How to Bottom Water Houseplants (and When Not To)

What bottom watering does

To bottom water a plant, stand its pot in a tray, sink or bucket holding about 1 inch of room temperature water and let the potting mix draw the water up through the drainage hole. Lift the pot out when the surface of the mix is moist, which often takes 20 to 30 minutes. Let it drain and empty the saucer. University of Maryland Extension describes the method in the same terms: water goes into the saucer or an outer container and is absorbed and drawn up into the potting mixture.

The method has two practical advantages. The leaves and the crown of the plant stay dry, which matters for species that mark or rot when water sits on them. And the mix takes up water from the base, where most of the roots are. Clemson Cooperative Extension notes that the bottom two-thirds of a pot holds most of the roots, so that is the zone a watering has to reach.

It has one cost. Water that enters from below never runs out through the drainage hole, so nothing carries dissolved salts away. That is why this page pairs the method with a regular watering from the top.

How to bottom water plants, step by step

You need a pot with at least one drainage hole and a container wide enough to hold it, such as a deep saucer, a tray, a sink or a bucket.

1. Check that the plant needs water. Push a finger into the mix. Extension sources set the depth at 1 to 2 inches: Iowa State and Wisconsin say about an inch, and Maryland and Illinois say about two. If the mix is dry at that depth, go ahead.
2. Add water to the tray. Clemson’s African violet fact sheet uses about 1 inch of water. Use water at room temperature. Clemson gives 62 to 72°F as the range for indoor plants.
3. Stand the pot in the water and leave it.
4. Check the surface of the mix. When it is moist, the soak is finished. This is the end point Clemson gives for both African violets and houseplants in general.
5. Lift the pot out, let the extra water run off, and discard whatever collects in the saucer.

How long step 3 takes depends on the pot, the mix and how dry it was, so sources give different times. University of Wisconsin Extension pours water into the saucer and lets the plant stand 20 to 30 minutes before removing any excess. Iowa State University Extension gives about 30 minutes for a root ball submerged in water. For seedlings in small containers, University of Maine Extension uses a tray of 1/2 inch of water for 20 minutes. Treat those as the time to start checking the surface, and set a timer so the pot is not forgotten.

How to tell when a plant needs water

Bottom watering does not change how often a plant needs water. It only changes the direction. The finger test in step 1 is the most widely given check, and two others back it up.

Weight is the quickest. Maryland suggests lifting the plant, pot and all, to feel the change. A pot that has just been soaked is noticeably heavier than one that is ready for water, and after a few rounds the difference is easy to judge.

Color and fit are the others. Clemson notes that potting mixtures turn from dark to a lighter color as they dry, and that the mix in a clay pot shrinks away from the sides as it begins to dry. For mix that has become very dry and hard to rewet, Clemson suggests placing the pot in a sink or a bucket of water.

A wilted plant is not always a dry plant. Clemson cautions that wilting often signals a need for water but not in every case, and Maryland lists dropped or yellow leaves as a sign of mix that is too wet. Feel the mix before reaching for the tray.

Plants that suit bottom watering

African violets are the plant most often watered this way, and the reasons are specific. According to Clemson, cold water that touches African violet leaves can cause white blotches, and yellow or white ring and line patterns on the leaves come from the same contact. The plants are also highly subject to root and crown rot when overwatered. Watering from a tray with about 1 inch of water keeps the leaves and crown dry, and removing the pot once the surface is moist keeps the roots from sitting wet.

The same logic applies to any houseplant whose leaves and crown you would prefer to keep dry. Seedlings are another good fit. Maine’s seed starting bulletin offers bottom watering as a way to avoid damaging tender seedlings.

Any small or medium pot with a drainage hole can be watered this way if you prefer it. The pot does have to be light enough to lift in and out of the water without strain, since a soaked pot weighs more than a dry one.

When not to bottom water

Skip the method in a few situations.

A pot with no drainage hole cannot take up water from below. If a plant sits in a decorative outer pot, lift the inner nursery pot out and soak that, then return it after it drains.

A plant that already looks overwatered should not go in the tray. Iowa State warns that roots that stay in water for long periods will rot, and yellowing or dropping leaves on wet mix call for less water. The triage steps for that case are in the guide to saving an overwatered houseplant.

Softened water is a poor choice for any watering method. Maryland explains that softened water carries more dissolved minerals than other water and should be avoided for houseplants, and Clemson adds that it puts sodium and chloride into the mix. With bottom watering none of that gets rinsed back out.

Never leave the pot standing in water after the soak is done. Maryland puts it as a flat rule: never let your houseplants sit in water. Iowa State says to remove any excess from the saucer or outer pot after about 30 to 45 minutes.

Why salts build up, and how to flush them

All tap water contains dissolved minerals, and fertilizer adds more. Maryland describes what happens next: soluble salts stay behind and become concentrated as water evaporates from the potting mix. In a pot watered only from below, that evaporation happens at the surface, and no water ever drains through to carry the salts out.

The sign to look for is a pale crust. The University of Georgia’s indoor plant bulletin describes excess soluble salts as a whitish crust on the surface of the growing medium or near the rim of the container, and notes that containers with saucers are prone to the build-up.

The fix is to water from the top now and then. Maryland recommends leaching the soil of houseplants with clear water every four to six months. Clemson’s version of the technique is to apply water until it runs out of the bottom of the pot, which washes out the excess salts, and then to empty the saucer. Wisconsin suggests running lukewarm water over houseplants in the sink or shower from time to time, which rinses dust off the leaves and leaches salts in the same pass. A plant watered from the bottom every time, or one that is fertilized often, is a reasonable candidate for the shorter end of that four to six month interval. The guide to fertilizing container plants covers how feeding adds to the salt load.

Iowa State adds that regular repotting helps reduce salts and metals in the mix. When that time comes, choosing the right pot size keeps the fresh mix from staying wet for too long.

Water quality for sensitive plants

Some houseplants react to what is in tap water. Georgia lists corn plant (Dracaena), ti plant (Cordyline), Maranta and rattlesnake plant (Calathea) as susceptible to fluorine and chlorine. Its suggestion is to let the water stand for several days before use so that some of both is released.

For these plants the periodic flush from the top matters more, because bottom watering alone lets whatever is dissolved in the water stay in the pot. Keep the water at room temperature as well. University of Illinois Extension recommends room temperature water over cold water for houseplants, in line with Clemson’s 62 to 72°F range.