How Much Should I Water My Trees in the Summer

August 8, 2018

You probably already know that the three most important rules for desirable real estate are location, location, location. Of course the curb appeal of beautiful, healthy trees in your landscape doesn’t hurt either. In that respect, the three rules of seasonal tree care are water, water, water. Either too little or too much water can leave your trees looking and performing poorly.

But how often should you water, and how much water is too much, or not enough? The answers depend on numerous factors based on the science of how trees grow, including healthy root systems, climate, soil type and condition, and weather extremes like heat and drought.

Specific watering needs also depend on the age and species of your trees. Mature trees in native habitats need less seasonal tree care than newer trees or exotic species. Well-established trees are able to tolerate moderate heat and dry periods much better.

Nursery species and newer transplants need more care and attention, especially in the first few weeks. Additionally, non-native or exotic trees require more attentive, seasonal tree care and should be checked often for any signs of water stress.

Newly Planted Trees

When purchasing nursery tree stock, you’ll find the roots are generally compacted in a tight ball of potting mixture, either wrapped and tied or planted in a large pot. No matter how your tree is packaged, take care not to damage roots when removing. Carefully follow all planting instructions provided with your tree.

After planting, it’s important to keep the root ball area moist until the roots have had a chance to spread out and grow further into the soil. Water the tree directly over the root ball every few days for the first weeks, and longer during warm weather.

If your soil has a large percentage of clay, it will leach moisture from the loam surrounding the root ball. In that case, you may have to water your newly placed trees daily. The goal is to keep the soil around the roots moist but not saturated, to a depth of approximately one-half to one-foot.

Once the roots have had several weeks to spread and grow, seasonal tree care becomes easier. Directing irrigation further out from the base of the tree, and watering to a sufficient depth on a weekly basis is generally sufficient.

Keep in mind that newly planted trees grow more quickly in the first few years than at any other time. Sufficient watering is important to support the early growth spurt. Pay particular attention to your seasonal tree care during this time and remember to monitor the moisture content of the soil around your trees during periods of unusual heat or drought.

Mature Trees

Once trees are well established, frequent watering becomes less necessary as roots grow well out beyond the drip line of the tree, forming a web of feeder roots beneath the surface soil. Mulching the ground around the base of your tree to several feet out from the trunk will help retain moisture for longer periods. Commercial wood chip mulch is a good choice.

Avoid watering close to the trunk of mature trees as too much moisture there encourages insect infestation or fungus.

Checking Soil Moisture

There are a few ways to check the moisture content of the soil around your trees. The easiest way is to try poking a knife, screwdriver, or other long tool into the soil. If it’s difficult to penetrate the soil, you need to water.

You can also check soil moisture by inserting the blade of a trowel into the ground near the tree and creating an opening large enough to poke your finger down into the dirt. If it feels warm and dry, it’s time to water.

If you feel you must get your hands into the soil to be sure, dig about six or eight inches down and scoop out a handful soil. It should feel cool to the touch. It should not be muddy or soaking wet, but rather easily rolled into a ball that holds its shape. If the soil is warm and crumbles in your hand then it needs water.

You can also purchase an inexpensive meter that will accurately measure the moisture content of your soil.

Under Watering or Over Watering

Goldilocks wanted a bed that felt just right. Who can blame her? Your trees want their soil beds to be just right too. Not too soft, not too hard, not too cold or too warm, and not too dry or too wet. It’s all about the roots and keeping them happy.

Signs of under watering in deciduous trees include dry, perhaps brittle leaves, curling or wilting, and browning, yellowing or scorching of leaves. Premature color change and leaf drop is another good indicator.

Evergreens will display yellowing or browning needles, while excessive leaf or needle drop, and die back of branches in both evergreen and deciduous trees also indicates lack of water.

If your trees are thirsty the solution is simple—step up your watering schedule, water to a depth of about a foot, and check soil moisture frequently to determine how often to water.

Signs of overwatering are spongy or soggy ground around the trees or ground that is constantly wet. New growth will often wither and die. It may appear lighter green. In cases of severe overwatering, leaves or needles may turn yellow. If leaves appear to be a healthy green, but break easily, you may be over watering.

Over watering is a common mistake in seasonal tree care. Overly moist or saturated ground for extended periods of time damages roots. Letting the ground become dry for short periods between watering allows for pockets of oxygen in the soil. Yes, your trees need to breathe too.

If you see water standing around your trees, or have noticed the signs of overwatering, there are a few solutions. You can’t turn off the rain, but you can turn off the hose; if you’ve been watering, stop. Also, assess your soil type. If it’s mostly clay, add compost to help drain the water away from drowning roots.

If you find water pools around your trees when it rains, do a little detective work. Find out where it’s coming from and whether it can be diverted by trenching or other means.

Trees are a long-term investment adding to the interest, beauty, and function of your landscape, so make sure to water with care.  

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