Sultry late summer

August is usually one of the hottest months of the year – making watering essential. Try to use grey water wherever possible, especially as water butts may be running low if it has been a dry summer. August is traditionally holiday-time, so you might need to enlist the help of friends and family to look after the garden while you are away. When you are at home, take the time to prune Wisteria and summer-flowering shrubs such as lavender once they’ve finished flowering.

Prune Wisteria

Wisteria needs regular pruning to keep the growth and size under control, but it will also improve the flowering display.

Don’t delay summer pruning fruits trained as restricted forms

Summer pruning is mainly for apples and pears trained as restricted forms. It will allow sunlight to ripen the fruit and ensure good cropping for the following year.

Deadhead flowering plants regularly

Remove spent flowers as soon as they look scruffy – thankfully, a few days delay won’t make a difference. The simplest method is to just pinch off the faded blooms with finger and thumb.

Watering

Watering is key to growing plants well, so here we look at how to get it just right. This not only means providing the water our gardens need, but using it wisely. Water is a precious resource and supplies in the UK are under pressure from the effects of climate change, population increase and the need to protect the environment, such as river levels for wildlife.

When to water

Water in the mornings, if you can, as this is when the sun comes up and plants will start to use water. The foliage and soil surface is also likely to stay drier for longer than evening watering, discouraging slugs, snails and mildew diseases. Plants start to transpire in sunlight, drawing water from the soil, through their roots, up their stems and out through tiny pores on their leaves called stomata. Evening watering is also fine, as the cooler conditions mean less water is lost to evaporation. 

Watering in the heat of the day is not a good idea as much water is lost through evaporation from the surface of the soil and the plants will use water more efficiently if watered in the cooler parts of the day.

Watering frequency

We’re frequently advised to ‘keep plants well watered’ but just how often should that be and how do we know if a plant is getting enough water?

There is no simple rule of thumb for watering as each plant has different needs – for example, a container plant in hot sunny weather may need watering daily, whereas a mature shrub might only need a drink in extreme drought. But ​below are some things to think about and look for to help you get it right for your plants. It’s good to remember, plants will use more water if more water is made available to them, so you can allow them to dry out a little between watering and they don’t need to be wet all the time. 

Factors that affect how often you need to water:

• Size, species and stage of growth of the plant – the larger and more leaves a plant has, the more water it is likely to lose and the more nutrients are needed to grow flowers and fruit. These are mainly taken up through the roots, dissolved in water, so more water is generally needed to produce flowers and fruit
• Texture, structure and compaction of the soil or growing media and its organic matter content. Plants cannot extract every drop of water from soil and some soils may still feel damp even though plants have started to wilt. This tends to happen in clay soil. A clay soil can hold more water than a sandy one but plants are able to extract more water from sand than clay. In contrast, sandy soil can feel dry even though there may be moisture still available to plant roots. Sandy soils tend to need smaller amounts of more frequent watering than clay. Caring for your soil by adding organic matter will improve its water holding capacity
• Whether the plant is growing in a border or container or with root restriction e.g. next to a wall. A large plant in a small pot will need more frequent watering than one planted in a border. In a border, the roots are free to grow wherever they are able to find water and hence draw moisture from a much larger volume of soil than if the roots are confined in a pot. Plants that are potbound (i.e. have more roots than compost in the pot) dry out particularly quickly
• Season and weather (e.g. rainfall, hours of sunshine, temperature, wind and humidity) will affect the rate of water use. Generally speaking, plants use more more water in the warmer summer months and less in the cooler winter months. They will also use more in hot, sunny and windy weather. And watering will need to be more frequent during prolonged dry spells with no decent rain (light showers are of little use to plants as the water simply evaporates or only wets the very surface of the soil where there are few roots)

Signs that your plants may need more frequent watering

• Less than expected growth of foliage, or production of fruit or flowers
• Leaves or stems that look dull or lost their shine, sometimes darker or paler than normal
• Change in position of leaves, they may angle downwards or start to curl
• Wilting (take care though as this can also indicate overwatering!)
• Pots become lighter in weight
• Pots blowing over in the wind

If the surface of the soil or compost is dry, that does not necessarily mean that the plant needs water. Water is needed at the root tips, so surface moisture is not always a good indicator. If using the touch test, push your finger down into the compost or soil to at least knuckle depth to see if it is damp, rather than just feeling the surface.

How to water

Plants can only effectively use water through their roots, taking water from the surrounding soil or compost. So water needs to get to where it’s needed, at the tip of the roots and not the leaves. Wet or humid foliage will encourage fungal problems and evaporation from the surfaces.

Watering more thoroughly, but less frequently helps get the water down to the deeper root tips. It is better to water the garden before drought really sets in, to keep the soil moisture levels even and avoid the soil being continuously dry. But, equally important, the soil doesn’t have to be really wet all the time because plants roots need air as well as water to grow well. Consider the way we drink a glass of water, it doesn’t have to be full all the time, but we might prefer it was topped up half way rather than it becoming completely empty.

Where plant roots are restricted for example in containers or growing next to a wall or fence post, more frequent watering may be needed as the roots are extracting water from a smaller volume of soil than if they were growing freely in the border soil.