Advice
Watering during summer
Most of the water used by plants goes to replenish that lost by the closable pores, called stomata, that are present on the undersides of leaves. When the plant is flush with water stomata open allowing in air containing carbon dioxide. During photosynthesis sunlight powers the reaction of water and carbon dioxide to make sugars which are the energy source and building blocks used to make plants.
As the plant runs short of water the stomata close stopping photosynthesis leading to slower growth, and failure of the flower buds to form and fruit to develop.
Watering lets the plant keep stomata open when soil water levels diminish, allowing continuing growth and development.
As a rule-of-thumb 1 sq m (1 sq yd) of vegetation requires the equivalent of about 25mm (1in) of rainfall every five to 10 days, from the soil, rainfall or watering.
Applying
too little water will only wet the upper layers of the soil
where there are few roots and may actually encourage the plants
to keep their roots in these areas which are especially prone
to drying out and resulting in less drought resistance.
In summer, plants use more water than falls as rain. Therefore plant growth at this time of year depends on reserves of water in the soil, left from the winter surplus, topped up by rainfall or watering.
When to water
Inspecting the soil at a depth of 30cm (1ft) can provide guidance. If the soil feels damp there is unlikely to be any need to water, but if it is dry, then watering is probably required for some plants. Not watering some plants can delay maturity and can usefully spread the harvest period or season of interest. Gardeners should be aware that clay feels damp even when all available water has been used and sand can feel dry even if some water is available. Only experience in matching the observed state of an individual soil to the growth rate of the plants can help gardeners fine tune their watering.
Excess water will run to waste below the root depth, so before watering check the weather forecast and wait to see whether topping up the rainfall is needed.
Watering guide
Water whenever the soil seems dry |
Water every 10- 14 days in dry periods |
Never water |
Perfect lawns |
Many plants in drought-prone sandy soils or the stickiest clay |
Everyday lawns, wild flower meadows, rough grass |
Leafy salads, Peas and beans in flower |
Most fruit and vegetables |
Large fruit trees and currant bushes, carrots, parsnips and herbs** |
Newly planted subjects |
Moisture-loving perennials* |
Most perennial borders and ornamental grasses** |
Containers and hanging baskets |
Bedding plants |
Drought-resistant succulent plants |
Areas beside high walls |
Most established, perennial plants in deep fine sandy soils, good quality loams or clay loams. |
*More water needed on sandy soils.
** On poor soils, water every 10- 14 days in dry periods, though this is not required on good soils.
Applying water
Good watering aims to apply enough water to replenish the soil, without overdoing it, at a steady, gentle rate. You should apply water only at the stem bases beneath the foliage canopy leaving the surrounding soil dry. This limits weed problems and ensures all water goes to where it does good.
Sprinklers:
Sprinklers have a limited use in gardens, such as
watering lawns where essential and raising the moisture level
of unplanted areas.
Hose pipes: Large droplets and jets of water damage soil surface. This leads to water running away from where it is needed. Fine sands and silts are especially prone to packing under the impact of water. A lance or trigger device controls the flow putting the water gently where it is needed.
Ponding: Ponding, using earth banks, allows water to soak in. Alternatively, some plants can be grown in trenches that can be filled with water.
Leaving hoses trickling beside plants is ineffective as the water goes straight down rather than spreading out around the area where roots congregate.
Buried pipes: Putting in pipes to direct water to the roots are ineffective as they do not lead to a wide area of wetted soil for the plants to root into.
Bucket:
Buckets are quick to fill and empty but have similar
disadvantages to hosepipes.
Watering can: Without a rose watering cans behave like hoses but are a lot more work! With a rose there is less danger of soil damage, run off or saturation. However, the rate of flow is very slow and it is laborious to water a large area thoroughly.
Seep or drip hoses: Water seeps slowly from these and sinks into the soil. In coarse textured soils there is little sideways movement of the water and more emitters or nozzles are needed.