Why Root Rot Happens More Often Than You Think

Root rot isn't something a plant catches like a cold. It's the result of roots sitting in compost that stays wet for too long. Roots need oxygen as much as they need water, and they get it from the air pockets between particles of compost. When those pockets fill with water and stay that way, the roots suffocate, soften and begin to break down. Moulds and fungi that thrive in soggy conditions then move in and finish the job.

In UK homes, overwatering is the single most common way houseplants die. It's an easy mistake to make, because a struggling plant often looks thirsty when it's actually drowning, and reaching for the watering can makes things worse. The good news is that once you understand a few simple principles, root rot becomes almost entirely avoidable.

How to Check Whether Your Plant Actually Needs Water

Forget the calendar. The only reliable way to know if a plant needs water is to check the compost itself. Sticking a finger in is still the best tool you own.

• Push your finger 2–3cm into the compost for most plants, or about 5cm for large pots. If it feels damp, wait. If it feels dry, water.
• Lift the pot. A dry pot feels surprisingly light; a saturated one feels heavy. This takes practice, but it's quick and reliable once you know your plants.
• Look below the surface. The top centimetre can look bone dry while the bottom half of the pot is sodden, particularly with peat-free mixes that become water-repellent at the surface.
• Consider a moisture meter if you have big pots, cacti or succulents. They're inexpensive and take the guesswork out of it.

Do this check every few days rather than watering on a fixed day of the week. A plant that needed a drink last Tuesday may not need one this Tuesday.

How Often to Water Different Houseplants

Treat these as starting points and adjust to your home, your light levels and the season. A plant in a bright, warm room dries out far faster than one in a cool, shaded corner.

• Succulents, cacti, snake plants and ZZ plants: let the compost dry out completely. Roughly every 2–4 weeks in summer, and as little as every 6–8 weeks in winter. They store water in their leaves and stems.
• Pothos, spider plants, philodendrons and rubber plants: water when the top 2–3cm is dry — about every 7–10 days in the growing season, stretching to every 2–3 weeks in winter.
• Peace lilies, monsteras, calatheas and ferns: keep the compost lightly moist, watering when the top centimetre or two dries. Roughly weekly in summer, every 10–14 days in winter. These dislike both drought and waterlogging.
• Orchids: don't water on a schedule at all. Soak the pot for 10 minutes, let it drain completely, and repeat only when the bark or moss has dried out.

From November to February, most houseplants are semi-dormant thanks to lower light levels. Nearly every plant needs less water in winter than in July.

Why Drainage Matters for Healthy Roots

A pot without drainage holes is a container, not a planter, and water has nowhere to go. Every pot you use should have holes in the base. If you love a decorative cachepot with no holes, use it as an outer sleeve and always keep the plant in a plain inner pot.

• Empty saucers and cachepots about 20 minutes after watering. A plant left standing in water will wick it back up into the compost.
• Terracotta breathes. Unglazed clay lets moisture evaporate through the sides, which suits plants that hate wet feet. Plastic and glazed pots hold on to water for longer.
• Skip the layer of crocks. Gravel in the bottom of a pot raises the saturated zone rather than improving drainage. Use a freely draining compost instead.
• Match the pot to the plant. A small plant in a huge pot has lots of compost and few roots to drink it, so it stays wet for weeks.

If your compost has broken down into a dense, airless mush, repot into fresh mix in spring. Roots need those air pockets back.

Watering Technique, and Dealing with UK Tap Water

When you do water, do it properly. Pour slowly over the surface until water runs out of the drainage holes, then stop. Little frequent sips encourage weak, shallow roots and allow salts to build up in the compost.

Use water at room temperature, as a cold blast straight from the tap can shock tropical roots. In hard water areas, limescale causes brown leaf tips on spider plants, calatheas and dracaenas — filtered or rainwater makes a real difference, though most plants cope fine with tap water. Bottom watering, where you stand the pot in a tray of water for 15–30 minutes, suits plants with dense foliage or fuzzy leaves. Avoid pouring water into the crown of plants like aloe, snake plants and orchids, as this invites rot at the base.

Signs You're Overwatering — and How to Rescue a Plant

Yellowing lower leaves, soft or mushy stems, a sour smell from the compost, fungus gnats, and a green film of mould on the surface are all classic warnings. Confusingly, underwatering also causes yellow leaves, so always check the compost before acting.

If you suspect root rot, stop watering immediately and move the plant somewhere brighter. Tip it out of its pot and inspect the roots: healthy roots are firm and pale, rotten ones are brown, slimy and fall apart. Trim the damaged roots with clean scissors, repot into fresh, freely draining compost in a clean pot, and leave it a few days before watering again. If rot has reached the base of the stem, take cuttings from healthy growth — they'll root happily and give you a fresh start.