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Watering technique

Also known as How to water, Top watering, Bottom watering

Growing know-howDepends
Watering cans of assorted sizes Photo: Bas Leenders at https://www.flickr.com/photos/basl/ · CC BY-SA 2.0

In short

Water when the plant needs it, not by the calendar, and when you water, water thoroughly until it drains, then empty the saucer. Overwatering is about watering too often, not about the amount in one go.

How it looks

Check before watering: push a finger into the mix (extension guides suggest 2.5–5 cm, 1–2 in, down) or lift the pot; dry mix is noticeably lighter. Top watering pours water over the mix until it runs from the drainage holes. Bottom watering stands the pot in a few centimetres of water until moisture wicks up, then removes it.

Signs

Underwatering: wilting, dry, light pot, mix pulling away from the sides, grey-green leaves, crisp edges. Overwatering: yellowing or dropping leaves, wilting with wet mix, soft brown roots, fungus gnats. Wilting can mean either, so always check the mix.

What favours it

Water needs change with species, light, temperature, humidity, pot size and material, and mix. Plants use much less water when growth slows (cooler or darker seasons, after moving to lower light).

Prevention

  • Check the mix every time; water only when the top layer has dried for most foliage plants.
  • Water thoroughly so the whole root ball is wet, until water drains from the holes.
  • Empty saucers and outer pots after watering; Virginia Cooperative Extension says not to leave a pot standing in water for more than an hour.
  • Use room-temperature water, not cold.
  • Bottom water plants whose mix has become hard to wet or whose leaves should stay dry (such as African violets); Virginia Cooperative Extension suggests 15–30 minutes in 5–7.5 cm (2–3 in) of water.

Treatment

Start with the first step and move down only if the problem persists.

  1. For a very dry, shrunken root ball, soak the pot from below until the mix rewets.
  2. For waterlogged plants, let the mix dry, check the roots and repot into fresh, free-draining mix if roots are rotten.
  3. Every 4–6 months, leach salts by running at least twice the pot's volume of water through the mix.

Pros and cons

Pros

  • Thorough, less frequent watering wets the whole root zone and flushes salts.
  • Bottom watering evenly rewets dry mix and keeps leaves dry.

Cons

  • Bottom watering alone does not flush salts; combine it with occasional top watering.
  • Fixed watering schedules ignore changes in weather and growth and are a common cause of overwatering.

Look-alikes

Overwatering
Wet, heavy mix with yellowing and wilting points to overwatering.
Underwatering
Dry, light mix with wilting or crisp leaves points to underwatering.
Root rot
Wilting that does not recover after watering, with dark soft roots, suggests root rot.

Typical uses

All container plants.

Sources

  1. Watering Indoor Plants — University of Maryland Extension
  2. Watering — Houseplants, University of Illinois Extension
  3. Properly Watering Container Houseplants — Virginia Cooperative Extension
  4. Houseplant Care — University of Wisconsin–Madison Extension

Written in our own words from these sources. Check a product label before using any treatment.