Pot Plants And Summer Heat: Watering Strategies For Survival

Pot plants require more frequent watering than plants in the ground, and this is especially true during hot weather. In fact, potted plants may need to be watered twice a day when it's hot.

The best time of day to water plants is early morning, or late evening. This is because watering in the middle of the day can cause rapid evaporation, reducing the amount of water that reaches the roots. Watering during the coolest parts of the day also gives plants a chance to absorb moisture before facing the heat.

Water early in the morning or late in the evening

Watering your plants in the early morning or late evening is crucial to their health and survival, especially in hot weather. Here are the reasons why:

Preventing Water Loss Through Evaporation

Watering early in the morning is ideal as it prepares your plants for the day ahead. The morning temperature is usually cooler, and your plants are in the best condition to absorb moisture from the soil. This is because the warm conditions during the day increase the rate of evapotranspiration, the process by which plants cool themselves with water. By watering early, you ensure that more water reaches the root system before it evaporates in the heat.

Avoiding Peak Sun Hours

Watering during the hottest part of the day is detrimental to your plants and should be avoided. Watering at midday when the sun is at its peak can lead to rapid evaporation, reducing the amount of water that reaches the roots. Additionally, water droplets on leaves can act as tiny magnifying glasses, causing leaf scorch.

Evening Watering as a Second Option

If you are unable to water your plants in the morning, late evening watering is the next best option. However, it is important to be mindful of a few things. First, do not oversaturate the plants if you are scheduling an evening watering. Second, keep the water off the plants' leaves to prevent fungal diseases. Leaves that remain wet for extended periods are more susceptible to fungal infections. Morning watering is preferable as it allows the plant to dry before nightfall.

Benefits of Evening Watering

While morning watering is ideal, there are some benefits to watering in the evening. The cooler evening temperatures mean that moisture won't evaporate as quickly, giving it more time to soak into the soil. This benefit is particularly important for vegetable gardens, which require deep watering at least two to three times a week, preferably in the mornings or evenings to keep the soil moist.

Avoid watering at midday

While it may be tempting to water your plants when you see them wilting in the midday sun, it is best to avoid doing so. Watering your plants at midday is not beneficial to you or your plants. Not only will you be exposing yourself to the worst of the sun's rays, but your plants will also suffer.

Firstly, watering in the heat of the day will lead to rapid evaporation, reducing the amount of water that reaches the roots. This is because the temperature is higher at midday, and water evaporates faster in intense heat. By watering in the morning or evening, you allow more water to reach the root system before it evaporates.

Secondly, water droplets on the leaves can act as tiny magnifying glasses, causing leaf scorch. This is because the droplets can focus the sun's rays onto the leaf surface, burning the leaves. However, this is mostly a concern for plants with hairy leaves, as the hairs can hold the droplets far enough away from the leaf for scorching to occur.

To avoid leaf scorch, direct the water to the base of the plants, aiming for the bottom rather than the foliage. This will also help prevent fungal diseases, as watering the leaves can leave them damp overnight, attracting fungi.

If you are unable to water your plants in the morning or evening, it is still better to water them at midday than not at all. If plants are deprived of water, they will suffer, and you may not be able to revive them. Therefore, if you see that your plants need water, it is essential to provide it as soon as possible, regardless of the time of day.

Water deeply and slowly

Watering your plants deeply and slowly is a crucial technique to master for their long-term health. This method ensures that water reaches the roots of the plants instead of lingering at the surface.

Deep watering encourages plants to develop strong root systems. This is because plants that receive frequent shallow watering will not bother to develop strong, deep roots. By only watering infrequently and slowly, you are training the roots to seek out water at lower levels, which promotes stability for the plant. This makes the plant more resilient to dry conditions and drought.

To water your plants deeply, you should water them with a gentle and steady stream. Fast-running water will simply slide off the top of the soil. Clay soil, in particular, is very slow at absorbing water, so be patient. A good way to water your plants deeply is to use a soaker hose, which allows you to slowly saturate the soil without creating puddles. You can also use drip irrigation, which is designed for deep watering.

The amount of water needed will depend on the type of soil you have. Sandy soil, for example, loses water to evaporation faster than clay soil. A good way to check if you have watered your plants enough is to dig a trowel about 4 inches into the soil and check the moisture level. If the soil is only a bit moist at 4 inches deep, you need to water again.

Deep watering is an effective way to ensure your plants are getting the water they need, and it will also save you time and money.

Move potted plants to the shade

Potted plants are particularly vulnerable to hot weather, as they will use up water very quickly. Moving them into the shade is a good way to reduce their heat exposure.

Firstly, it's important to choose the right plants for your potted display. Hardy perennial plants are ideal, as well as tender bedding plants like begonias, which can tolerate some shade. Perennials may cost a little more than one-hit bedding, but they can be moved into the garden once your potted display is past its best, so they offer good value for money in the long run.

When planting up your pots, half-fill them with multi-purpose compost with added organic matter or well-rotted leaf mould. Break up large lumps as you go to make sure no air pockets form. Mix in a measure of slow-release fertiliser to keep plants healthy and provide the nutrients they need for the growing season. Position the plants one at a time, taking care not to damage any flowers as you plant. Add the shorter plants, putting them close together so the display looks good straight away, and fill any gaps with compost.

Water your potted plants well initially to settle the compost around the roots, and then regularly to ensure the pot doesn't dry out. Frequent watering during hot summer months causes nutrients to leach out of the soil, so supplement with a water-soluble fertiliser every other week in midsummer.

When moving potted plants into the shade, be sure to choose a spot that is still bright enough for any sun-loving plants to flower. For example, plants like impatiens, fuchsias, and begonias will thrive in full to partial shade, while petunias, pansies, and violas need at least three hours of sunlight each day.

Check the soil moisture

Checking the moisture of the soil is crucial to understanding whether your potted plants need watering. Here are some ways to do this:

Visual Inspection

A quick glance at the surface of the soil can give you a general indication of its dryness. Moist soil is usually darker than dry soil, so when you see lighter brown-coloured soil, this indicates dryness. However, this method is more suitable for plants that should be kept moist, such as Umbrella Palms and Boston Ferns, and less so for drought-tolerant plants like cacti and succulents.

Finger Test

Sticking your finger into the soil is a simple and effective way to gauge soil moisture. This method works best for smaller potted plants, as you can reach 2-3 inches into the soil to feel how moist or dry it is. Be careful not to damage the roots; if you feel roots, try checking the moisture in another area of the pot.

Lift the Pot

Determining the weight of the pot is a common practice in nurseries. Water adds weight to the plant, so if it feels lighter than usual, it's probably time to water. For larger pots, try tilting them to get a sense of their weight. Regularly picking up your potted plants will help you recognise when they need watering.

Moisture Sensor

Using a moisture sensor is an easy and accurate way to check soil moisture levels. Place the probe about 3/4 of the way into the soil, and the sensor will indicate the moisture level, usually with a colour-coded system: red for dry soil, green for a good moisture level, and blue for overly wet soil.

Wooden Skewer or Chopstick

This low-tech method involves gently inserting a clean wooden skewer or chopstick into the soil and pushing it down to the bottom of the pot. If the skewer comes out clean, the soil is dry. If it's dirty, the soil is still moist or wet.

Other Signs

Once you've had a plant for a while, you'll be able to recognise when it needs water just by looking at it. Many plants will have droopy leaves and stems when they're thirsty. Succulents and cacti, for example, will go slightly soft and get wrinkled when they need a drink.

Frequently asked questions