Hopefully you watered your trees and shrubs when we had unseasonably warm Winter temperatures in February and March. As expected, now that Spring has arrived, so has the bitter cold and potential for snow. The cold temperatures will not harm your tree and any precipitation we may receive, snow or rain, will be very beneficial.
The Hose Method
When watering trees and shrubs place a hose with no nozzle next to the trunk of each individual tree and shrub and let the water run on a slow to medium flow until you're certain you've soaked the entire root zone. Depending on your flow and the size of the plant, this may take anywhere from five to thirty minutes. One of the advantages of planting container grown trees and shrubs is that the soil medium in the container is light which makes it easy for you to use a moisture meter. Moisture meters (sold at Tagawa Gardens) tell us immediately if the root zone is dry, moist or wet. They really do take a lot of the guess work out of properly watering your landscape. Keep in mind that it's alright to let the root zones of your trees and shrubs dry out a little between waterings. Trees and shrubs do not like to stay wet all the time.
Irrigation Systems
I think I have a bad impression of irrigation systems because by the time the homeowner asks me to get involved with their landscape many plants have died, either from way too much or way too little water provided by the irrigation system. Within the plant world we call them Irritation Systems. If designed and built properly irrigation systems are a thing of beauty. But if you don't inspect and adjust irrigation systems at least once per year they can be lethal to your plants.
Irritation System Maintenance/Adustment Tips
Keep in mind that different plants have different water requirments, especially if you're adding xeric or native plants to your landscape.
As plants mature, so do their root systems. You'll need to pull the drip lines/heads away from the base of the tree or shrub.
While running your irrigation system, test each zone by placing each drip head in a short pan or bucket to make sure each head is emitting the appropriate amount of water. Sometimes irrigation lines can get pinched or heads can get clogged and you don't know until the plant is dead.
How many gallons?
I don't know. Every plant is different. I've heard other tree professionals suggest that a recently planted tree needs 10 gallons of water per inch of trunk caliper every week. So a 2" caliper tree would need 20 gallons of water every week. I think in the heat of the summer that's probably pretty accurate. Using the 2" caliper tree as an example, I would split that amount into two waterings per week, 10 gallons per watering. I really don't think trees need that much water in early spring, fall or winter.
Different plants have different water needs and different soils drain quicker than others so it wouldn't be smart for me to recommend the same amount of water per plant for your entire landscape. This is where a moisture meter comes in very handy.
How often do I water?
Using the hose method for watering trees and shrubs, and a moisture meter, I've had great luck with the following guidlines:
January - water each tree and shrub once per month if the the temperatures stay above 40 degrees for more than a week
February - water once per month if temps are 40 degrees or higher, twice per month if temps are 50 degrees or higher
March - water once per week if temps are 70 degrees or higher, once every two weeks if temps are 60 degrees or below
April - water once per week if temps are 70 degrees or higher
May - water once per week if temps are 70 degrees or higher, twice per week if temps are 80 degrees or higher
June - water twice per week if temperature is consistantly 80 degrees or higher
July - water twice per week if temperature is consistantly 80 degrees or higher
August - water twice per week if temperature is 80 degrees or higher
September - water twice per week if temperature is 80 or higher, once per week if temperature is in the 70's
October - water once per week if temps are in the 70's, once every two weeks if temps are in the 60's
November - water once per month if temps are above 40, twice per month if temps remain above 50 degrees
December - water once per month when there is no snow on the ground
That wet area in your landscape ...
Wet areas in residential landscapes seem to be common. Typically it's caused by several neighbor's irrigation systems emptying into or flowing through one unlucky yard. If you have an area in your landscape that stays wet all the time you may have to select plants that can handle that type of wet environment. Shrubs that tolerate wet spots include a variety of Dogwoods, Elderberry and Willow. Trees that tolerate wet spots include Birch, Willow, Alder, Boxelder and Sycamore or London Planetree. The nursery professional at Tagawa Gardens can help you with these recommendations.
What about natural precipitation?
The "rule of thumb" is that if we get a solid 1" of rain you can skip watering for a week. I think if the temperatures are in the 60's or 70's that's probably accurate. If the temperatures are in the 80's and 90's I think we need to see at least 1.5" of rain to justify skipping tree and shrub watering. What about snow? Most weather forecasters suggest that, on average, it takes 10" of snow to equal 1" of moisture. I think the spring snows are heavier with moisture and it's not uncommon for 4" of spring snow to equal 1" of moisture.
General
If a tree or shrub dies within the first year of being planted it's often due to too much or too little water. Trying to figure out how much water your recently planted trees or shrubs need can be challenging. There are a number of environmental conditions that will determine how much water your plants need including air temperature, wind, soil texture and sun exposure. For example, if your tree is located in a windy area that gets sun all-day and your native soil is sandy, you will have to water your tree more than if the tree were planted in a shaded area, with no wind, and a clay soil. If you have an irrigation system in place with spray or drip heads that water each tree or shrub the mystery can get a little more complicated.
