How Often to Water Basil and When to Feed It

Dry soil makes small, tough leaves

Basil wants water. Kept dry, the leaves thicken and harden and the edges roll inwards. Even without visible wilting, a plant grown on the dry side gives you leaves with a texture that is no good in a salad.

Constantly saturated compost damages the roots, though. Let the surface dry, then water until it runs from the bottom. That rhythm, rather than a constant trickle, is what keeps the leaves soft. Do not leave water standing in the saucer.

1. Water thoroughly in the morning In summer, water in the morning until it runs from the drainage holes. Small top-ups through a hot day never reach the depth the roots are at.
2. Judge the evening by the plant If the leaves are drooping in the evening, water again. If not, wait until morning. Decide by the plant, not the clock.
3. Empty the saucer Water left standing starves the roots of air and the lower leaves yellow. Tip it away after every watering.
4. Mulch the surface Covering the soil slows drying and cuts the number of waterings in summer. Straw in the ground, bark chips in a pot.

Leaves that have gone tough never soften again. The quality returns with the new leaves the plant makes after you fix the watering.

In summer a small pot dries out in a day

On a hot summer day, basil in a small pot will not last from a morning watering to the evening. The leaves are large and it loses a lot of water. Let it droop in the evening repeatedly and the plant starts rushing into flower.

If you are going away, move pots into half shade to cut water loss. That is more reliable than an automatic waterer left in full sun.

Allow about a gallon of compost per plant

The smaller the pot, the faster it runs out of both water and food. Basil roots spread rather than go deep, so the volume of compost matters more than the depth. About a gallon and a quarter (5 L) per plant, at least eight inches (20 cm) deep, makes summer far easier.

1. Use a compost that holds water An ordinary multipurpose vegetable compost is fine. A very free draining sandy mix dries too fast in summer and that alone will toughen the leaves.
2. Three plants to a trough A standard 26 inch (65 cm) trough holds three to four gallons. Three plants is the limit. Four or more and it will not hold water through summer.
3. Use a pot at least eight inches across For a single plant, eight inches (21 cm) is the minimum. Anything smaller commits you to watering twice a day in high summer.
4. Terracotta dries fast Unglazed terracotta breathes well but dries quickly in summer. If you are often away, choose plastic or a thick resin pot.

Feed every two to three weeks

Pinching repeatedly and cutting leaves all season is demanding on the plant. When it runs short of food the leaves get smaller and paler and it flowers early. Start feeding about three weeks after planting and keep it up every two to three weeks.

Too much nitrogen gives you plenty of leaf with less scent. Stick to the dilution on the label rather than making it stronger.

Light and where to put it

Basil grows best at 77 to 86F (25 to 30C) and wants sun. It survives in part shade but the shoots stretch and the leaves thin out. In the hottest part of summer, though, a spot in strong afternoon sun dries too fast and toughens the leaves, so somewhere shaded from mid afternoon is ideal.

1. Full sun in spring and autumn While temperatures are around 68F (20C), the more sun it gets the sturdier and more compact it grows. Indoors, a south facing window.
2. Shade from afternoon sun in high summer A pot standing on concrete in afternoon sun gets far too hot. Raise it on a slatted stand and move it where a building shades it after midday.
3. Give it moving air A bushy plant traps still air inside and the lower leaves drop off black. Keep it off the wall and leave gaps between plants.

Grown entirely indoors, basil does not get enough light: the shoots stretch and the scent weakens. Put it outside on fine days.

Reading the leaves

Changes in leaf color and shape each have their own signature. Work out whether the problem is water, feed or cold before you act, or you end up feeding a plant that is simply short of water and make it worse.