I know how it is, the day is nearly done and you haven’t got round to doing the watering yet. But you know that your plants are thirsty. You are wondering if plants drink water at night, and is it safe to do the watering during the night? What is the best time of day to do the watering?
Looking at nature always gives the clearest answer. It rains day and night so it’s ok to water day and night. There are some things to think about which will be explored further in the article below.
What actually happens when you water a plant?
First we need to start with the fundamentals. Whether you are watering outdoor plants, indoor plants or container plants, the same thing happens. Water falls onto the soil surface and is absorbed into the soil or growing medium. The water is stored here in the soil. As and when the plant needs it, water is absorbed through the root tissue by osmosis. Water is then available to the plant to assist in growth and development via photosynthesis.
Water flows up through internal pipes in the plant called xylem. A bit like our blood vessels but they carry water and dissolved nutrients not blood. The really interesting thing about water flowing up a plant is that it is the action of evaporation from the leaf surface that draws the water up through the xylem – nifty!
So why could it be bad to water at night?
And this is why many people think that watering at night is bad. Because the plant will not absorb so much water because there will be less evaporation from the leaves. At night the stomata close. However this misunderstands that watering is simply the act of adding water to the soil pore spaces, making it available to the plant WHEN THE PLANT IS READY.
It is then up to the plant to take up the water as and when it needs it. Our job is simply to have the right amount of water in the right place to be made available to the plant.
A key thing to bear in mind is that the root tips which are the very small end of the root are massively abundant in plants – this is why they sometimes look and feel hairy. They have a HUGE surface area so when they need to they can get enough water into all parts of the plant. If the plant needs less water it simply shuts down some of the stomata to reduce the evaporation, which then draws less water up from the roots.
What if there is too much water?
If there is excess water in the soil the plant will leave it where it is and only draw it up as and when necessary. This can of course cause problems if the soil is waterlogged. Roots will rot over time in soils that remain waterlogged. For example in pots that are not able to drain freely or ground that is flooded for a long period. In these cases it is actually the lack of air within the soil that is the problem that causes the rot. The pore spaces in the soil which should be half filled with air and half filled with water become totally filled with water. With no air spaces the roots start to rot.
What time of day do plants drink the most water?
So whilst watering can take place at any time, the rate of water uptake from the plant will be highest when the stomata are open. When daylight breaks in the early morning, the stomata will open and photosynthesis begins. This process will carry on through the middle of the day and into the evening. So the plant will actually take up water throughout the day according to the weather conditions – both heat and wind. In cooler temperatures the plant will take up less water. It is at this time that you can provide too much water, so always monitor your soil conditions carefully.
Can plants take in water at night?
During the night time plants will take in a little bit of water. It will be less than during the day time.
Do I need to water my plants every night?
In most cases no. Watering should take place when the soil or growing medium is starting to dry out. It is rare that a plant would have absorbed all of the water in a growing medium within 24 hours. However if it was exceptionally hot and windy then this might happen as water would be evaporating from the plant and the soil surface. On hot days always test before watering by sticking your finger into the soil to ascertain if there is moisture within the soil.
It can get confusing at times of hot weather when plants temporarily wilt during the day. In this case the rate of transpiration is higher than the rate at which the plant can take up water – even though it is available in the soil. It looks as though the plant is wilted and the caring plant parent thinks it needs more water. However this is not the case.
It is a good idea to observe your plants that have wilted on hot days during the night to see if they have recovered. This observation coupled with the soil finger moisture test will give you all you need to know whether or not to water.
What is the worst time to water a plant?
The heat of the day is the least optimal time to water. This is because of water conservation reasons. As a general rule of thumb water loss will be much higher during the heat of the day. In contrast to water loss from the surface of the soil in the late afternoon or late evening.
However imperfect action is far better than perfect inaction. If waiting until a good time means that the plant will not get watered, it is far better to water when you can!
Remember that for you the best time of the day is the time that you can take care of your plants. Mother nature does not wait for the perfect time, rain falls and sun shines and plants grow.
Whatever watering schedule you have, when dealing with young plants there is less leeway. Therefore it is more important to worry about watering them than the time of day. This approach will lead to happier plants which will grow into strong, healthy garden plants.
Do plants take up nutrients at night?
Plant roots absorb water via osmosis. There are minerals present in the soil, dissolved in soil water. These soluble minerals will also flow into the plant via osmosis in the same way as water. So in the same way as with water, they can take up some nutrients at night. They will take up more nutrients during the day.
How does the type of soil affect watering?
A free draining soil which is high in organic matter will be great for new plants whatever time of day the watering is done. Enabling their herbaceous root systems to get access to water without encouraging fungal growth. If your soil has a high clay content and water pools at the base of the plant add organic matter. This will improve the soil structure. A drainage hole can also be a good idea. Dug beside new plants will give the plants time to absorb the water, whilst excess drains away.
A sandy soil may dry out quickly and require more regular watering.
In conclusion the most important thing for healthy plant growth is frequent watering. At a rate that is suitable to the type of soil. Use your finger to test whether or not the soil needs to be watered. And always bear in mind how water is taken up by the soil to promote optimal root health. If in doubt, add organic matter!