Do we really know how to water a tree?
10.06.2021 – ENGLISH
In the first two to three years newly planted trees need some help to get enough water. When lifting a tree always losses a small part of the roots, which means that the tree temporarily has less roots available at its new location. Also, the roots do not go further than the root ball, so it has fewer options to extract water and nutrients from the soil. Because of that it is very important to keep the root ball moist to prevent the tree or shrub from drying out.
How much water does a tree need?
A tree needs water from the moment it gets its leaves. It is often asked how much water a tree needs, but fixed amounts cannot be given. It all depends on the weather conditions, the type of tree, the size that has been planted and the site conditions. Watering trees is custom work and sometimes it is difficult to assess. When you are having doubts if you need to give extra water, it is wise to check the moisture of the root ball. This can be done, for example, by digging a narrow hole right next to the root ball or by putting a gouge into the root ball.
How often do you need to water trees?
If the tree needs water, give a good amount of water at once, instead of a little every day. It is important that the water reaches the entire root ball and not only the top layer. Water the trees maximum once a week, depending on the weather. Let the soil dry a little before you water again, so that the roots are stimulated to look for water by themselves and start to grow outside the root ball. However, never let the soil dry out completely. Keep the root ball moist, but don’t water too much! If the site is continuously soaked, the roots will rot, eventually causing the tree to die.
Watering trees: watch the video
Noud de Jong, sales advisor for the UK market, explains in this video how you can provide trees with water. Colleague Niels van den Elzen demonstrates the different methods.
How does the water reach the entire root ball?
The easiest way to ensure that the water ends up in the root ball is to make a barrier around the trunk. This barrier needs to have the diameter of the root ball. It can be made of soil, but there are also plastic and biodegradable trims available.
What also works well for trees with a root ball up to 8o cm diameter, is the use of a bucket with a little hole at the bottom. When you place the bucket, filled with water on the root ball, the water will seep out slowly and will be absorbed well by the soil.
Water bags do much the same, but over a longer period of time. The water is released very slowly by a seam at the bottom and it slowly sinks into the ground, prevent the root ball from drying out. In the summer, the water bags have to be filled on average once a week. By connecting several bags together, larger trees can also be properly supplied with water. When there are several trees together in a planting area, the use of a drip hose can be practical. This system also works very well for hedges. You can operate drip hoses manually, but there are also systems available with a timer. There are also moisture retainers such as Bio Lite Net, a biodegradable net that is put around the root ball before planting. This net absorbs water when the ground is wet and releases the water again when the soil gets dry.
What if the leaf starts hanging?
Sometimes it happens that the leaf, despite all the good care, starts hanging during a warm period. If the root ball is kept moist, it will not help to give more water. There is a limit to the capacity of the roots and it has probably been reached at that time. The heat causes the leaves to evaporate more water than the roots can supply. Pruning is often the best solution in such situations. It reduces the leaf mass and restores the balance. That may seem like a pity, but we know from tests that this gives the best results. After a few years pruned trees show a more beautiful, fuller appearance than trees that have not been pruned after planting. Click here to read more about pruning trees.
What else does a tree need?
In addition to water, roots also need oxygen and too little oxygen in the soil can also cause serious growth problems. Healthy soil life ensures the oxygen in the ground, but sometimes that underground life has been reduced or even disappeared. Often due to ground works. Tree technicians can measure the oxygen content in the soil, but you can always make a number of holes around the root ball for the supply of extra oxygen. In addition, soil life can be stimulated by mixing an organic soil improver through the soil around the root ball.
Van Den Berk – Watering trees: a practical guide