I have been working in the landscape industry now for more than 25 years and have the history books of a 92 year old nursery at my disposal, and I can honestly tell you that fall is consistently my favorite time of year to plant. As the days get shorter, plants start the process of slowing or stopping their growth as they prepare for dormant season (winter). Most trees and shrubs take to transplanting quite well as dormancy approaches. As fall approaches nighttime temperatures start to go down; the combination of cool nights and warm ground encourages root growth in most species.
Plant's water needs start to diminish as we get deeper into the fall season. This year however, as we approach fall, we have locally dry conditions that are causing stress to new plantings as well as established plantings. As of the writing of this post, it's been well over a month since our last significant rain fall event. Despite the fact that we had a very rainy spring and early summer, it seems that the faucet was turned off in mid-August. You may notice established trees changing fall color a little sooner than normal or even dropping leaves prematurely. My 25 year old Crimson King Maple at home has dropped about 10% of its leaves already as a result of this late summer dry spell and above average warmth.
"So what should I do about it, Matt?" Well, I'm glad you asked.If your trees, regardless of age, are showing some stress (premature fall color, premature leaf drop, etc.) it is not too late to help them out. The way that we water an established tree differs greatly from how we recommend watering a newly planted tree, so pay close attention to the following instructions:
Watering and Caring for an Established Tree
An established tree is a tree that has been in the ground for three years or more. If a tree hasn’t been recently transplanted, it should have an extensive root system. My experience has shown me that many established tree root systems extend well beyond the drip line and can often be twice as wide as the tree canopy itself. The feeder roots for trees are the smaller finer roots out towards the end of the root system. In order to effectively water a tree, you have to get water to those feeder roots. An oscillating sprinkler placed in the lawn or bed directly under neat the dripline or just outside of the dripline is my preferred method for watering established trees. Leave the sprinkler to run for 2 hours per location. It is important to let the sprinkler run for an extended period of time in order to deliver water down to where the tree’s roots are. Based on the tree's size and the coverage area of your sprinkler, it may be necessary to move the sprinkler around the circumference of the tree's drip line in order to effectively hydrate the tree. This is a very effective watering method and can be repeated once every 2-3 weeks or until regular rainfall occurs. Bonus Tree Care Tip: adding a granular organic fertilizer such as Espoma's Tree Tone or Plant Tone would be a great idea at this time of year and would add beneficial organics back into the soil. These organic fertilizers are not high in water soluble nitrogen and therefore won't cause late season tip growth as most chemical fertilizers would do if applied at this time of year. These recommendations can be applied to established shrub beds as well.
Watering and Caring for a Newly Planted Tree
As stated above, trees need water delivered to wherever the feeder roots for a tree are located. In the case of newly planted trees (trees that were transplanted this year or in the last 2-3 seasons) the root system may actually be narrower than the canopy of the tree. Sprinklers or lawn irrigation systems are not effective at getting water to the root system of newly planted trees. My preferred method is to water the tree with a slow trickling hose placed right next to the trunk of the tree (in the mulch ring). Typically I tell people to turn the hose on about a quarter turn and let it trickle at the base of the tree for 30-45 minutes. This method will hydrate the root ball and the surrounding soil that contains the tree's root system. I recommend doing this type of water once every 7-10 days for your younger trees. It is important to let a tree dry out a bit in between waterings. This drying out period will encourage the roots to go deep and will help prevent root rot diseases which are more prevalent in our heavier soils than they are in parts of the country that have sandy or loose soils. If you had a tree that was just planted by our crew, water it according to the above instructions for 30 minutes the same day the tree was planted and again about 3 days later. After the first week you can start to follow the above recommendation of just once every 7-10 days.
Watering & Caring for a Newly Planted Shrub
Newly planted shrubs need to be watered once every 3-5 days. Placing a slow trickling hose at the base of the shrub and letting it run for 3-5 minutes is sufficient. Considering the above average heat and dry conditions - water your shrubs each day for the first 3 days and then start following the above recommendation of once every 3-5 days. Larger (10-gallon or balled & burlapped) shrubs can be watered on the same schedule but increase to 10-15 minutes with the slow trickling hose.
Written by Matt Zerby, President of Wasco Nursery & Garden Center Thursday, September 22, 2017 (c) 2017 Wasco Nursery, Inc. - all rights reserved