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Posted by Erica Glasener | Aug 23, 2011

What to do when plants bolt

It's the time of year when your garden plants start bolting. A horticulturists lays out your game plan.

Fennel that has flowered and set seed (bolted).  Photo by Erica Glasener.If you grow vegetables, herbs or flowers, at some point you have probably experienced what happens when your plants “bolt.”   Bolting is defined as “ when plants grow quickly, stop flowering  and  set seeds.”  This term is commonly applied to crops like Lettuce and Spinach but can happen with your flowers too.   Weather can play a factor in bolting.  At the end of the spring when temperatures are consistently rising and then are hot in summer, it’s the natural course of events for cool season crops to quit putting energy into producing foliage and realize that they better produce seed if they want to keep the species going. 

But as a gardener there are some techniques to try that will keep some of your  vegetables and annuals producing over a longer period of time. And, when your plants do finally bolt, there are some things you can do to keep your garden going.  

Herbs: Harvest often

With some plants, like the popular herb Basil, grown for its tasty leaves, the goal is to keep them producing leaves and prevent them from bolting.  The best way to stop them from flowering and setting seed is to harvest the leaves (lots of them and  often).   The more you harvest, the more the plant will produce.     

Some herbs, like Cilantro, will not keep their taste once they bolt.  In this case, let them set seed and you may be rewarded with another crop of fresh plants the following spring. 

Remove developing flowers

Other herbs, such as Parsley and Fennel, will flower and set seed when the weather reaches high temperatures in summer.  Depending on what part of the country you live in, these can behave as perennial, biennial or annual plants. As soon as they begin to flower, cut them back hard (plants may only be 3 to 4” tall) and they should continue to put out more foliage, extending the amount and period of time that they produce. 

Cut back plants and fertilize

Some plants, like the annual Coleus, are grown for their colorful foliage.  To extend their season of interest, cut off any flowers as soon as you see them beginning to form.  You can also cut back plants by 1/3 or ½ to keep them bushy and healthy. 

Regular applications of liquid fertilizer every ten days to two weeks will also help keep your annuals healthy and productive. 

With perennials like garden Phlox (Phlox paniculata), removing spent flowers as soon as you notice them will encourage more blooms and extend the season of interest in your garden. 

Vegetables-replant a second crop

Lettuce, Spinach, Mustard and Kale are all grown for their leaves.  Once they stop producing and bolt in summer, you should pull them out.  A new crop can be  replanted for fall and winter.  With crops like Broccoli, learn to recognize when the heads are ready to harvest, before they begin to flower.  Check with your local Cooperative Extension Service for the ideal time to plant fall crops in your region. 

Once they bolt

At the end of the growing season, if you let plants set seed they may sprout from that seed the following spring.  This is especially true if you don’t disturb the area where they are growing.   Parsley, Fennel, and certain annuals like Impatiens and  Zinnias often reseed. 

Erica Glasener is a Networx - http://www.networx.com - writer.  Read more articles like this one - http://www.networx.com/article/what-to-do-when-plants-bolt - on Networx.com.

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