Soggy compost is the quiet killer

Most container plants don't die of thirst. They die of kindness. A plant left dry for a day or two will usually wilt, sulk and then recover the moment you water it. A plant sitting in permanently wet compost is a different story. Roots need oxygen as much as they need moisture, and when every pore in the compost is filled with water, they can't breathe. The roots suffocate, rot sets in, and by the time the leaves yellow and drop you're dealing with damage that's hard to undo.

So the goal isn't to keep compost damp at all times. It's to water thoroughly, then let the top few centimetres dry out before you water again. That wet-dry cycle is what healthy roots want.

Check before you pour

Before you reach for the watering can, spend ten seconds finding out whether the plant actually needs a drink.

• The finger test. Push a finger about 2–3cm into the compost, near the edge of the pot rather than against the stem. If it feels cool and damp, walk away. If it feels dry, water.
• The weight test. Lift the pot. A freshly watered pot is surprisingly heavy; a dry one feels light and hollow. Do this regularly and you'll soon judge by heft alone — the best trick for large pots you can't easily poke a finger into.
• The tap test. Rap the side of a terracotta or plastic pot with your knuckles. A dull thud suggests moisture; a hollow ring suggests dry compost.
• A moisture meter can help if you're unsure, though readings vary between peat-free mixes, coir and loam. Treat it as a second opinion, not gospel.

Small pots, hanging baskets and seedlings need checking daily in summer. Big planters of mature shrubs might need it only twice a week.

Drainage is not optional

Every container you plant into needs drainage holes. No exceptions. If you've fallen for a beautiful glazed pot with a sealed base, use it as a cachepot: stand a smaller nursery pot with holes inside, water that, and empty the outer pot half an hour later.

There's an old habit of filling the bottom of a pot with gravel or broken crocks "for drainage". It doesn't help. It raises the saturated zone inside the pot and gives roots less room. Use a single crock or a piece of mesh over the hole to stop compost washing out, then fill with compost.

• Never let pots stand in a full saucer of water for more than half an hour. Empty it. In a heatwave a shallow puddle can be a lifeline for thirsty plants, but not as a permanent arrangement.
• Raise pots onto feet in winter so water drains freely and doesn't freeze around the base.
• Open up your compost. Peat-free mixes vary a lot. If yours looks dense and claggy, fork through 20–30% perlite or horticultural grit to keep air moving.

Water properly when you do water

Little and often is the commonest mistake. A quick daily splash wets only the surface, leaving the lower compost bone dry and encouraging shallow, vulnerable roots. Instead, water slowly and thoroughly until it runs out of the drainage holes, then stop. That flushes stale salts away and wets the whole rootball.

Use a watering can with a rose for gentle delivery, and water the compost, not the leaves. Wet foliage, especially in the evening, invites mildew and damping off. For big pots, give the compost time to absorb rather than letting water channel down the sides.

Adjust for weather, season and pot

There is no watering schedule that works all year. Frequency depends on the day, the plant and the pot.

• Hot, windy days. Wind dries containers faster than sun alone. Small pots can need water twice a day in a July heatwave; a sheltered shady corner may need it once a week.
• Water in the early morning where you can. Compost is cool, evaporation is lower, and foliage has all day to dry. Early evening is a decent second choice — water the soil, not the plant.
• Rain doesn't always count. Pots under eaves, against walls or beneath leafy canopies often stay dry through a downpour. Check anyway.
• Winter. Cut right back, but don't forget containers under cover — they can dry out completely and, paradoxically, die of drought in January. Water sparingly on mild mornings, never in a hard frost.
• Terracotta breathes and dries fast; glazed and plastic pots hold moisture longer. Dark pots in full sun cook roots, so consider shading or moving them.

Reading the warning signs

Overwatering and underwatering can look oddly similar — both cause wilting — so always check the compost before acting.

• Overwatered: yellowing lower leaves, wilted growth despite wet compost, soft brown or black stems, a sour smell, fungus gnats, green algae on the surface.
• Underwatered: compost pulling away from the sides of the pot, crispy leaf edges, wilting that recovers overnight after watering.

If a pot has been waterlogged, stop watering, move it somewhere airy and out of direct sun, and let it drain. Root rot can't be reversed, but if healthy roots remain, repotting into fresh, open compost gives the plant a fighting chance.

Water thoughtfully, and your containers will reward you with steady growth all season.