Watering plants and gardens during hot, dry weather requires careful timing, as watering in the heat of the day is largely ineffective. The Royal Horticultural Society (RHS) explains that much of the water evaporates before reaching the roots, making early morning the optimal time to water.
Why daytime watering fails
As Britain endures successive heatwaves, over two-thirds of England and all of Wales have been declared in drought status, prompting nine water companies to implement hosepipe bans, also known as Temporary Use Bans. Gardeners are urged to take preventative measures to protect their plants from the severe conditions.
Watering vegetation in direct sunlight during the warmest hours proves ineffective because the majority of water evaporates before penetrating to the roots. Plants cannot absorb the necessary moisture through this approach, providing minimal benefit.
Best times to water
RHS guidance states: "Watering early in the morning is the best time. There will be less evaporation, and plants can use the water through the day." Evening watering is also acceptable, but the RHS cautions: "Evening watering is acceptable, but damp leaves overnight can encourage pests and fungal diseases."
Stuart Thompson, senior lecturer in plant biochemistry at the University of Westminster, speaking to Gardens Illustrated, notes that plants tend to consume their own body weight in water during a hot, sunny day. He adds that plants outside pots and planters benefit most from morning or evening watering, allowing water to permeate the soil and nourish roots.
Deep watering for drought-tolerant plants
The RHS offers a tip to transform plants into 'drought athletes': "Deep, occasional watering encourages deep roots and drought-tolerant plants. Train your plants to be 'drought athletes.'"
Matt J Adams, founder and lead gardener at The Relentless Gardener, advises for reviving yellowing lawns: "Water smarter, not harder. A thorough soak every few days is much more beneficial than a light sprinkle every evening. Deep watering encourages the roots to grow further into the soil, making the lawn better equipped to cope with the next dry spell. Water early in the morning or later in the evening to minimise evaporation and avoid scorching the grass."
