There are no exact rules for watering plants. Water newly planted trees at the time of planting, and then adjust all watering according to the plant's needs. Since different plants have different moisture requirements, soil and plant conditions should be used as the primary rule.
Most trees and shrubs in Oklahoma reach maximum growth when they receive the equivalent of at least one inch of water from rainfall or irrigation per week during the growing season. Newly planted trees and shrubs will need to be monitored on a daily basis
- Do not water until plants show signs of light wilting. Apply water slowly to allow it to soak into the soil. A TreeGator bag watering tool can help you with this. It holds 20 gallons of water and drips water exactly where you need it over a 4-hour period.
- Wet the soil to a depth of 12 inches. This encourages a uniform root system which is better able to withstand disease.
- Do not over water, since over watering can leach nutrients from the soil or deplete oxygen availability to the roots.
- Do not plant high moisture sensitive plants next to gutter downspouts or other areas where excessively wet soils may develop.
- Give special attention to plants set close to a wall where an overhanging roof may block rainfall.
- Check the soil level near the root zone and not just at the surface before deciding whether or not to irrigate. Quick summer showers may not supply enough moisture to wet the entire area around the root ball. To determine if you need to water, pull back the mulch and dig down 4"- 6" beside the root ball and check the moisture level. Use a long skinny screw driver to push into the root ball to get an idea of the moisture level.
- Lastly, mulch plants whenever possible to reduce supplemental irrigation as this also insulates the plant from freezing temperatures.
Plants benefit from winter irrigation when temperatures rise above freezing. For typical Oklahoma winters, this could be a significant portion of the season. This is particularly true for all broad-leaf evergreens and many deciduous species. When plants are properly mulched, the need for winter irrigation is greatly reduced.
How do I tell if a plant has been under watered or overwatered?
For the most part, if a plant starts to die from the top-down/outside-in with dry crunchy leaves, this is a sign of not enough water. These plants usually look good at the bottom where the water makes it up only so far. Under watering is easier to fix if caught in the early stages than overwatering because all you have to do is water; preferably with fish emulsion around the base to give new energy to push out new growth. This observation pretty much works with everything; although some plants like Sky Pencil hollies are not very forgiving about running out of water. It's harder for them to bounce back.
The signs for overwatering are usually leaves turning yellow with moisture still in them beginning from the lower portion of the plant and starting from the inside out. The tops are the last thing to look bad because they are getting the right amount of water to the top of the tree. Planting a tree too deep will also cause these symptoms. Overwatering is a lot harder to fix! To help keep from overwatering try the following: pull away mulch from around the trunk; turn sprinklers away from the plant; and of course, stop watering and let the ground dry out. If it looks like rain while waiting for the plant to dry out, then it’s a good idea to use fish emulsion around the tree and let the rain "water it in" to help push out new growth when it does dries out.
There are a few trees and plants that are hard to overwater. They include: Bald Cypress, River Birch and Weeping Willow trees.