How Often to Water Basil So It Stays Healthy All Season Long

Basil—like so many other herbs—is super easy to grow, making it a staple in any edible garden. But even though it’s low-maintenance, knowing how often to water basil can be a little tricky, as its watering needs will vary depending on a number of factors. To keep you from over or underwatering this herb, we spoke to gardening experts who shared their best advice for keeping this popular herb healthy.

How Often to Water Basil 

Basil's water requirements vary depending on how mature the plant is, as well as whether it is potted or grown in the ground.

How Often to Water Basil Seeds

When growing basil from seed, the soil should be kept evenly moist without allowing it to dry out. You can keep moisture in by placing a plastic cover on top of your seed starting trays or pots, but promptly remove it as soon as you see any green. "I prefer using a gentle spray bottle when starting seeds, even if it means checking for moisture twice a day by touching the soil surface," says Kim Roman, instructor for Square Foot Gardening.

How Often to Water Seedlings

As the young basil seedlings slowly mature, gauge the moisture content of the soil by touch. “When the plants are about 2 inches tall, gently stick your finger about an inch away from the stem, up to your first knuckle,” says Roman, adding that you should water when the soil feels dry.

How Often to Water Mature Basil Plants

There are several factors that determine how much and how often you will need to water mature basil plants, like how much sunlight they have, your soil quality, and how big the plant is. “In general, basil needs at least 1 to 2 inches of water per week, and more if the weather is extremely hot, or if it hasn’t rained," says Roman. To determine if your plant needs water, stick your finger into the soil up to your second knuckle and water when it feels dry.

How Often to Water Potted Basil

Generally, potted basil needs to be watered more often than basil grown in beds. To know if your potted basil plants need water, stick your finger into the soil about 1 inch down. If it's dry, give your plant a drink. Additionally, if the drainage holes are dry, you should also water your plant. "Over time, you can adjust your frequency once you get a handle on your growing conditions (sun, heat, rain, soil, etc.) impact the plant," says Lorraine Ballato, garden author and speaker.

Factors to Consider When Watering Basil Plants

Beyond age, a few other factors will play a part in determining the watering schedule for your basil plants.

Sunlight

While basil is a sun-loving plant, it appreciates a bit of afternoon shade. In full sun, basil will dry out faster and thus need water more frequently. If the area is too sunny, Roman recommends using a shade cloth.

Humidity and Temperature

Generally, the higher the temperature and the lower the moisture, the faster your soil will dry out. “When the weather is cooler, you’ll probably only need to water once a week, but start checking after five days,” says Roman. “On very hot days, above 90 to 95 degrees Fahrenheit, you will likely need to water every day, or even twice a day.”

Soil Quality

Basil prefers fertile, well-draining soil. “If your soil is too sandy, you’ll need to water more often, or better yet, add compost to help hold more moisture,” says Roman. But you also want to avoid overly heavy soil that retains water excessively. “If your soil has too much clay, basil won’t grow very well unless you add some construction sand, vermiculite, and compost,” she says.

Container Type

The watering schedule for potted basil may vary depending on the type of container the herb is in. “You will water less if you’re planting in plastic or resin pots,” says Roman. “If growing in terracotta pots or fabric grow bags, you will need to water more often.”

How to Water Basil 

It's essential to avoid getting the leaves of your basil plant wet when you water it. This is due to basil downy mildew (Peronospora belbahrii)), a fungal disease specific to basil plants, says Ballato. Aim to water at ground level to prevent splash-ups. “At the first sign of yellowing leaves, you must immediately inspect for the disease as the spores are fast-moving," she says. "It's also best to water in the morning, which gives the basil foliage time to dry before nightfall (when the pathogens do their dirty work)."

Signs Your Basil Plant is Underwatered 

Dry and drooping leaves are telltale signs your basil is being overwatered. “Check on your basil at the first sign of drooping leaves, but don’t automatically assume this means they need water," says Roman. "Test the soil with your finger as explained above. If they are in desperate need of water, the leaves will become dry and crispy, then eventually turn brown."

Signs Your Basil Plant is Overwatered 

With all your careful watering of your basil plant, you also have to watch out for the possibility of overwatering. “Overwatering can be just as much of a problem as underwatering,” says Roman. 

Too much moisture in the soil can stifle the roots’ access to oxygen, which can shut down critical biological processes. “Overwatered basil will develop yellow leaves at the top of the plant. But that leaf discoloration could also be caused by something else,” says Ballato. “So again, it's best to stick your finger in the surrounding soil to test for wetness.”