How and When To Water Houseplants

You cannot successfully grow houseplants by watering them on a schedule or routine. This is where most plant parents go very, very wrong, and this is the main reason why most houseplants die. They are overwatered. Still convinced you’ve got a black thumb? Chances are very good you just overwater.

A houseplant’s watering needs are constantly changing, and your watering habits need to change as well. You’ll need to adapt to each plant’s watering needs, and if you think that the plant will adapt to your schedule it may appear to adapt — as it dies a slow and torturous death. This isn’t to say you shouldn’t own or buy houseplants. But if you want them to survive and thrive, you’ll need to learn how and when to water them.

For most houseplants it’s hard to go wrong by watering the plants thoroughly until the water runs out of the drainage holes in the bottom of the pot. There should be a saucer under the pot that will hold the water that runs out of the drainage holes. Continue to add water until you see the water begin the fill the saucer then stop. Don’t empty the saucer right away though. Allow the plant to sit in the standing water for about 15 minutes then empty the saucer. Plants should never be allowed to sit in standing water for more than 15 minutes.

An alternative way to water is to fill the saucer under the pot with water and allow the water to be soaked up. This works best with clay pots as the clay tends to absorb the water and the capillary action of the soil in the pot will wick up the water. Refill the saucer until the pot and plant stop absorbing it then remove any excess.

This will work for most plants, but when watering from the top take care not to allow a strong stream of water to come out of the watering can to the point where it disturbs the soil. Slow and gentle is the rule. When the watering is done don’t add any more water until the soil surface dries to about the depth of one inch. Let your index finger be your guide. Your finger allows you to not only detect the moisture but the depth or lack of moisture.

The rules are different for succulents, especially cacti. Cacti generally should be watered no more than once every two months in the winter and once a month during the summer. Remember their origins? Most come from arid areas or deserts. There is one short “rainy” season and the rest of the year just an occasional passing shower. It’s also the nature of cacti to be able to store water very efficiently, and this is usually seen in their shapes and sizes.

Then there is a group of plants that absorb much of their moisture from the air and not from their roots. The best example of these plants are the terrestrial orchids. These plants generally grow on tree trunks or branches using their roots primarily for anchoring and some absorption of moisture from the saturated, humid air. This is why most orchid potting soils really contain little to no soil and mostly bark mixes, which the roots anchor to. The bark absorbs some moisture but never remains dripping wet and drains very quickly.

Remember in the beginning of this series when I mentioned that it was the invention of plastic pots that brought about the houseplant revolution? Well, about 15 years later it also brought about a revolution in the propagation and marketing of orchids. Prior to the use of plastic pots orchids were always sold in heavy clay pots or in wooden lattice pots. The lightweight plastic pots presented new opportunities and serious issues.

Orchids don’t like sitting in wet soil. Plastic pots tend to retain soil moisture much more than clay pots. As a result, plants in clay will require more watering than the same plant in a plastic pot. So, how do you grow an orchid in a plastic pot if the soil stays wet? Simple, you use a different soil that’s mostly composed of bark, add a few more drainage holes and now all the orchids you find in retail shops are in plastic pots with perfect drainage. Of course, the breakthrough in cloning and orchid propagation helped as well, but orchids are now nearly as ubiquitous as other houseplants.

Your tropical foliage will also give you hints when they need water. They don’t exactly wilt but many of these plants will express soil dryness in the foliage pointing down instead of out, as in a Dracaena marginata, or the foliage will have a droopy appearance as happens to a Schefflera.

What does it mean when you water your plant one day and either that day or the next day it’s dry and droopy again? It means your plant is pot-bound and the roots have taken over so much of the soil mass that the soil can no longer absorb enough water to supply the plant with its needs. It’s time to repot. You can do a simple test for this by watering the plant well then popping it out of its pot. If all you see once it’s depotted is roots going round and round and round — it’s repotting time. I’ll get into repotting early next year as spring is really the best time to repot.

I’ve yet to find the perfect watering can for houseplants. Most are too big, and they tend to put water everywhere but right into the saucer or on top of the soil. You don’t want water spilling all over the place, but some plants may take several ounces to quarts of water at each watering. Be inventive.

I found one plastic watering can (a Haws Bartley Burbler 2-pint, $16) with a removable rose (the perforated watering end of the spout) that always got clogged and was useless for smaller pots. I removed the rose and added a 7-inch length of vinyl tubing with a 3/8-inch inside diameter (available by the foot at hardware stores) that naturally has a slight curve to it. The length of the spout with the added tubing allows me to water any of my plants without spilling a drop of water and keeping the foliage dry as well.

The other watering can I mentioned last year isn’t a watering can at all but an old-fashioned oil can. The spout is a bit flexible so it can be curved a bit just like the vinyl tubing so there’s no spilling and the water goes right where you want it.

Lastly, don’t use potting soils that have water-retaining crystals. These crystals or beads are a form of a hydrogel that absorbs more water than the soil alone can. It was a great idea, but it also leads to even more problems with overwatering as it often kept the soil much too wet for much too long.

To review: Never use pots that don’t have drainage holes, especially decorative glazed pots or ceramic pots. Be aware that a plant in a plastic pot will dry out much more slowly than the same plant in a clay pot. There are specialty pots made from clay and plastic with drainage slats on the sides as well as holes on the bottom. These are mostly for orchids. Water most plants well once and let them dry out (use the finger test) before watering again. In most cases, a plant that wilts or dries out quickly — a day or less —needs repotting and not more water. Always use water that’s at room temperature.

And if you absolutely need an assist then buy an inexpensive moisture meter. They cost under $20 and will allow you to skip the index finger test by simply pushing the probe into the soil and watching the needle on the meter. It’s a learning tool, not something to get dependent on. Much better to know your plant than to rely on a device.

So, there you have it. The basics of Houseplants 101 and what I hope will be a guide to your jungle or desert of success. As I noted, we’ll cover repotting later in the winter as well as how to feed your plants and when, and the small list of houseplant insects and how to manage them. Let me know how you’re doing and as always, keep growing.