Watering and Drainage: Avoiding Waterlogged Roots

Why vegetable pots need more water

Garden vegetables grow faster than indoor houseplants and soak up more sun, so they use far more water. Bushy cherry tomatoes and peppers in particular can dry their pots out quickly on summer afternoons. That doesn't mean constantly wet soil is good, though. Roots get oxygen from the air between soil particles, and if water fills those gaps for too long, the roots suffocate and rot. The key is a rhythm that gives the soil time to dry somewhat, then soaks the whole pot thoroughly when you do water.

When and how much

The basic rule is to water when the top inch or two of soil is dry, and to keep going until water runs out of the drainage hole. Little and often wets only the surface and leaves the lower roots dry, so the roots stay shallow. Lifting the pot works well too. Compare its weight right after a thorough watering with its weight when dry, and from then on a quick lift tells you what you need to know. Go by the weather and the soil rather than a fixed schedule, but make checking a daily habit. Setting a reminder for a check time helps you not forget.

• Check with a finger whether the top soil is dry
• When watering, keep going until it drains out
• Empty saucers right away
• Gauge dryness by the pot's weight

Water in the morning, at the soil

Water in the morning when you can. Plants use the water during the day, and any droplets on the leaves dry while the sun is out. Wetting leaves in the evening keeps them damp overnight and invites fungal disease. Rather than sprinkling over the leaves, pour slowly onto the soil around the base of the plant. Pouring hard digs into the soil and splashes muddy water onto leaves, which can spread disease. Instead of suddenly dumping cold water into a pot baking in the midday sun, it's easier on plants to water early in the morning or after the sun drops. If leaves droop at midday but perk up by evening, it may be temporary, so check the soil first.

By season and growth stage

Right after transplanting, seedlings wilt easily because their roots haven't settled into the soil yet. For the first few days, keep the soil from drying out too much, and shielding them briefly from harsh direct sun reduces transplant shock. As plants grow and put on more leaves, they use more water, and more still once fruit sets. On the other hand, on cool spring and autumn days, cloudy days and during the rainy season, soil dries slowly, so water less often. With fruiting crops, repeated swings from bone-dry soil to a sudden heavy watering make fruit prone to splitting, so water as evenly as you can.

Checking drainage

If water sits on top instead of soaking in, or runs down the edges and straight out, something is wrong with the soil. When soil is so dry that it repels water, setting the pot in a basin of water for a while to wet it from below will restore it. If the soil has compacted, gently loosen the surface, and in severe cases consider repotting. Check that the drainage hole isn't blocked by roots or soil and that the saucer isn't always full of water. Pot feet that lift the pot slightly off the saucer keep the hole clear and let air through.

• Water pools on top: compacted soil or a blocked hole
• Runs down the edges: soil too dry
• Saucer always full: water less and empty it
• Musty smell from the soil: a sign of overwatering

Mulch and saving water

A thin layer of dry straw, shredded leaves or bark over the soil cuts evaporation so the soil dries more slowly, and it stops soil splashing when you water. On a balcony that's always damp, though, the soil under the mulch can get too wet, so keep an eye on it. If you grow several pots, grouping them close together raises the humidity around them slightly and slows drying. Some people use collected rainwater or the water from rinsing rice, but rice water left standing can cause odors and gnats, so use it right away and not in large amounts.

When you're away for a few days

If you're traveling for a few days, water thoroughly the day before you leave and move pots into bright shade with less direct sun so the soil dries more slowly. You can also run a fabric wick from a container of water into the pot's soil so water rises gradually, or push an upturned bottle of water into the soil. Whichever method you choose, test it a few days ahead and see how much water it delivers per day. Filling saucers to the brim can lead to waterlogging if it goes on for more than a few days, so use that only for short trips.