When it comes to the long term health of plants, the first couple of months are the most important. Aside from proper planting, which you can learn in our How-to videos, proper watering leads to quick establishment and fast growth.
Both trees and perennials follow the 3-2-1 Method that I created years ago, but in different units or amounts and different time frames: trees are watered by gallons and months while container-grown perennials use 20-ounce soda bottles and weeks.
Just to be clear, the “3-2-1” actually refers to the frequency of watering over the course of weeks or months.
Let’s begin, shall we.
Water amounts are determined by tree caliper or diameter. We use 1-2 gallons per 1 inch of tree caliper (or thickness). But most trees are sold by containers, so how do we determine the caliper? In general, 5-gallon and 10-gallon tree containers will be 1-1 ½ inches caliper and 15-gallon and 20-gallon trees will be 2 inches thick. Keep in mind the SAWS WaterSaver coupon minimum tree size is a 5-gallon container.
Using a 5-gallon container tree that has a 1-inch trunk, at planting we’d water the tree — in the absence of rainfall — 1 gallon of water per watering event three times a week for a total of 3 gallons per week.
So, the 3 of the 3-2-1 method means we water for the next month 3 times a week, 1 gallon per event for a total of 3 gallons. The next month we water two times a week, but each event is half the previous month’s total. In our example, it would be 1 ½ gallon per event or a total of 3 gallons per week.
Finally, during last month we water 3 gallons of water once a week for one month.
We are attempting to follow the important axiom of all plant establishment, whether grass or tree, water lightly and frequent, changing to deeply and infrequently.
The process is exactly the same except the amount or unit we use is a 20 ounce soda bottle and the duration is in weeks.
1st three weeks – three times a week, one 20-ounce for a total of 60 ounces or ½ gallon.
2nd two weeks – two times a week, one and one half 20-ounce soda bottles each time for a total of 60 ounces or ½ gallon.
3rd and final week – once a week, three 20-ounce soda bottles or 60 ounces total water.
Why offer such a formula?
Most people don’t know how to water properly or determine the correct amounts. The key is frequent, small amounts. Initially, oxygen for root growth is more important than water.
Most people drown their plants in the false hope of making their plants grow faster when in fact it’s the opposite. Another misconception is that watering outside the root ball to make the roots grow outward and deeper. You can’t make roots grow with water, but you can waste water trying to do so.
The key to all plant establishment, and therefore long term health, is consistency. Consistency with water and consistency with pruners. Ah, but that’s another story at another time…
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About our expert
Mark A. Peterson is a conservation project coordinator for San Antonio Water System. With over 30 years of experience as an urban forester and arborist, Mark is probably the only person you know who actually prunes trees for fun. When not expounding on the benefits of trees and limited lawns, you’re likely to find him hiking San Antonio’s wilderness parks or expounding on the virtues of geography and history to his friends.
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