When Warm Becomes Too Hot: Understanding Optimal Water Temperature For Healthy Plant Growth

Watering plants in hot weather can be challenging, and it is important to understand how your plants absorb and process water to ensure they stay healthy. While all plants need water to survive, the timing and amount of water are crucial. The general rule is to water early in the morning or late in the evening, avoiding the peak of the day when water is more likely to evaporate before the plants can absorb it. Watering at the right time of day ensures that a higher proportion of water is used by the plants and helps them prepare for hotter weather.

Water pot plants in the morning or evening

Watering your pot plants in the morning or evening is a great way to ensure they get the hydration they need without putting them at risk of disease.

The morning is the best time to water your plants. This is because temperatures are usually cooler, which gives your plants time to absorb the water so they can get through a hot day. Watering in the morning also means any excess moisture on the leaves will dry off quickly, reducing the risk of diseases taking hold. If you water in the evening, be mindful of watering more directly at the roots rather than the leaves, as the foliage can sit damp overnight, which can attract fungal diseases.

If you water in the afternoon, the best time is late afternoon or early evening. The temperature will have started to drop, and there will still be enough sun to aid in water evaporation. However, be aware that if you water your plants too late in the day, their leaves may not be able to dry off as quickly as they would at other times, leaving them susceptible to disease.

The worst time to water your plants is at the peak of the day, when the sun is at its hottest. Not only is it unpleasant to be outside at this time, but watering your plants can also be harmful to them. Watering at midday leads to rapid evaporation, reducing the amount of water that reaches the roots. Water droplets on the leaves can also act as tiny magnifying glasses, which can cause leaf scorch.

Watering twice a day – once in the morning and once in the late afternoon or early evening – is recommended for plants in containers, especially during hot weather. Pots dry out much faster than plants in the ground, and smaller containers will need watering twice a day during hot weather.

Avoid watering at midday

Watering your plants at midday is not ideal for a few reasons. Firstly, it's the hottest part of the day, and you don't want to be out in the worst of the sun, potentially having to carry heavy watering cans.

The main issue with midday watering, however, is that it is the least efficient time to water your plants. This is because the rapid evaporation that occurs in the heat of the day reduces the amount of water that reaches the roots. Watering early in the morning or late in the evening is preferable, as the plants will have more time to absorb the water.

If you water in the middle of the day, the water is more likely to evaporate before it can benefit your plants. This is especially true for young plants and those grown in pots, which can dry out extremely quickly.

Another issue with midday watering is that water droplets on leaves can act as tiny magnifying glasses, potentially leading to leaf scorch. This can be avoided by always watering the base of the plants and avoiding getting the foliage wet.

Finally, watering in the evening can be risky as the foliage can remain damp overnight, potentially attracting fungal diseases.

Don't overwater

Overwatering your plants can be just as harmful as underwatering them. It can cause multiple problems for plants, including root rot and stunted growth, and make them more susceptible to pests and fungal diseases. Here are some tips to avoid overwatering your plants:

• Check the soil moisture level before watering. Use your finger to check the moisture a few inches below the surface. If the soil is still damp, wait another day or two before watering again. Alternatively, use a moisture meter to check the soil moisture content.
• Avoid overcompensating during hot weather. It can be tempting to think that your plants need extra water in hot weather, but this can be damaging. Stick to your regular watering schedule and adjust as needed based on soil moisture levels.
• Water your plants thoroughly, but not too frequently. It is generally better to water your plants deeply and less frequently. This encourages stronger root growth and helps the plant become more resilient to dry conditions.
• Ensure proper drainage. This is especially important for potted plants, as insufficient drainage can lead to waterlogging. Make sure your pots have drainage holes and periodically check that they are not blocked.
• Pay attention to the type of plant. Different plants have different water needs. For example, plants from tropical regions with large leaves, such as philodendrons, typically require more water than desert plants like cacti and succulents.
• Be mindful of the time of day you water. Watering in the morning or evening is best, as it gives the water a chance to be absorbed before the heat of the day causes it to evaporate. Watering at midday can lead to rapid evaporation and leaf scorch.
• Observe your plants for signs of overwatering. These signs can include wilting or yellowing leaves, stunted growth, leaf drop, and the presence of fungus gnats. If you notice any of these issues, ease up on the watering and allow the soil to dry out slightly between waterings.

Check moisture levels

Checking moisture levels is critical for growing plants successfully. While it is important to water your plants regularly, overwatering can be as bad as underwatering, and both are common mistakes that can kill plants. The key is to learn how to gauge soil moisture effectively and water your plants only when they need it, rather than on a set schedule.

The simplest way to check moisture levels is to use your fingers to feel the soil. As a general rule, a potted plant in a container measuring 6 inches (15 cm) in diameter needs water when the top 2 inches (5 cm) of soil feels dry to the touch. For a larger container measuring 8 to 10 inches (20-25 cm) in diameter, the top 0.5 to 1 inch (1.25-2.5 cm) of soil should be dry. You can also use a trowel or a wooden dowel to determine the depth of soil moisture. If the dowel comes out clean, the soil is dry; if it's damp, the soil will cling to the dowel. In most cases, the soil should be damp to the root zone, 6 to 12 inches (15-30 cm) deep. However, sandy soil drains quickly and should be watered when the soil is dry to a depth of 2 to 4 inches (5-10 cm).

Another way to check moisture levels is to use a soil moisture meter, a simple and affordable device that can help you avoid overwatering and underwatering. These meters typically indicate soil moisture on a scale of 1 to 10, with 1 being completely dry and 10 being very wet. Analog meters use a colour-coded scale, while digital meters usually show a number. You can find soil moisture meters suitable for both indoor and outdoor plants at garden centres and nurseries, as well as online. When using a moisture meter, insert the probe into the soil as deep as possible without hitting the bottom of the pot. Wipe the probe clean and wait a few minutes before taking a reading. If the meter shows that the soil is still slightly moist, moisture-loving plants like Bird of Paradise or Palms should be watered. If the soil is completely dry, plants like Snake plants, ZZ plants, and Succulents need to be watered.

It's important to check moisture levels regularly, especially for potted plants, as they require more water than plants in the ground. Monitor their moisture levels frequently and adjust your watering schedule to prevent the soil from drying out completely. During hot weather, it's recommended to water potted plants twice a day to ensure they are getting enough moisture, as soil in pots dries out much quicker.

Water from the bottom up

Watering your plants from the bottom up, or bottom watering, is a great way to ensure your plants are getting enough water without overwatering them. This method is especially useful for plants that are sensitive to having water splashed on their leaves, such as African violets, snake plants, and philodendrons.

To bottom water your plants, you'll need a tray or container with no drainage holes, and a larger container to hold the tray and water. The tray should be large enough to accommodate your plant's pot and have enough space for a few inches of water. You can use a sink, bathtub, or a large container like a rubber tub.

Here's a step-by-step guide to bottom watering:

• Check if your plants need watering. A good indication is to stick your finger about an inch into the soil. If it feels dry, it's time to water.
• Pour water into the bottom of your tray or container. The amount of water will depend on the size of your pots. For smaller pots (6-8 inches in diameter), add about 1.5 to 2 inches of water. For larger pots (10-14 inches in diameter), add about 3 inches.
• Place your pots in the tray or container of water. If your pots are lightweight and tend to float, wet the soil from the top first to give them some weight.
• Let the pots soak in the water for 10 to 20 minutes. Check the moisture level of the soil after 10 minutes. If the water has been absorbed, add more.
• Once the plants have been bottom watered, remove them from the tray and place them in another tray or container to drain any excess water. This should take about 10 to 15 minutes.

Bottom watering is an effective way to water your plants, ensuring consistent and even hydration. It also helps prevent over and underwatering and reduces the mess and splashing associated with traditional watering methods. However, remember to occasionally water your plants from the top to flush out any excess mineral or salt buildup in the soil.

Frequently asked questions