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Keeping Your Herbs from Getting Leggy

Leggy herbs and preventing them from becoming leggy.

Keeping an indoor herb garden is a great way to bring the outdoors indoors and grow tasty food items for your table. Whether you want handfuls of basil to top your weekly pasta dinner or fresh thyme to sprinkle on a roasting chicken before you bake it, growing herbs is fun, fairly simple, and takes just a few minutes per week.

One common problem that many indoor herb gardeners may have is when their herbs get leggy. However, when you know what you are doing, you can easily avoid this common problem.

What Causes Leggy Herbs?

Different types of leggy herbs in pot.

If you are new to gardening, you may be unfamiliar with this terminology. When experienced gardeners talk about leggy plants, what they mean is that the plant is growing in an unhealthy way. Instead of sturdy, upright stems, the stems of a leggy plant are flimsy and floppy.

The plants will have a spindly appearance and fall over very easily.  When your herb plants get leggy, a strong breeze or a slight bump may lead to broken stems and plants that are destroyed.

Insufficient light is often to blame for leggy herbs. Often you might find floppy, leggy growth on plants that you brought home from the store. Sometimes these plants suffer from insufficient lighting levels in the store and they start growing poorly. Other times, if you are growing herbs from seeds, they may not have enough light and they will grow spindly.

If you have set your herb pots outside for the summer and later bring them indoors for the winter, the plant may send out new scraggly looking shoots as it adjusts to the lower light levels indoors. Rosemary is commonly afflicted with this problem when you take it inside to avoid the chilly temperatures of fall weather. 

Another reason for leggy growth is insufficient pruning. Pruning snips off existing stems, which stimulates the plant to produce new leafy growth. When you prune, plants that are too tall and scraggly will begin to grow rejuvenated, full, and bushy. 

Pruning to Prevent Leggy Herbs

Man's hand pruning rosemary plants.

Regular pruning is part of keeping your herb plants healthy. New plant owners may be aghast at the thought of cutting off pieces of their beloved plant “babies”. Don’t worry! This is a natural part of the life cycle of growing herbs. 

Pruning herbs is just a simple process of snipping off leaves and stems of the plant. It isn’t very complicated and you can use the snipped pieces of the plant in the kitchen. 

You can prune your plants with a small, sharp pair of scissors. If you have diseased plants, you should clean your herb cutting scissors with a soft cloth soaked in white vinegar to disinfect the blades. This will prevent the infection of your healthy plants with the disease.

You can also prune your herbs with your fingers by pinching the stems with your fingers. You should always break the stems cleanly and try to avoid stretching the stems or creating rough, jagged, or shredded stems where diseases can take hold.

Pruning Herbaceous Herbs

Gardener pruning leggy basil plant in pot.

Herbaceous plants are a class of annual herbs like chives, basil, and mint. These plants are tender, and they are fairly easy to prune. Just take out a pair of scissors and snip them. One hint to keep your plant growing full and lush is to cut the ends of the stems, leaving the lower leaves to grow bushy.

For instance, when you are growing basil, you will want to trim the young plant by cutting back the ends of the stems and leaving the bottom leaves to nourish the plant. You should do this when the plants are several inches tall. 

Just remove one or two inches of growth at the end of each stem when you prune herbaceous herbs. The pruning will stimulate two or three new stems to sprout from the spot where you cut the pieces, creating extra branches on your plant. When you grow herbaceous herbs, you will need to prune every few weeks to keep the plants from getting leggy. 

Besides keeping your herbs from getting leggy, pruning will also keep your tender herbs from getting bitter after flowering. Tender herbs will start to die after they produce flowers. Additionally, the leaves will grow bitter after flowering. To prevent this natural cycle, just cut back tender herbs before they flower and the plant will last for months, producing lots of delicious leaves for your kitchen.

Pruning Evergreen Herbs

A woman pruning rosemary plants in garden.

Evergreen herbs stay green all year round, and plants like rosemary, sage, and thyme are included in this group. These types of herbs need to be pruned about once a year, in either the spring or in the fall. If you don’t prune these plants, they will grow woody and the new growth will get spindly.

To prune these evergreen herbs, lightly clip the new growth in the spring. The plant will put out fresh growth that is bushy and full and this new growth will have more flavor than the older bits.

The key to properly pruning your herbs is to never cut the plant back to more than one third of its total size. You should never cut the plant back completely. For your herb plants to do well, you have to leave enough leaves for the plant to create energy to sustain itself. When you prune, your plants will generate new fresh growth with superior flavor. 

Increasing Light Levels to Prevent Leggy Herbs

Herb plants in pot.

Besides a lack of pruning, one other major reason for leggy herbs is a lack of sunlight. This happens frequently with young plants that are reaching for as much sunlight as possible. The tiny plants grow overly long, thin, and weak stems. Beginning gardeners often think that tall plants are a good thing, but actually, when you are growing herbs, you want them to grow slowly and bushily. 

Most of the classic herbs need plenty of sunlight to grow well. Rosemary, lavender, basil, oregano, chives, mint and sage are all herbs that are considered “full sun.” This means that they need at least 6 to 8 hours of direct sunlight per day.

If you live in the Northern Hemisphere and you are growing a windowsill indoor herb garden, a south-facing or southwest-facing window should provide enough sunlight for your full sun herbs throughout the spring and summer months. 

If you want to grow these herbs and you do not have a south or southwest-facing window, you can use a grow light to provide extra light for your plants. The light should be mounted about 18 inches above the plants and kept on for about 10 hours a day. If you are providing light for seedlings, you should mount the grow lights just a couple inches above the tiny plants. 

However, there are other herbs that do not need quite as much sunlight. Some herbs are classified as “partial shade” and can tolerate lower light levels. While these herbs can tolerate lower light levels, they may not be as productive as they might be if you give them supplemental light.

Cilantro, thyme, chervil, Corsican mint, parsley, and angelica are all herbs that you can grow with 4 to 6 hours of dappled sunlight per day.  These plants may grow well on windowsills that face the east or the north. 

If your herbs are getting leggy due to inadequate light, there are several things that you can do to help them out besides giving them a grow light. You can move your indoor herb pots from window to window throughout the day, taking advantage of the sunny patches in your home.

Some people have their herb pots mounted on casters so that they can roll the plants to sunny areas during the day. You can also grow your herbs near a light colored wall and the herb plants will take advantage of the reflected sunlight. Mounting sheets of aluminum foil near your herbs can also help reflect extra sunlight onto your herbs. 

Just because you are enjoying herb gardening inside your home or apartment, doesn’t mean that you will have leggy herbs. You can grow gorgeous, bushy, heathy herbs with sturdy, strong stems when you know how to prune your herbs and provide them with enough sunlight.