How Often to Water Basil : Getting It Just Right

Overwatering and underwatering your basil plant can lead to problems. Are you watering correctly?

Basil is a tender annual herb that likes a consistently moist, but not wet, soil.  So, water deeply and thoroughly whenever the soil is dry to the touch.  This can be a little tricky to master at first – basil can be a bit of a Goldilocks – but with a bit of practice you can get it “just right.” 

Knowing how often to water depends on where, when, and how you are growing it.  Weather conditions are a big factor.  If you are growing it in a full sun garden in July, you will need more water than if you are growing it on a winter window sill. So “how often should I water?” can mean different things at different times of the year, and in different environments.

Basilicum ocimum is a member of the mint family and is native to India.  The most common is sweet basil, but there are other varieties to try and they all need the same growing conditions:  warm temperatures, at least six hours of full sun daily, and a well-draining moist soil.  It requires more water than herbs from the Mediterranean area – such as oregano, thyme, and rosemary – which prefer drier conditions.  

Proper watering will keep your plant healthy and happy, and that keeps new leaf production high and the flavor optimized.  Fresh, tender, tasty leaves are what it’s all about!

Watering Frequency When Growing Indoors

Water when the top half-inch of the soil is dry to the touch.  Depending on how much sunlight your plant gets and how warm and dry the room, this could mean you might need to water every few days. On dark, cloudy winter days, you may only need to water weekly. Plants in small flower pots will need to be watered more frequently than those grown in larger containers.

The benefit of growing indoors is that you’ll be able to have basil in the summer or the winter.

Watering Frequency When Growing Outdoors

When you grow basil outdoors, it will need 1″ to 1-½” of water per week.  That water can come from your garden hose or from nature. It’s best to deliver water in one-third increments throughout the week, but sometimes the weather doesn’t always cooperate. So if you get an inch of rain on Tuesday and the following days are hot and sunny, you might need to water again on Friday or Saturday.

You can set out empty tuna fish or cat food cans to measure how long it takes for your garden hose or sprinkler to put out an inch of water.

basil plant that is wilting outdoors

In Gardens

Basil planted in the ground will need smaller amounts of water delivered more frequently after you first plant it.  As the season progresses and the roots develop, you will need to water less often but for a longer period of time.

Using organic mulches such as straw, shredded hardwood mulch, or grass clippings can help moderate the soil’s moisture and keep your plant’s roots cool during the hottest months of the growing season.  Keep the mulch a little bit away from the crown of the plant – do not build a little mulch volcano around the stem.

A soaker hose under the mulch or a drip irrigation system on timers can do a lot of the work for you, but you still have to personally check on your plants once in a while – at least weekly.

In Outdoor Containers

In container gardens, you can use the companion planting concept and grow it with other moisture-loving herbs such as mint, chives, and other varieties – try globe, lemon, Thai or Italian basil.  And, of course, basil and tomatoes get along in the garden as happily as they do on your plate.

When planting in outdoor containers, you may need to water every day, depending on the weather and the container’s size.  Again, check the top of the soil and also check a little further down.  If you can pick up the container, the weight of the pot can be a clue to watering needs.  If the pot feels light, it needs water; a heavy pot probably doesn’t.  Also, look at the soil through the drainage holes to see if it is moist throughout.

Watering too much or too little are both bad

Underwatering vs. Overwatering:  How to Tell the Difference

People tend to overwater indoor plants and underwater outdoor plants. While both underwatering and overwatering can causes plants to wilt, there are ways to tell the difference.

Recognize What a Healthy Plant Looks Like

If you are frequently using your basil for cooking (and we certainly hope you are!), you can easily judge the health of your plant every time you snip a handful of leaves.

A healthy plant has a naturally droopy appearance.  The leaves are puckered and have a natural tendency to turn under slightly along the edges and the tips of the leaves point downward in a gentle curve.  A properly watered plant has strong, firm stems, bright green new growth, and when you rub a leaf between your fingers, it has a slight give, and it releases a wonderful fragrance

Basil’s droopy look should not be mistaken for wilt.  A wilted plant will have stems that curve downward and the leaves will be almost flat against the stem.  In severe cases, the entire plant will be flat and shriveled.

Healthy basil leaves should be slightly droopy, but not wilty

Signs of Overwatering

Overwatering signs include: wilting even though the soil is wet, yellowed leaves that drop off, and a darkening of the stems.  Blisters or corky bumps may appear on the leaves – this is edema, a condition that develops when a plant takes up more moisture than it can use. The top of the soil may have a greenish tinge, an indication of algae growth, which is a sign of too frequent waterings. An overwatered plant is susceptible to fungal diseases and root rot.

Signs of Underwatering

An under-watered plant will have leaves that look dusty, dull, or pale.  As the need for water increases, the leaves become dry and brittle. The soil will be dry and may even have shrunken away from the sides of the pot.  It is possible for the top of the soil to be moist and the rest of the soil to be dry, so check down an inch or two.

A clearly underwatered basil plant

8 Watering Tips

To make sure your plant is receiving the correct amount of water, here are a few additional tips to help you get it just right:

  1. Check the general health of your basil plant frequently.  After a while, you will know when your plant needs water just by looking at it.
  2. Remember that the soil should always feel slightly moist – like a damp sponge.
  3. Don’t mistake a cold soil for a wet one.  A cold dry soil can feel wet to the touch, especially in winter. 
  4. Water plants that are grown outdoors early in the morning.  This simple step will keep it from drying out as the day heats up.
  5. Sometimes the top of the soil is wet, but down where the roots are, it’s dry.  Use a wood skewer, or even your finger, to check soil moisture deep down.
  6. Water plants in containers until the water runs out the drainage holes.  For indoor basil, you can do this at the kitchen sink and use the sprayer hose.  Water gently and water the entire surface of the soil, not just in one spot.   Be sure it’s finished draining before you put it back on the windowsill!
  7. As your plant grows, its watering needs will increase. Pruning can reduce watering needs or you can consider repotting, especially if its roots are growing out of the drainage holes.
  8. Don’t let your basil plant dry out.  But if it does, don’t despair.  It can be saved.  First, move your plant out of the full sun if it’s in a container.  Then water deeply and thoroughly.  After a few hours, water again.  Once all the moisture in the soil is taken up by the plant’s vascular system, the soil is dry again.  A second watering ensures that there is moisture available when the plant needs it.  Otherwise, you will just be repeating the cycle.  
An example of a thriving healthy plant with the correct amount of water

And remember to feed your basil plants, pinch and prune, and deadhead the flowers to keep your plant in optimum, tasty condition. 

Alaine Connolly
Alaine has been working way too hard in horticulture since 1992, beautifying golf courses, resorts, and hotels. She is a part time landscape designer who works full time caring for a 28,000 square foot public garden. At home, she maintains her own 400 square feet plot. Alaine lives in northern Illinois - zone 5b.
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