Expert advice for watering your garden in a heatwave – and it’s less often
Watering at the right time can make the difference between a heat-tolerant garden and a water-stressed garden in a matter of days
Heat waves put both plants and those who care for them to the test. Temperatures are rising and the sun is setting for hours in this first heat wave of the summer, which will last until Thursday, according to AEMET. One of the most frequently asked questions among gardening enthusiasts and experts is what is the best time to water plants so they can get the most out of them.
While it may seem like it’s always good as long as the soil is dry, the truth is that the chosen time of day has a direct impact on the roots’ ability to absorb water, the evaporation of water, and even the overall health of the plants. Therefore, experts agree on a recommendation that is especially important during periods of extreme heat.
The Royal Horticultural Society (RHS) says early morning is the best time to water plants as there is less evaporation. When the sun has not yet reached its peak intensity, temperatures are milder, water has more time to penetrate the soil before evaporating, and plants can use the moisture throughout the day.
Additionally, watering in the morning ensures that plants have sufficient water reserves to cope with the hottest parts of the day. Throughout the day, leaves lose water through transpiration, a natural process accelerated by high temperatures. The plant can better withstand heat stress if the roots have sufficient moisture.
Another benefit is that it allows excess moisture in the leaves and stems time to dry before nightfall, reducing the risk of fungal infections and other diseases. The next best option is to water in the late afternoon or dusk when temperatures begin to cool. Meanwhile, evaporation slows down again and water remains in the soil longer.
However, some experts recommend that the leaves should not be left wet overnight, especially in areas with high ambient humidity. That’s why they recommend directing water directly to the base of the plant, where it’s actually needed.
What seems obvious is that midday is the least suitable time for watering. In extreme temperatures, a significant portion of water is lost before it reaches the roots, resulting in wasted resources and less effective irrigation.
Little and frequent watering error
During a heatwave, many people choose to water small amounts several times a day. But experts often recommend a different strategy: deeper, less frequent watering. Once water penetrates a few centimeters into the soil, roots are forced to grow into deeper, moister areas. This strengthens the plant and makes it more resistant to periods of drought or high temperatures.
The RHS says Shallow watering can leave roots closer to the surface where the soil dries fastest. Use the ‘finger test’ to find out if you need water again. It involves sticking a finger a few centimeters into the soil. If the soil is still moist, the plant probably doesn’t need any more water. If it is dry, it is time to water again.
Not all plants respond to heat the same way. Those in pots, planters or hanging baskets tend to suffer more during periods of high temperatures.
The reason is simple: The soil volume to store water is less and the roots warm up more quickly. In these cases, it may be necessary to water more frequently, always checking the condition of the compost first.
It is also helpful to group pots together in partially shaded areas during the hottest parts of the day to reduce moisture loss.
In addition to choosing the right time to water, there are other measures that will help preserve soil moisture for longer. One of the most effective ways is to apply a layer of mulch around the plants. Materials such as pine bark, dry leaves, compost or plant cuttings act as natural insulators, reducing evaporation and protecting roots from heat.
The RHS says established trees, shrubs and perennials growing in borders generally do not need regular watering, even in hot weather. Instead, priority should be given to newly planted specimens, vegetables, containers and hanging baskets.
It’s not enough to just water more during a heatwave; It is also important to irrigate more effectively. Avoiding watering in the early morning or evening hours allows plants to make better use of each liter of water and reduces losses through evaporation. Adopting more efficient watering habits not only helps to keep gardens and terraces in good condition, but also contributes to a more responsible use of an increasingly valuable resource.
Heatwave irrigation checklist
- Water early in the morning if possible.
- There is water at the base of the plant, not in its leaves
- Water deeply rather than little and often
- Check soil moisture before watering again
- Mulch exposed soil to reduce evaporation
- Pay more attention to flower pots and hanging baskets
- Avoid watering during the hottest hours of the day
