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Underwatering

Also known as Drought stress, Dry soil

DiseaseHarmful
Wilting hydrangea leaves — wilting with dry soil is the first sign of thirst Photo: Jules Verne Times Two · CC BY-SA 4.0

In short

Underwatering happens when a plant's potting mix dries out further or for longer than the plant can tolerate. It shows as wilting, curling and crisp brown edges, and chronic drying can kill a plant. It is usually easy to reverse if caught before the roots dry out completely.

How it looks

Leaves droop or wilt and may curl; edges and tips turn brown, dry and crisp. Older leaves at the base of a dry plant often yellow and fall first. Flowers and buds drop quickly. The pot feels light, the mix is dry several centimetres down and may shrink away from the sides of the pot.

Signs

Wilting that recovers after watering; crispy brown leaf tips and margins; leaf curling; yellowing and dropping of the oldest leaves; flowers fading or dropping early; dry, shrunken potting mix.

What favours it

Irregular watering, hot or bright positions and strong sun, and small pots packed with roots all make a plant dry out faster. Mix that has dried out hard can shrink from the pot sides and shed water instead of soaking it up.

Prevention

  • Check the mix before watering rather than watering on a fixed calendar, and water more often in hot, bright or growing periods.
  • Water thoroughly until water runs from the drainage holes, then empty the saucer.
  • Group moisture-loving plants away from heat sources and strong direct sun.

Treatment

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

  1. Water thoroughly until water drains out of the bottom of the pot.
  2. If the mix has shrunk from the pot sides, water it several times in succession until it is fully re-wetted and water drains from the bottom.
  3. Trim fully dead, crisp leaves; partly damaged leaves will not turn green again but can stay on the plant.
  4. Do not feed a stressed plant until it has recovered and is growing again.

Pros and cons

Cons

  • Repeated drying kills root tips and weakens the plant.
  • Brown edges and dropped leaves do not recover.

Look-alikes

Overwatering
Overwatered plants also wilt, but the mix is wet and the pot heavy.
Low humidity damage
Dry air also browns tips, but the mix is moist and the plant does not wilt.
Salt and fertilizer burn
Salt damage browns tips and margins with a white crust on the mix or pot, despite regular watering.
Sunburn
Sun scorch affects only the most exposed leaves as bleached then brown patches.

Affected plants

All potted plants; succulents and cacti tolerate dry spells far better than leafy tropical plants.

Sources

  1. How to help a poorly houseplant — RHS
  2. Houseplant Diseases & Disorders — Clemson HGIC
  3. Houseplant Problems — UC Statewide IPM Program
  4. Overwatered Indoor Plants — University of Maryland Extension

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