Water is the single most important nutrient that your gardens need to keep them beautiful and healthy. However, when it comes to watering, there are no hard or fast rules. If you water too much, the roots suffocate or rot. If you water too little, the roots dry up and die. Most of your decisions are judgment calls because it depends on the plant, time of day, amount of rainfall you get and time of year. How often you water also depends on the type of soil that you have, such as clay or sand.
Clay soil presents a bit more of a watering challenge because it has an electrical charge that draws water away from plant roots. There is little room for channels that allow an exchange of gases with the air above the ground and it can drain more slowly. You can determine how well the soil is draining by digging a two inch hole in various parts of the property and see how long it takes to recede. In order to deeply water clay soil, you may have to water, then wait a couple of hours and water again.
In contrast, sandy soil drains water more quickly. You can tell if you have sandy soil if the ground seldom puddles, even after a heavy rainfall. If the soil is too sandy, water may leach out too quickly and the nutrients are lost. A sandy soil will replace the water with air more quickly and hence, the reason why sandy soils dry out faster than clay soils. Although sandy soils need more water, more fertilizer, more amending and more mulch, they are much easier to work with and many plants prefer this type of soil.
Different types of plants require varying amounts of water, but as a general rule, flowering plants need about one inch per week. Annuals that are planted in the beds will need extra water as they become established, but after they are growing and flowering, the one inch rule applies.
Since annuals tend to have shallow root systems, and they spend almost their entire life blooming repeatedly, they need extra care. That, of course, depends on how the soil is draining and how much competition for water they are receiving from nearby plants. First thing in the morning is usually the best time to water garden plants so that the plants have time to dry off. If that isn’t possible, water in the early evening. Also, slower watering is more efficient. You should apply water directly to the soil instead of over the plants to avoid the spread of disease.
Flowering plants in containers will need more water since they will dry out more quickly than those planted in the ground. If the soil feels dry two to three inches below the surface, it’s time to water again since they too have a shallow root system. Containers generally need water every day. Add mulch to the container to help retain the moisture.
Trees & Shrubs:
Trees and shrubs have a deeper, more extensive root system and different water requirements. Trees and shrubs need moist (not thoroughly wet) soil in order to grow well, resist insects, reduce winter injury or produce flowers and fruit. The soil surrounding the plant’s “root zone” serves as a storage tank from which the plant draws moisture and nutrients. Most trees and shrubs shed rain water to the “drip line,” much like an umbrella. The most active water absorption area is at the drip line and beyond. This is where you should water. Most of the roots spread 1 ½ to 4 times as wide as the plant’s canopy. If trees are in the lawn, water them separately from the grass.
Even for an experienced gardener, knowing when and how much to water a garden can be a challenge. With a bit of knowledge, good climate that cooperates and the right watering techniques, your garden, trees and shrubs will look healthy and vibrant all season long.