Parks and Recreation

Water New Trees the Right Way
Typically, Iowa springs are wet, but what happens when they are dry? What does this mean for our plants? It is likely that we will see less fungal disease this year. Fungi need water, and rainfall has not only been low, but very sporadic. By the time we did get some rain, the leaves of many plants were maturing and less susceptible to fungal infection. That does not mean we will see no fungal diseases, just less of them. Some fungal diseases may still crop up because we tend to wet the leaves of our plants when we water them, and that can start a fungal infection. Also, we did have some rain, and it may have come at the right time and kept the plant wet enough to get fungal problems started.

So, that brings us to the topic of watering. We do need to consider watering our trees, shrubs and gardens? Some people are not watering at all. Why? Because we are not used to spring being dry and we are not in the habit of thinking about watering until the heat of summer. When we do water, we need to do it right.

Here are some things that are done wrong on a regular basis and a way to do them right:

  • Watering plants every day. Containers may need to be watered every day. Almost nothing else does. Newly planted plants need to be checked every day, but generally don’t need to be watered every time they are checked. We check new plants daily to see if the soil is moist or dry so we can decide if we need to water or not. When the soil is drying a bit, then be sure to water thoroughly so we are getting water to the whole root system. Shallow watering leads to weak, shallow root systems.
  • Using the watering device wrong. There are a lot of good devices for watering, but if they are not used right, they don’t give us good results. Know how to use the device you choose for watering.
    • Soaker hoses are great because they keep the leaves dry and deliver water right to the soil. Unfortunately, many people don’t run them long enough. Often, they get run for about 15 minutes or so. Soaker hoses deliver water very slowly and they may need to be run for an hour or two to really do the job. Run the 10 hose for an hour and then dig a little hole. If the soil is not moist 5 to 6 inches deep, you need to run it longer.
    • Root feeders, with their long needles are great because you can stick them in the soil and go do something else. You just need to move them around from time to time to get good coverage of the root system. The holes that deliver the water are at the lower end of the needle and often the needle gets inserted into the soil too deep. Even most big trees have their roots in the top 18-24 inches. If you plunge that needle into the soil deeply, you are missing a lot of the root system. Insert it so that the tip of the needle is only 4 to 6 inches deep. That will put it into a very active part of the root zone.
    • Lawn sprinklers/in-ground irrigation systems are handy because they cover a large area and you can do other things while they are working. Like soaker hoses, these often get run for only 15 minutes or so and the result is the same. Not watering deeply enough. We would like to apply an inch of water when we do water. We are not getting that after 15 minutes. Next time you turn on the lawn sprinkler put out a soup or tuna can and see how long it takes to get 1 inch. I think you will be surprised.
    • Irrigation bags are great for newly planted trees and shrubs. Fill the bag and the water comes out slowly through the bottom of the bag. Also, the water comes out and goes right into the root ball, exactly where we want it. Some people want to fill the bag every day. These bags are not meant to be full all the time. Fill them every 5 to 7 days. I know of one case where the new tree died because the owner filled the bag every day and rotted the tree.
  • Assuming that mature trees don’t need water. Even mature trees can benefit from watering. Lots of people assume that trees have roots that go down several feet. Most trees, even large mature ones, have the majority of their roots in the top 18 to 24 inches. While that is better than the root system under your perennials, the tree roots need to supply water to a very large organism. They have wide-spreading root systems to get enough water to sustain the tree. If some of the roots are in dry soil, they are not contributing to the water supply, and that tree is not going to get as much water as it should. That means the tree is under stress.

Watering can be expensive, but it can also be an investment in the future of your trees and shrubs. Watering a tree not only sustains it for today, it helps it produce a full canopy of leaves next spring. Mid-summer is the time when many of our trees produce buds that will open into leaves in spring. If there is not enough water, the trees may set a smaller number of buds or the buds may not develop as well as they should. That could impact how well the tree leafs out next year.

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