All houseplants need water to keep them alive, but how much depends on their country of origin and the environment they evolved in. For example, a plant native to the jungles of South America will need more water than a cactus from the Mexican desert. Knowing how much water to give your plants is key to their survival.
What’s more, it pays to know the signs of under- or over-watered plants. Plants will ‘tell you’ if you’re not doing it right. We’ve identified some of the most common signs of under- and over-watering, below. Learn to read the signs and you’ll be better equipped to give your houseplants exactly what they need.
Not enough water
A wilting plant
Plant leaves are full of tiny, water-filled cells that help them retain their shape. If not watered regularly, the cells shrink and the leaves begin to wilt. Most wilted plants recover quickly after watering, but it’s best not to let them wilt regularly. Instead, look for other signs such as dry compost. If compost feels dry to the touch, then water. Dry compost also looks pale and weighs less than when damp, so if in doubt, lift your plant to see if it’s heavy. If the compost is really dry it may shrink away from the pot, so any water will run straight through. If this happens, stand the pot in a basin filled with water and leave it there until the compost has expanded again.
When your house plant is too wet
Drenching potted leaf cuttings with a fine rose watering can
Over-watering can kill a plant, but there are signs to look for before this happens. The best way to know if you’re over-watering is to check the compost – if it feels damp, don’t water. Other signs to look for include a stagnant smell and even green or mouldy patches on the surface of the compost, and clouds of fungus gnats, which breed in damp conditions. What’s more, over-watered plants may lose their leaves or their leaf tips may turn black or yellow. Over-watered orchids, cacti and succulents may turn soft, before rotting. If you spot any of these signs then stop watering immediately. Check any tray or plant pot to make sure the plant isn’t sitting in water, and allow the compost to fully dry out before watering again.
Seasonal differences with houseplants
Watering a houseplant with a small watering can
A plant’s watering needs change from season to season. For most plants this is due to the heat and light levels associated with the time of year. Plants that thrive on weekly watering in spring may need watering twice weekly in summer, especially if they’re positioned near a south-facing window. During the cool days of autumn and winter, most plants don’t grow much, so reduce watering and, as ever, check the compost if in doubt.
Houseplants that require different watering
While the above rules work for most houseplants, there are some that need special treatment. Carnivorous plants hail from bogs and marshes, so they need wet compost at all times. At the opposite end of the spectrum, desert cacti and succulents need much less water. In summer, water these regularly, but in winter give only the bare minimum to succulents and keep cacti completely dry. Orchids can be challenging as their potting compost always looks dry, but don’t be tempted to water too often as their fleshy roots may rot. With moth orchids (Phalaenopsis), wait until the roots look a silver colour before watering (the roots turn green when wet).
Feature by Dr. Ross Bayton.
Insect-catching traps of a carnivorous plant