by Nancy Penrose
With summer on its way, and after the difficult times we’ve all been through as a result of the coronavirus pandemic, people are beginning to turn their attention again outdoors. Caring for our lawns, gardens and trees naturally brings a bit of much needed enjoyment. There has never been a better representation of regrowth and rejuvenation than the time-honored tradition of planting a tree.
So it leads to the question: “Can I really plant a tree successfully in summer?” Traditionally in the Pacific Northwest, planting trees is done in Fall, Winter or Spring, because the trees are more dormant during this time. However, planting in summer can be done, provided the tree is consistently irrigated and monitored.
Planting Trees in Summer
The danger with planting a tree in summer is that when you plant a tree, at any time, it puts a lot of stress on the tree. Your new tree is in an unfamiliar environment and hasn’t established its roots to the extent that a mature tree has.
When trees are first planted, they need a lot more water than mature trees. For the first 2 years you should be prepared with an automated watering system.
In summer, trees need enough water to make it through the season, but also to ensure their roots are built up with enough strength to survive the cold of winter. You will need to watch the trees carefully to ensure they are getting enough water, but not so much that the roots get flooded.
Proper watering practices are vital to the survival of a newly planted tree. Watering trees sounds simple enough. Surprisingly, it’s not that easy given that new trees die in the landscape from lack of water every year. The most common cause of decline in newly planted trees is improper irrigation. Here’s the secret: Get water slowly to the root ball to ensure slow delivery so water can gradually soak into the root-ball. Forget sprinkler irrigation, and especially rainfall. Oftentimes, people start up their irrigation systems too late in the season assuming the rain is sufficient. Rainfall WILL NOT water your newly planted tree effectively. Remember, newly planted trees must live entirely off the moisture in their root-ball until roots grow away to surrounding soils. Give them a chance.
Newly planted trees should be irrigated with automated drip irrigation for TWO COMPLETE GROWING SEASONS. This is typically April through October. Water for 15 minutes every day the first year, and 30 minutes 3 days a week the second year. Drip irrigation uses the least amount of water with the highest efficiency. It evenly distributes water directly over the rootball of newly installed trees and it provides consistent moisture levels. Regular pop up sprinkler heads WILL NOT water your newly planted tree effectively, nor will “diligent” hand watering.
Irrigation amount and frequency are dependent on:
Season, Air Temperature, Soil Texture, Soil Structure and Tree Species
With so many factors it is difficult to give an irrigation standard that is appropriate for all trees and landscapes. Generally, no irrigation is needed when trees are dormant. The period of dormancy for deciduous trees is easy to determine because they lose their leaves. Evergreens go dormant also. Use deciduous trees as indicators for the dormancy period for both types of trees. Irrigation should begin when deciduous trees start to bud up or leaf out in early spring. The most amount of water will be required mid to late summer when soil moisture has been reduced and air temperatures are at their highest. In mid to late fall the irrigation schedule can be tapered off back to a watering schedule that was used in early spring. Once fall leaf drop occurs discontinue watering until the next growing season.
So how do you know if you have achieved the right irrigation frequency and timing? One simple method that gives good results requires some investigation:
Use a trowel to dig down at the root zone approximately 4-6”. Pick up a small handful of soil and squeeze it tightly in the palm of your hand. If the soil has formed slightly to the shape of your palm after you have opened your fist, the soil moisture is ideal. If the soil easily crumbles and falls apart the moisture level is too low, and if you are able to squeeze water from the soil when it is in your fist the soil is too wet. All water should be absorbed within 6 hours, and no puddling should occur in the root zone.
Trees absorb both oxygen and water from the soil. Overly saturated soils have little available oxygen and soils that are too dry hold any moisture so tightly that it is unavailable to trees. It is a fine balance that requires continued monitoring and adjustments.
Mulch to Conserve Soil Moisture
Mulch should be used to help conserve soil moisture, and you should replenish the mulch often enough. Bare soil can heat up too much in summer, as water will evaporate quickly. You should generally lay down a couple inches of mulch at a distance about 1 foot from the base of the trunk. Your tree should have a layer of mulch around it all year-long, but in summer this is critical.
Inspect For Tree Health
Keep an eye on your trees to ensure they are remaining strong. If leaves or branches are damaged, they can be pruned. If you notice or suspect any signs of damage or a disease, you can always call a specialist to do an inspection and see what the trouble is. Remedying this quickly could mean the difference between whether the tree will be able to thrive, or not.
With enough care and attention, you can ensure your trees survive the summer and continue to be a beautiful addition to your yard for years to come.
Nancy Penrose is the owner of Big Trees Inc., located in Snohomish, WA in the Seattle area. The company is one of the largest tree nurseries in the Seattle area with over 120,000 trees available in over 300 varieties. They not only deliver young trees, but also mature trees in a wide range of sizes. Some types of trees available include spring flowering, deciduous, evergreen, and privacy trees. The company also does tree transplanting including large trees. Their blog can be seen at https://www.bigtreesupply.com/blog/ or https://arboristblog.com/. They can be reached at 360-563-2700.