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Growing Basil Indoors All Year Long

Basil is an essential and dynamic herb for many dishes.  For the home cook, having easy access to fresh basil can elevate your tomato dishes, stews, and soups.  Innovative cooks have utilized basil to create herbal vinegar dressings for salads, made fritters out of the flower stalks, and even steeped the leaves for a refreshing tea.  These flavors can be missed once the growing season has ended, so let’s explore growing basil indoors!

Basil is a great plant for beginners to practice indoor gardening.  Not much space is needed, and many successfully grow basil indoors on a small sunny window sill.  Growing indoors extends your growing season and you will no longer have to run to the grocery store when a recipe calls for fresh basil. As a side benefit, you can always do a quick crop of basil microgreens along with your main crop!

When you grow basil indoors, you will have an endless supply of this aromatic herb for your culinary dishes. Friends and family will enjoy harvesting basil for their meals, plus they will be impressed with your year-round green thumb!

Ways Of Growing Basil Indoors

Growing basil indoors
Growing basil indoors is very rewarding! Source: SamosBeach

There are a variety of methods to grow basil indoors. Here are a few options!  

Some choose to grow basil in a pot on a sunny windowsill. This method is ideal for those with limited space.  Growing indoors on a windowsill is low-maintenance with direct access to sunlight.  A downside is that cold temperatures can seep through and may shock your warm-loving basil. Your basil may need to be located a few extra inches away from the window to minimize temperature changes.

You may choose to use a grow light with a grow tent. This method gives you complete control over ideal temperature, hours of light, and humidity for optimum growing conditions. It is essentially a mini-greenhouse for your basil.  Downsides include the requirement of more space, it is dependent on electricity, and requires the initial investment of the grow light, tent, fans, timers, and monitoring equipment.  Yet once the system is set up, your basil will thrive!

Another option to growing basil indoors is using a hydroponic system. This is a high-tech method that relies completely on the cycling of water and nutrients.  Hydroponics is gaining popularity because it is more water-efficient and has higher yields than plants grown in soil.  The downside to hydroponics is that it is dependent on electricity, requires frequent fertilization, and the initial equipment cost can be high. 

Caring For Indoor Basil

Growing indoors can be effortless, just as long as you provide the essentials for your plants.  Things to consider when getting started include hours of light exposure, temperature, keeping the soil most, nutrient needs, and what you will be growing in.

Lighting & Temperature

Well lit basil
Basil needs quite a bit of light for best growth. Source: matsuyuki

Basil is a sun-loving plant.  If you are using natural direct sunlight such as a window, you are looking for an ideal location that has 6 hours of sunlight.  If you are in the northern hemisphere, a south-facing window is a perfect spot. For folks in the southern hemisphere, a north-facing window is an ideal location for maximum sun exposure.  Don’t forget to rotate your plants every couple of days or once a week. By doing this, your basil will grow evenly rather than getting leggy as it looks for the sun. 

For those using grow lights, basil requires 10-14 hours a day of light exposure. Depending on your grow light and whether you’re growing a single plant or multiple, you’ll need to make sure your light does its job well. Placing your lights 4-6 inches above young basil leaves is usually fine. For larger mature plants, consider a little taller setting.

Keep in mind that younger plants require up to 16 hours of light.  You may want to experiment with combining sun and grow lights for optimum basil growth.  If the basil starts looking leggy and producing little leaves, you need more light. If yellow or brown spots show up on the leaves, the plants might be too close to the light source.  

Basil plants thrive at warm room temperatures, which makes them ideal for indoor gardening.  The ideal growing conditions for basil are 65-70 degrees Fahrenheit.

Ventilation and airflow are great for basil. This is especially important for grow tents. It is recommended to add some form of air circulation fan that does not directly blow onto your plants. Still, some locations near vents for heaters or air conditioners, or even drafty windows, may make basil more prone to drying out and may slow down its growth.  Make sure to check the soil if your basil is located in these areas, and keep the soil moist but not soggy. 

Water & Humidity

Basil plants love to have their soil on the moist side, but not soggy!   You will want to water your basil regularly.  Make sure to drain any excess water that is sitting in the saucer when you water container-grown basil.  Check the soil by placing your finger into the soil. If it is still wet, hold off on watering.  Young seedlings may require more water. When growing basil in a hydroponic setting, it is recommended to change out your water every 1-2 weeks.  

In regards to humidity, container basil plants like their leaves to be misted once or twice a week in between waterings.  You can fill a pebble tray with water and place it underneath the plant for evaporative humidity.  If you are monitoring the humidity, seek a range between 40-60 percent for your basil.  

Growing Medium & Container

If you grow basil indoors, you have the option to use a nutrient-dense potting mix.  Potting mix provides good drainage for your plant, which is not always true if you’re using soil from your garden.  It can also minimize bringing garden pests into your home.  

Some folks prefer to not have garden dirt in their home, so we’ll suggest alternative soilless potting mixes. Alternatives include most commercial potting mixes (they usually contain no dirt), a home-blended potting mix such as Mel’s Mix, coconut coir, or peat moss. Clay balls are used for hydroponics and are a great tidy medium to use when growing basil indoors in a hydro system.

When growing basil indoors in a container, the ideal size is a 4-inch diameter pot per plant.  Keep in mind that clay pots and saucers are porous, and they may leave marks on your window sill.  Make sure that your pots have drainage holes.  Self-watering containers can also be used for growing basil indoors.  This takes the guesswork out of when to water your plants and keeps the roots moist. 

Fertilizing

Nutrients in the form of fertilizer are an incredibly important food source to grow basil. Rich potting soil holds all of the supplements that your basil requires, but they can be depleted over time. Still, for the lifespan of the average basil plant, starting it off with good nutrient-enriched soil is the best option. Adding a little blood meal or alfalfa meal to your potting mix prior to planting will usually ensure that it has an ample supply of nitrogen to see it through a season’s growth.

Typically, basil is grown as an annual plant. If you manage to coax a longer lifespan out of it, top-dress with slow-release organic fertilizer or additional alfalfa meal/blood meal to again boost the nitrogen levels. It doesn’t take much to keep basil happy.

 For hydroponics, liquid nutrients are the only option.  You will want to add new nutrients every 7-10 days or when your system recommends nutrient additions.

Pruning

Basil leaves
When successful, you’ll have a huge supply of fresh herbs at hand. Source: icherri

To prune or not to prune?  Pruning is not mandatory, yet basil responds well to regular harvesting by yielding more leaves to consume and has a full, bushy appearance.  Wait until your basil is 6 inches tall and prune off the main stem, about ½ inch directly above a set of leaves.  You can use your fingers to pinch off the stem but to prevent tearing the stem you can use scissors.  Try pruning every 2-3 weeks to control the shape of your basil. 

If you allow your basil to flower, or go to seed, this can alter the flavor of your basil and make it tough and bitter. To prevent this turn in taste, you can deadhead the flowers and trim the tops of your basil. 

Planting

Ready to grow basil seeds in a container or grow tent? Pre-moisten your growing medium and plant the basil seeds in a grow tray or the final destination of its container. Cover the seeds lightly with soil. The ideal germination temperature is 75-80 degrees Fahrenheit and sprouts will emerge from the soil in 5-10 days. Be sure to keep the seeds and their medium moist. A seedling heating mat can help you to get the right temperature for sprouting.

If you are planting seeds in a larger container or a hydroponics system, you will want to make sure that you do not overcrowd.  Overcrowding leads to competition for nutrients and limits air circulation. Each basil plant requires 5-6 inches of space. 

You can start seeds directly in a hydroponic system with several seeds in each net pot.  Later, thin and leave the strongest seedling to avoid overcrowding. 

Fresh cuttings of an already existing basil plant can grow roots.  You will need a 4-inch stem with a set of leaves on the top.  Put the stem in water, with the leaves sitting above the water, and place this in a sunny spot.  Change the water daily and roots will begin to emerge in 7-10 days.  Once they have developed to 2 inches long, you can transplant the cuttings into a container or hydroponics system. 

Troubleshooting

Some issues arise when growing basil herb indoors. Often, it can be addressing a simple issue such as too much or not enough moisture or hours of lighting.  There may be temperature changes that are slowing down the growth of your basil.  

Some pesky pests may show up such as fungus gnats, aphids, spider miteswhiteflies, or thrips. You may see small holes or marks on the leaves which may indicate a pest infestation.  To manage this, make sure your basil is not sitting in water and let the top few inches of soil dry out. Pinch off diseased or dying leaves. Treat as required with organic pesticides.

Indoor basil plants can also encounter plant diseases such as downy mildew, bacterial leaf spot, root rot, damping off, and fusarium wilt. You may be able to save the plant from some, but not all of these issues.


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