Tips For Watering Trees And Shrubs
Learn where, when and how much to water your trees and shrubs to keep them growing and blooming in good health.
If you want healthy trees and shrubs, you need to understand their water needs so that you can take care of them properly. There are certain general rules that apply to all trees and shrubs, and other rules that apply to particular conditions and climates. If you take a careful look at your trees and shrubs you can decide which of these techniques apply to you.
Trees and shrubs are most at risk when they are newly planted, because their roots systems need time to grow and spread and adequate water is crucial to this growth. This is particularly true when they are planted in an area such as the land around a newly built house. The soil in such an area has probably been packed down by heavy machinery during the construction process, and topsoil may have been removed and water tables and natural drainage patterns disturbed. If you are landscaping your newly built house, make sure that the soil is prepared as well as possible for planting and that good regular watering is established to help the new plants develop a good root structure. Consult your local nursery or landscaper on recommendations for the types of plant you wish to grow, and follow their advice as closely as possible.
Then set up a good automatic watering system following the general guidelines below. If you are planting in an area that has not been disturbed by construction or heavy equipment, take a good look at existing growth. Patterns of current plant growth will tell you a lot about drainage, light levels and other conditions that will affect the health of your desired plantings. If the soil is barren, you may want to reconsider making a big investment in shrubs and trees and soil conditioning to plant there. If small plants are already doing well, larger plantings are more likely to succeed in the same area. Again, although you can hand water them, an automatic irrigation system is more reliable and will be very helpful during the period in which the trees and shrubs are establishing their new root systems. Remember that the larger the tree or shrub was when it was transplanted, the more water it will need to support itself and grow.
Once plantings are established, with good root systems, the other danger to trees and shrubs is periods of heat and drought. It’s important to learn good watering techniques, whether you water by hand or with an irrigation system. Here are a few important watering tips:
Water deeply and slowly so roots can absorb as much of the water as possible. The best time to water is early in the morning. If you water during the hot part of the day, as much as 50% of water evaporates. Spray is less effective than drip watering, because spray also tends to evaporate rather than sink into the soil. Water drops on leaves in sunlight can cause burning. Drought issues exist everywhere. If you are lucky enough to have regular rain throughout the hot part of the year, you may not need to water. However, most parts of the United States do have periods when it is important to supplement the natural supply.
To water the trees and shrubs properly it’s also important to understand how their absorption system works. The tree’s root system is vast. Its width may be as much as two or three times the height of the tree. The roots that absorb water most effectively are usually within the tree’s canopy drip line zone. This is the area within which water drips from the leaves, or which is in shade when the sun is directly overhead. If you have an irrigation system arrange it so that the water drips into a number of points in the canopy area. Set the timer to water deeply twice a week. If you are hand watering with a sprayer, use the coarsest spray you can. You can also use a soaker hose or ball. Whatever method you use, water slowly so that the water can penetrate as deeply as possible and the roots have the maximum opportunity to absorb the water. If runoff occurs, move the house to a new area. This means twice a week. More frequent watering will encourage trees to develop shallow roots. Shallow roots are particularly vulnerable to drought and to storms. A tree with shallow roots may blow over in heavy winds.
Deep watering encourages trees and shrubs to sink their roots deeper, which will help them to survive future droughts. Avoid poking holes in the ground under the tree. This is more likely to damage roots than to improve water absorption. In climates where there is a high water table or wet winters, shrubs and trees may not require watering until hot weather comes and the soil dries out. However, a hot climate increases the need for water. Pike Family Nurseries, an Alabama retail nursery, recommends the following water guidelines to its clients. Shrubs less than four feet in height require about a minute or five gallons of water. Larger shrubs that are taller than 4 feet require an additional fifteen seconds of watering for each foot of height. Thus, a shrub 8 feet tall requires 2 minutes of watering or ten gallons of water. Trees need 2 gallons of water for every inch of trunk diameter at your shoulder height.
In a northern climate like that of New England, you may only need to water during the summer, but when hot weather does come, make sure you have a watering schedule in place. If foliage wilts or curls, it may be drought stress. If you choose to plant trees and shrubs in the fall, water them well. Remember that all trees and shrubs need water throughout the fall until the ground freezes. Early fall color may also be a sign of stress due to drought. Wherever you live, make sure you plant varieties of trees and shrubs appropriate to your area. Climate zones only a few miles apart can vary drastically in how hot and dry they are. If you are just beginning to landscape, take a look at your neighbors’ plantings and see what is doing well for them.
Talk to local garden support services such as master gardeners’ groups or your local nursery, and make sure you select plants that are known to thrive in your area before you invest in young plants. Once you’ve selected your plants, or if you are caring for an existing garden or plantings, set up a regular schedule, ideally with the help of a timer and an irrigation system so that forgetfulness or a traffic jam don’t undermine the health of your large plants. Make sure that the watering elements are well placed under the canopy line of your trees or the shade of your shrubs. Water deeply and not too often, and watch your trees and shrubs flourish.
Author: Sarah Mandel
About Author: Sarah Mandel gardened professionally in the San Francisco Bay area and cares for her own garden in the hot dry summers of California’s Central Valley.