Basil Plants Bolting | Why it happens + How to stop it

Basil plants will bolt when the weather cools off, when the plant matures and it grows tall. A flower will form on the end of the plant and the basil will go to seed. This will turn the leaves bitter and the stems will become woody. Prevent basil from bolting by planting it in spring and summer and pruning it regularly.

Supermarket basil can often bolt rapidly after planting in fall and winter. Basil will be grown out of season in greenhouses and shipped to supermarkets to be used easily in cooking. These plants can be tempting to plant out in winter but the cold weather can cause the plant to bolt.

This article will explore why basil plants bolt and how you can stop this from happening.

Why basil plants bolt

Basil plants will form flowers and seed pots when the plant is left untrimmed or if the weather turns cold. At the end of the summer season when the temperature cools in fall the basil plant will be getting ready to reproduce for the next season.

The basil plant will lengthen, growing tall and reaching up high. The flowers will form on the end of the stems and if left there they will be pollinated by passing bees or flies. These flowers will then form small seed pods on the end of the basil plant.

When a basil plant bolts, growing flowers and setting seed the leaves will turn bitter. The plant will focus its energy on the flower and seed growth and will stop growing new leaves. The stem will harden going woody and holding the seed pod up.

If left on the seed swill dry and drop to the ground. These can be collected in a paper bag and replanted the next year.

How to stop basil plants from bolting

Here are my top tips for preventing your basil plant from bolting. This will keep it growing lots of leaves for your recipes and stop the flower and seed pots from forming on the end of the plant.

Prune regularly

Pruning is the key to stopping your basil plant from bolting during the spring and summer season. A basil plant that is left untrimmed will grow a long, tall stem and eventually a flower head on the end of the plant.

Pruning the plant by trimming off the top 1-2 inches off. Remove the top 4 leaves of the plant by pinching it off with your fingertips, trimming with kitchen scissors or using sharp secateurs. When harvesting large amounts, remove the top 1/3 of the plant to encourage it to branch out and grow new stems and leaves.

Regularly trimming basil, even as often as every 2 weeks during summer will prevent the plant from bolting, reaching up, growing flowers and setting seed. This will give you lots of tender and sweet basil leaves for many months.

Plant basil in spring and summer

Planting basil in spring and summer is a great way to prevent bolting. A mature plant will be triggered to grow flowers in the cooler weather of fall and winter. Plant new basil seedlings out in spring and summer instead and it will spend more time growing leaves and stems instead of bolting.

Basil plants can be available all year round even from supermarkets. Growing these out of season in the winter months can be done in a greenhouse but is trickier in cooler climates. I live in a sub-tropical area and my basil planted out in winter still bolted quickly even though the winter weather was mild.

Light liquid feed of nitrogen fertilizer

Feeding basil regularly with a liquid nitrogen fertilizer is key to encouraging more leaf growth and will delay bolting. Liquid nitrogen fertilizer will benefit basil by keeping it moist and adding extra nitrogen to encourage leaf growth, chlorophyll formation and new stems.

I like to use a light nitrogen fertilizer like fish emulsion. This is a natural substance that will also work to feed soil bacteria which will help to break down and release nitrogen from the organic matter in the soil.

Slow release nitrogen fertilizer like pelleted chicken manure can be placed on the plant at the time of planting and again 4 weeks later.

These are my top ways to prevent basil plants from bolting and instead keep producing soft, tender green leaves.

Can you eat basil after it bolts?

You can eat basil after it bolts but the leaves may be tougher, taste slightly more bitter and the stems may have hardened. The plant will be focusing its energy on growing flowers and setting seed instead of leaf growth. The plant will be changing its chemical production to focus on seed growth and the taste will change.

While you can still eat basil leaves after it bolts but it will have a different flavor. Using them in cooked dishes might be a great idea and save the young new leaves to eat fresh.

What to do with basil that has bolted?

Basil that has bolted can be left to form seed. The flowers can attract pollinating insects to other fruiting plants in your garden. The seeds can be left to dry out and collected in a paper bag. Trim off the seed heads and place them in a brown paper bag to dry out for 2-3 weeks. Shake the bag and the tiny seeds should shake free of the flower head.

Basil Plants Bolting | Summary

Basil plants will bolt growing flowers on the end of long stems and eventually forming seed. This can be prevented by trimming the basil plant regularly over spring and summer. Plant basil in spring to give it time to grow lots of leaves.

When you trim off the stems, the plant will grow back new tender stems to replace the old ones. This will keep the plant smaller and bushier with small, tender leaves.

Happy planting