The art of watering

Imagine for a moment that you are parched with thirst. Would a teaspoon of water quench that thirst? Or a tablespoon? Or would you need at least a full glass? Chances are that it will be the latter and yet often we do not apply the same principle to plants – especially edible plants. Under-watering can be as detrimental as over-watering, and both are a waste of water. A plant, like us, needs to be adequately hydrated to stay alive but also it needs to be hydrated so it can transport nutrients (particularly calcium) to the whole of its being, and to thrive sufficiently to produce the edible parts: leaves and stems, fruit and flowers, roots and seeds.

Plants take in most of their water through their roots. A very tiny percentage is absorbed by leaves. In fact, leaves are designed to release water through transpiration. This means that there needs to be adequate water in the root zone, and that means deep watering. If you are unsure how deeply water is penetrating, then dig down and check. You will get used to how much water your plants need over time. Also, when you pull your spent plants out, check how long the roots are. This will give you an indicator for next season about the depth to which you need to water. Remember that without water in the root zone, plants cannot absorb nutrients.

Watering directly onto the soil with a hose, watering can or drip line works best for plants. It targets where the water goes and prevents water getting onto the leaves which results in mildew and fungal diseases. It also works best for us as we will not waste water by watering areas that don’t need it including paths, and this will reduce our water bills. Use a soft spray so that soil does not splash up onto lower leaves, bringing with it spores that are destructive to the health of the plant e.g rust on mints, septoria on tomato leaves.

Factors that need to be taken into count in deciding how much to water:

• stage of growth – bigger plants need more water than seedlings or smaller plants
• the weather – plants in high temperatures need more water than in lower temperatures
• the rainfall – rainfall of less than 10mm per day does not count
• how moisture retentive the soil is
• whether the plants are in full sun, partial sun or partial shade

When an extreme heat event is upon us, we need to begin hydrating our plants days beforehand (at least 3 days). It is too late once our plants have wilted. They may appear to recover but will have suffered permanent damage even if it is not visible to the naked eye. A well hydrated plant will not scorch or wilt. The fruit may burn however, just as we burn without sunscreen, so protect the fruit with shade cloth or even fabric or a beach umbrella for the duration of the heatwave, and water each morning or evening to top up the earlier watering.

*This is a short excerpt from ‘The Art of Watering’ workshop run by Robin Gale-Baker.

Written by Robin Gale-Baker