Best Time to Water Plants in Hot Weather

Blog
/ By Amanda

At the beginning of the gardening season, we open our windows and take a deep breath of new, spring air and slap on our gardening gloves. Spending hours in the garden never seems like a waste since we get beauty and food back from it, a reward for our labor. Then, the days get longer, and the sun gets hotter and we are unpleasantly surprised as our plants start to suffer and wilt, going from vibrant, happy green, to sad looking yellow. We have fertilized, we go out every afternoon and water, the plants get sunlight through the bright hours of the day, what has gone wrong?

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Just like humans and animals, plants have needs and times when it is best to fill those needs, as well as times when it is not going so helpful. Imagine feeding your dog five pounds of food in one day before you went away for a couple of days of vacation, thinking that he should be fine since he got all of his days of food at once. Everyone knows that that isn’t how it works! It is the same with plants; they need watering, fertilizing and sunshine, but only in the right amounts at the right times and you have come to the right place to learn what those times and amounts are!

When summer comes around and the temperatures begin to break records and the extreme weather starts to have an extreme effect on your plants, what do you do to salvage them?

Damaging Effects of Hot, Dry Weather

First, it is good to know why certain types of weather can really damage your plants, specifically hot, dry weather. This kind of weather will influence all parts of your plant, roots all the way to the leaves. Just like other living things, plants have chemical reactions that must take place for the right processes to happen to allow the plant to live and grow. Many of these reactions happen during photosynthesis, which is when a plant will convert sun and sugars into energy and send it to different parts of a plant for growth and maintenance. This is part of the reason for why water is so important to a plant, it uses water to carry nutrients throughout the plant to growing cells.

The heat affects the plant down to the soil by causing the soil temperature to increase. The hotter that the temperature gets, the more the processes of a plant, like photosynthesis and water usage and storage, will speed up. They will work faster and faster up to around 90 degrees Fahrenheit. Once the weather starts to hit above this limit, the plant either begins to shut down and go dormant to protect itself or will overextend itself and begin to die back. This means, though, that up to around 90 degrees Fahrenheit, a plant will normally be fine, with some exceptions of plants that are rated to low zones.

If the weather has been consistently hot, the temperature of the soil will increase. This can cause major damage to the shallow roots of a plant, meaning that plants that reach deep with taproots, like dandelions, will still be thriving as your beautiful grass lawn begins to go dormant and yellow. Plants that were growing in pots will also struggle because of the soil temperature as they don’t really have much of an option but to grow fairly shallow roots, so be sure to protect these potted beauties and set them in a shaded area to try and reduce the temperature that will build up in the soil. The symptoms of hot soil will be most obvious in wilting and foliage burn, so protect the temperature by mulching and appropriate watering, talked more about below.

Another stress factor for plants is the quicker evaporation that will begin to happen through the leaves of a plant. All plants have small pores, found mostly on the bottom of leaves, that the plant uses to “breath”, conduct gas exchange, as well as to “sweat” and stay cool, much like humans do. This method of using evaporation helps to cool the plants. The plants can open and close these pores, called stomata, but in heat they will often shut them down to attempt and reduce the amount of water loss a plant is experiencing. If they don’t shut down, and sometimes even if they do, the plant will lose vital amounts of water before it has the chance to use it in weather that is too hot and dry. The signs of this will often manifest first in wilted edges of older plant leaves, then the new growth at the tips will die back, and finally the whole plant will wilt and die. Desert plants have adapted to get around this, but most of our garden plants have not and will not be ready for the heat when it hits. It is up to you to help them prepare.

If you know that your climate often becomes very hot and dry, then it is a good idea to prepare your plants for this and fertilize them appropriately at the beginning of the season, as well as make mulch protections for them at a soil level. The fertilization will enable them to grow vigorously with strong stems and leaves instead of gangly things that will easily succumb to the harsh weather by wilting from any water loss.

Watering at Different Times of Day

For new gardeners, it can be quite difficult to know how much and when to water plants. This partially stems from the fact that there are no exact guidelines for each plant to know exactly how much is the perfect amount to promote maximum growth. Each plant will have slightly different needs. This means that while you are preparing and planning your garden, it is a good idea to make sure that the watering needs of many of your plants are similar. Most garden plants sold in greenhouses now will have similar needs as they are all being sold for gardens in the area that will be experiencing similar summer temperatures and soil types. This makes your job a bit easier.

Morning

There are many advocates for a good morning water, but there are definitely arguments going the other way as well. The positives of watering in the morning include the fact that it will give the plants a chance to soak up the water before the sun starts to scorch. If the sun has not yet come out, photosynthesis will not be happening at a very high level and this will give the water some time to sink in around the roots. However, many say that although the water is present before the sun is out, it will only have a chance to sink in at the shallower levels of the soil and will not encourage the roots to grow stronger and longer into the ground, which will protect them. They also say that this doesn’t give the plants enough time to take the water up, as well as begin to use it properly before the sun comes out and evaporation starts. Some also used to say that watering in the morning and getting the leaves wet will promote sun scald during the day. However, this was solidly disproved about ten years ago and does not need to be a worry when the sun is going to cause this water to evaporate from the leaves surface very quickly.

Midday

Midday during periods of hot, dry weather is undoubtedly the least beneficial when watering plants is being considered. All the negative aspects of watering during the morning are only exacerbated midday as the sun is already reaching its hottest point and the plants have already begun to shut down for the day. The water does not have any time to soak in before it has evaporated from the soil surface. When you come out in the evening, the ground will appear just as cracked and dry as it did before you watered it that day. Even the shallow roots of the plant will have very little time to absorb any of this moisture and it generally ends up going right through them without helping to protect or benefit the plant at all.

Evening

Watering plants in the evening can be great for them, done at the right time and in the right way. The biggest argument against watering plants in the evening is that getting water on leaves and stems that will sit there throughout the night can be a foster home to many different diseases. This is exactly what you don’t want to encourage as the plants are already being attacked by the sun! The supporters of watering in the evening, though, advocate for the idea since it gives the water much more time to really soak deep into the soil, thereby encouraging deeper root growth and helping to protect the plant from root damage. It also gives the plant more of a chance to start to take the water up and store it without “sweating” it right back out. This will also maximize the amount of photosynthesis that can be done earlier during the day before the sun starts to bake and will encourage the growth and healing needed to fend off the hot days.

The Answer

So, what exactly is the best practice for watering during the summer? Most have conceded that it is generally the best to water well in the early evening, before the sunlight is completely gone and just as the temperature starts to descend. This negates the harmful effects of water collecting on the leaves and stems of a plant as it will give them enough time to dry out with the remaining sunlight that will be available. It also gives the plant time to take up the water and begin to store it when it has all night to do it. Any water that hasn’t been taken up by the time the morning rays begin to hit will have gotten the opportunity to sink into the soil and the roots will begin to grow deeper. If you do decide to water in the morning, or this just fits your schedule better, then doing it early in the morning before the sun is out is going to be best for your plants.

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Considerations

Here are a couple of other things to consider when thinking about your garden and when and how to water it:

Soil Type

The type of soil that your yard is made up of will have a big impact on water uptake rates in your plants. The reason for this is that each type of soil will hold, or retain, water for varying amounts of time. The longer that the soil retains water that has gotten a chance to soak in, the more time the water is available for plant uptake. However, don’t let the pendulum swing too far the other way and allow your plants to drown.

If you don’t already know what kind of soil your garden is made up of, it is easy to test this. Many garden centers and outdoors stores will have small test kits that you might be able to do yourself, but it is also easy to get a rough idea without any extra tools. Go out into the area of your yard that your garden inhabits and dig out a little hole. Much of the time, the type of soil will change the farther down you go, so make an estimate as to where your plants roots might extend to, normally not farther than a foot for most annuals. Take some of the soil in your hand and try to roll it into a ball. If it rolls easily and quickly becomes a hard-packed ball, your soil is more clay; if it can’t roll into a ball or takes a lot of work, your soil has a high content of sand. If it seems to be in between these two results, there’s a good chance your soil is silty. Try to test a couple of different layers of soil from the top to the bottom as you dig down.

If your soil is more clayey, then be aware that water holds on to these finer particles more tightly so this soil type will hold on to the water longer. In this case, be sure to watch out for overwatering. Even in dry climates, water will be present for longer and the roots can end up drowning in your zeal to keep the plant perky.

The soils that contain more sand particles will tend towards drying out very quickly as they are bigger particles and allow more of the water to flow through. These soils will need to be watered with greater frequency as the plants will have much less of a chance to uptake the water before it gets too deep or evaporates away.

Finally, there are the silty soil gardens out there. Silty soil is a medium between the two previously mentioned types of soil as it has a higher water retention rate than sandy soils do while also having less of a chance of overwatering during dry weather.

Wind

Gardens are found just about everywhere in the world and in some areas, they seem to easily grow dense and beautiful while others foster much harsher conditions. One of these conditions that can hinder growth and water uptake is wind. If you live in a windy area, it is worth it to consider this in your watering routine. Wind of any kind will cause evaporation rates to go up. This means that as soon as the water leaves the hose and hits the soil, it has already begun to be whisked away. This will stop as much water from soaking down as far as it should go.

Plant Location Avoid Full Sun

One of the biggest assists that you can give your plants before they even have a chance to live and thrive in your garden is to choose a good place for them. Most plants bought from a garden outlet or store will come with a tag with it that specifies what type of sunlight it should get by amount during the day, full, medium or low. Pay attention to this. The less time during the day that a plant is directly in the sun, the less the soil and plant itself will heat up. Some plants require many hours of direct sunlight for prime photosynthesis rates, however, even these will want a bit of shade in the hottest hours of the day. Try to plant your garden, or even just specific plants, where they will be protected when the sun reaches its peak and you will find watering to be much less of a chore.

Tips and Tricks

Listed below are some great ways to help those who are just starting off with gardening to be able to figure out water needs and conserve water usage.

Tip #1: Use Mulch

Mentioned briefly in the sections above, using mulch around your garden plants can help to reduce the amount of evaporation from the top of the soil. Mulch can be almost anything, from hay, to old leaves, to wood chips and sliced tires. The type of mulch you use is up to you and what you might want aesthetically as well as the amount of water retention it will demonstrate. Some mulches, like hay or old leaves, might need to be changed out somewhat frequently so as not to get too wet too frequently and start to harbor diseases.

Tip #2: Water Deeply

When you water deeply it also enables you to water less frequently, a great thing for conservation of water and time! This means watering for long enough each time you do it, and concentrating on certain spots at a time, so the water is able to sink in. If you need to first get an idea of how long this is going to take, after you think you are done watering, dig into your garden soil a bit and see how far down the water has permeated. At first, you will be surprised by how much water it takes to really start to get down to the level it should!

Tip #3: The Tin Can Method

If you use an automated watering system or just turn a hose and sprinkler on for a while, then using this method can be a helpful gauge. For those of you with flat areas for gardens, this method generally works quite well. Make your own rain gauge by cleaning out a tuna can and setting it somewhere within the range that your water is set to hit. When the tuna can is filled up, this should mean that your garden has received enough water.

Tip #4: Use Native Plant Species

In some areas, water can be one of the most valuable commodities in the neighborhood. Green lawns and beautiful flowering gardens can be great, but if this comes at the cost of your water bill and local resources, some people may question if its worth it. One way some have found to get around this is to plant a garden with as many native species as they can. The reason this is often successful is because native plants will already be adapted and acclimated to the climate, ready for the hot, dry summers and not require as much water to still go through its normal life cycle.

Tip #5: Water Individual Plants with Bottles

Nobody likes the fallout plastic has on the environment, but if they are going to be used, here is one great way to recycle them. If your garden is mostly full of plants that have the same water needs, but some seem to be suffering more than others, use a bottle to keep water on them more often and meet their needs. To do this, dig down next to the plant, trying not to destroy established roots and hurt the plant farther. Cut the flat bottom of the bottle off and bury it nozzle first into the ground, tucking dirt around it to keep it in an upright, slightly slanted position so the water flows towards the roots. Then, when you are watering the rest of your garden, fill the bottle up and let the water gradually disperse down around the plant’s roots. The only thing to watch out for is to not swing the other way and begin to overwater, so just make sure the soil has a bit of time to dry out again before refilling the bottle.

There you have it, a guide to know why summers can be a bit stressful on a gardener and his plants, what might be necessary to maintain a beautiful yard during hot, dry weather, and tips for the best way to go about it. Good luck fellow gardeners!