Is Basil a Perennial Herb? How to Grow Basil All Season Long

Basil is a very popular herb in the United States and around the world.

Not only does it look beautiful in the garden, but it also adds flavor and aroma to every dish it is used in. New research has several health benefits.

All this means that many gardeners enjoy keeping basil plants during the summer, and wondering if they can be kept indoors in the fall and winter? This begs the question, is basil a perennial herb?

The short answer is, no basil is not a perennial. It’s actually a annual herb which does not grow back after a year. However, that doesn’t mean you can’t grow it year-round for a fresh supply in the kitchen.

With a better understanding of basil and what it needs to thrive, you might just be able to enjoy the freshest or pesto sauces even when the days are short and the snow piles high outside the window.

In this article, we’ll explore the characteristics of basil as a plant and how to grow it. With a little forethought and a fair amount of ingenuity, you might be able to keep this beloved annual herb like it was a perennial.

What Is The Difference Between An Annual And Perennial Herb?

Annual Herbs

An annual herb is defined by how it carries out its full life cycle from seed to flower to seed again within a single growing season. For some herbs like cilantro, this possibly occurs within the span of six to eight weeks.

Yet other herbs like Greek Oregano the life cycle might need to span from the last frost of spring to the first frost of the fall.

Once the temperatures grow cold, the entire plant dies from stem to leaf and root. Even if temperatures warm again the plant will not come back to life. Meaning there is no “Dormancy” period.

Perennial herbs essentially go dormant during the cold winter months. The root base itself will live on in the next season, though the leaves and sometimes the stems will die or need to be pruned away.

In northern regions where winter can be particularly harsh, the roots might need additional measures to preserve the plants from severe freezing damage.

This usually comes in the form of a thick layer of organic mulch, which you can pull back the following spring.

Perennial Herbs

Perennial herbs are herbs that can live for several growing seasons. There are even some rosemary bushes in Italy that can trace their history back for centuries!

Even in areas where winter is harsh and plants need to be pruned back, they typically return with vigorous growth the next year. Just how long the plant lives can vary by type and conditions.

A particularly harsh winter that affects a young perennial could potentially kill it in the first year. Though most have the potential to live for several years when properly maintained.

It’s worth bearing in mind that with many perennial plants it can take more than one year for them to be considered viable for harvest. Though this tends to not be the case so much with perennial herbs.

It’s also worth noting that there is a special subset of biennial herbs. These plants essentially complete their life cycle within two growing cycles or two years.

Early on, it tends to produce a small number of leaves just above the soil surface. They often spend the first year establishing a strong root mass. Then in the second year, you see more vigorous growth followed by flowering and seed production.

Is Basil A Perennial Or Annual Herb?

Basil is one of the most beloved annual herb which means it does not grow back after a year. It tends to thrive in warm soil temperatures and sunny conditions.

It also has a reputation for not being very cold hardy. Even when temperatures start to drop, yet remain above freezing, the leaves start to thicken and lose much of their prized aroma.

Yet in some warmer climates where frost isn’t a problem, it is possible for basil to live for up to two full growing seasons.

There are also some people who will keep basil in large pots, and bring the plants in for the winter to live in sunny, south-facing window boxes.

There are even some parts of Africa, Asia, and Mediterranean Europe where basil can thrive for more than just one year.

However, in many of these cases, the basil leaves become less aromatic and the plant tends to live more like an edible shrub.

Ultimately, if you live someplace warm, or you have space in a window box or greenhouse, you might just be able to use typically annual basil all year long.

When Should I Start Growing Basil From Seed?

Summer tends to be the time when basil is the most productive. Yet it also cannot bear frost, especially when it’s little more than a tender seedling.

When it comes to starting your own plants from seed, you first need to look up what the “Average Last Frost Date” is for your growing region.

There are several online tools that allow you to simply enter your zip code, and it will tell you the USDA data for your growing region.

You can then start to mark back on your calendar by six weeks from that last frost date. If you live in a particularly warm region, you can grow basil just about any time of year, so long as it never frosts.

However, basil will do better during the long-day periods of the year, as it still needs sufficient sunlight for photosynthesis.

Even if you live somewhere cold, you can still keep potted basil in a sunny window, or inside a properly insulated or heated greenhouse.

Yet, there are still some factors and characteristics of basil that will need to be minded if you want long-term success with this often tender annual herb.

Is It Possible To Grow Basil Year-Round?

Basil can indeed be grown twelve months out of the year, so long as it has the sufficient temperature and light levels it needs to thrive.

Since you will likely be harvesting some of it from time to time, you have to make sure that you can give it everything it needs.

It is possible for basil to linger in barely suitable conditions, then die due to over-harvesting.

Grow Basil Indoors Without Dirt All Winter!

Basil will grow indoors in the winter in cold regions, so long as you meet its necessary requirements. Sometimes it can even be easier to grow it indoors because you have greater control.

There are many gardeners who will grow basil outside in a large pot all summer, then bring it inside to live in a sunny window for a few weeks, just to extend the harvest.

Depending on what you already have available, you will need to account for the following factors in order for basil to thrive.

Use The Right Soil

Basil like slightly acidic, well-drained soil that is also rich in organic nutrients.

A simple light potting mix with a modest amount of organic matter is usually sufficient for feeding the roots of a basil plant. Ideally, you want the soil to be able to retain moisture, without getting soggy.

Overly wet soil can suffocate roots and even cause the stem to rot at the soil level. At the same time, wet soil is increasingly prone to fungi and other plant-borne illnesses.

Ideally, you want to select a bagged potting soil that has been specifically formulated for foliage plants.

You also want the soil to be warm. If you are going to keep basil indoors in a pot, you want it to be a dark color.

Watering it with warm water or putting a heat mat under the soil might also help. Ideally, you want the soil itself to be around 55 to 65 degrees.

Choose Right Pot Or Container Size To Grow Basil In

Basil can become surprisingly root bound. It does best when you plant it in a large bed, box, pot, or container. The roots tend to want to sprawl rather than simply drive down deep.

Whatever container you choose, make sure it has sufficient drainage holes to keep from trapping excess water near the relatively tender roots.

If possible, a heavy-duty plastic pot with a shallow water well, water bank, or collection tray is nice. It makes it easier to move the plant and all the heavy soil around.

Though your standard terracotta pot will also make do just fine. If not sure which one to choose here I are my choices for indoor herb garden planters. 

Place In A Warm Window With A Southern Exposure

Where Should I Keep My basil Plants?

For basil to thrive at a level where you can harvest the leaves without harming the plant, it needs around six hours of sunlight per day.

Ideally, it prefers south-facing light, and morning exposure. A southeast facing orientation is better than western.

When it comes to placing it indoors in the winter, you need to avoid north-facing windows.

Once the Earth passes the autumnal equinox in late September the angle of the sun’s light is too weak the handle the occasional presence in a north-facing window. Basil does not do well in dappled shade.

Use Artificial Lighting For Growing Basil

Can I Use Grow Lights For Basil?

If you simply don’t have the available window space to give basil the south-facing light it craves, you can indeed turn to artificial grow lights.

However, the plant will likely need more time under the artificial light to do well. Instead of six hours of light, they may need up to nine or even ten hours.

There are many different grow light options to consider. Some plants thrive better under one type over another.

In the case of basil, a fluorescent grows light rated for the “Day Light” spectrum is sufficient (Like this one). You can usually set a pair of them in an inexpensive 48-inch shop light fixture.

Then set the light around four to ten inches above the uppermost leaves of the plant. As the basil grows you may need to move the light higher, as contacting the bulbs will likely damage the leaves.

There are some potential minor problems with a 100% grow light approach.

First, the unidirectional nature of the light means that the lower leaves of the plant are going to be deeply shaded.

In time, this could cause them to stunt their growth of “Sulk.” Left unchecked it could even cause the lower leaves to die.

Rotating the plant a quarter turn every day or two will help scatter more light to the lower portions of the basil’s leaves. This is less necessary if your plant is in a window that gets some occasional natural sunlight.

Another issue that can sometimes come up with growing basil and other foliage plants exclusively under grow lights is a purple discoloration under the leaves.

This is typically a sign that the soil is low in phosphorus.

The leaves themselves are still edible, but this is the plant’s way of telling you it needs to be fertilized with a stronger source of phosphorus to promote root growth that can support the photosynthesis potential.

Timely And Thoughtful Watering

Like tomatoes and many other garden plants, basil likes well-drained yet moist soil. Overwatering is a real threat to basil plants and is a somewhat common problem for the first time, indoor herb growers.

It’s best to water the soil when it’s slightly dry. Just make sure not to overwater it to the point where the soil is saturated.

A pot with a “Water Bank” or lower reservoir will also help provide modes moisture to the deepest roots and keep the water from dripping out or making a mess.

What Is Perennial Basil?

There are three types of perennial or biennial basil that you might find in tropical climates. They are: pink, white and Greek. These varieties are native to tropical Asia and part of Africa.

They can be grown in just about any position and will do just fine in part shade as well as full sun.

There are also branching cultivars that grow like a vigorous shrub. Some can get up to three feet tall and sport white and purple flowers on long stems.

Are There Other Herbs That Can Be Grown Year-Round?

Many of the same principles that go into growing basil indoors will also apply to other herbs. Things like parsley can thrive for up to a decade when properly maintained.

You just have to make sure to pot herbs up into a larger container as they age. Left in the same container they can eventually struggle and even die from becoming root-bound.

Herbs to consider keeping in a year-round herb garden include:

• Mint
• Thyme
• Rosemary
• Winter savory
• Ginger
• Chives
• Greek Oregano
• Tarragon
• Sage
• Lavender

In Conclusion

Annual basil like Genovese can be grown in a container and brought indoors to extend the harvest season for weeks if not months after the last frost.

Indeed, there are many people who harvest basil for pesto sauce during the holiday season thanks to things like window boxes, heated greenhouses and of course, a green thumb.

If you want to try your hand at growing basil year-round you just need to remember to keep it warm, keep it moist, but not overly wet, and make sure it gets at least six, preferably eight hours of light each day.