loving crops, such as lettuce, in the summer (it’s salad season, after all), plant them where there’s some shade. Also, you can discourage bolting if you continually harvest (pick the outside leaves) and trim seed shoots if you see them. Last, consider choosing varieties that aren’t predisposed to bolt; they’re often marketed as “slow-to-bolt” seeds.

New to gardening? See our curated guide to Edible Gardens: A Field Guide to Planting, Care & Design and  our guide to Drip Irrigation 101. Be sure to check out:

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