The watering requirements of trees, shrubs, and grasses are directly related to local weather and soil conditions. It is important to understand that over-watering can be just as stressful to plants as under-watering. The failure of plants to survive or thrive in the first few months is almost always due to under- or over-watering. Please use the following guide to help you determine the best watering program for your landscape.
The ideal way to water most trees is to provide a slow, constant amount of water. A hose placed at the base of the tree and turned on low works well. The amount of time you should water your tree in this manner will depend upon its age and size. The goal is to soak the soil surrounding the tree's root system. For newly planted trees, 5 to 15 minutes will usually suffice. For balled and burlapped (B&B) trees. 30 minutes or more may be necessary. If your tree is too far from a water source, a bucket with a hole in the bottom will work. If trees are watered this way, they need to be watered every third day or so (more often in excessive heat or drought). Once trees are established, one watering per week should be sufficient when the weather stays very hot and dry.
Exceptions: There are exceptions to this method of watering. Dogwoods and Japanese maples, for example, prefer more frequent, shallow watering designed to moisten only the top several inches of soil above their roots.
Most newly planted shrubs should be watered at least every 3rd day for the first few weeks. One to five minutes per shrub, depending on its size, should be sufficient. Keep the water pressure fairly low so that water can seep into the ground without running along the surface away from the plant's roots. Newly planted material should be watered directly at the base of the plant, as if it were still in a container. This will assure that water reaches the roots. Once a shrub has been in the ground for several weeks and shows no signs of stress, this technique is less important, and you can start watering with a sprinkler. However, this direct base watering technique is much more efficient during critical watering periods such as droughts.
Once shrubs are established, water the equivalent of 1" per week if rainfall has not met this amount.
Exceptions: As with trees, some shrubs, such as rhododendron, azaleas, and pieris, prefer more frequent, shallow watering when planted in well-amended soils.
Lawns, too, should be watered deeply. For newly seeded or sodded lawns, thorough early morning watering is best. An inch of water per week is what is needed. Once you start watering in the summer, maintain a regular schedule- a hit-or miss approach can be worse than no watering at all. Fescue does prefer to go dormant during hot, dry summers and it can survive for several weeks without water.
The watering requirements of these plants can vary significantly from plant to plant. For this reason, it is important that you inquire about your plants’ watering needs when you purchase them. Some planning will also help-such as grouping plants with similar water requirements-in preventing problems before they start.
Overwatering (or excessive rainfall) can create several problems. Among these are “drowning” (reduction of the oxygen available to root systems) and encouragement of fungal development. Unfortunately, overwatering can produce symptoms like drooping, wilting, or browning leaves that mimic the symptoms of under watering. In such cases, we tend to water even more, compounding the problem. Dogwood and rhododendron are prime examples of plants that react this way. If you feel you are providing enough water to your trees and shrubs, yet they look like they need more, you should consider this problem as a possibility. If you have an automatic irrigation system, you need to pay close attention to potential overwatering.
Summer & Winter
Vacations are the primary summer threat, especially to newly-installed plants. As little as one day of hot, dry weather without watering can determine whether newly planted material will survive. If possible, have a friend or neighbor tend your plants while you are away. While our local winter weather is unpredictable, we often experience cold and windy days that can dry plants out as quickly as hot summer days. In non-freezing temperatures, trees and shrubs planted in the fall need to be watered throughout the winter months (particularly evergreens). The watering requirements described above, though, can usually be cut in half.
Much Ado About Mulch
Never underestimate the value of a layer of mulch around the bases of all your plants - annuals, perennials, shrubs, and trees. Mulch prevents the intense rays of the sun from baking the soil, keeping it loose and easy for water to penetrate. Mulch also cuts down on much of the evaporation from the soil, "holding in" the water you are adding while giving you some weed control to boot.
If you have any questions or concerns, please contact David Lepro at (717) 701-5797.