Protecting Trees in the New Normal of Summer Drought
(See this and other posts about City Park in our Arboretum Blog)
It finally rained, but this summer has really been one of extraordinary drought, which has been the case during several of the last five summers.
If you are planting new trees on a property as we are in the City Park Arboretum in Belfast, sequential years of drought are bad news for these new transplants…and all trees, really.
At City Park we have put in 17 new trees over the last 5 years, most in the last 2 years, thanks to a Canopy Grant from the Maine Forest Service. These trees are 6 to 10 ft tall and an inch to 3 inches in diameter. They are carefully chosen specimens of different species planted both for beauty and for education.
As you can imagine, trees of this size are not inexpensive to purchase or plant. The possibility of losing these new transplants in a drought like this is very significant, and so our staff and volunteers spend hours each week watering them. I have a water tank that sits on the back of my truck and gravity feeds water to each tree through a hose. It's still fairly slow process but better than hauling water in buckets.
Watering trees at City Park in Belfast
When you plant a tree you really need to account for the time and effort it will take to water it. With what seems to be our new normal, very dry summers with a lot of heat, expect to water trees every week for several years after you plant them. A good rule of thumb is 6 gallons a week per inch of trunk diameter. But you have to consider the type of tree and its water needs as well. It may rain a little but not the amount actually needed by these trees, so it's important to keep track of rainfall.
In general, if you don't water plants right after transplanting they're not going to make it. I like to water twice a week for 2 weeks after planting, then once a week for the rest of the season through October. A deep watering once a week is better than more frequent quick watering. But if it's extremely hot, twice a week during those periods is a good idea. If it's 95° and sunny, a tree is transpiring and taking up a lot of moisture and will be stressed if there isn't moisture at the roots for it to take up.
Even established trees can be stressed by drought, and drought combined with other stresses such as insect defoliation can add up to death or decline. If you have a large tree that is important to you, you can water the area under its crown, laying out a drip hose or a sprinkler for 8 hours or more.