“If fall is the best time to plant trees in Washington, why is Arbor Day celebrated in the spring?”

This question comes up often, so let’s break it down.

Arbor Day was founded by Nebraska farmer and statesman, J. Sterling Morton. The very first Arbor Day was celebrated in Nebraska on April, 10, 1872. In 1885, the Nebraska State Legislature recognized Arbor Day as an official state holiday to be annually observed on April 22, J. Sterling Morton’s birthday.

In 1957 the Washington State Legislature passed a law designating the official Washington State Arbor Day as the second Wednesday in April, which this year is April 11. Today, the national Arbor Day is commonly celebrated on the last Friday in April, which this year is April 27.

Scouts help plant trees in Poulsbo; a Tree City USA for 21 years.

So why spring? It is probably because, to an agriculturalist like Mr. Morton, spring is when farmers planted all of their crops. In their view, why should trees be any different?

Spring is the peak season for rainfall to naturally irrigate anything newly planted in states like Nebraska and many others throughout the eastern and central United States. Many of these states also receive periodic rains from summer thunderstorms that help trees get through the hottest months of the year.

It is also believed by some horticultural experts east of the Rockies that certain species of trees, including oaks, ginkgos, dogwoods, birches, hornbeams, and yellowwoods, among others, have lower mortality rates when planted in spring versus fall. Whether that thinking applies to Washington state, I can’t say that I know for sure…

What I do know is that our environmental conditions are a little different here.

East of the Cascades, communities receive anywhere from 8-20 inches per year, primarily between November and January. Pair this with prolonged periods of hot, dry weather in summer and I think you can see why planting trees in fall is preferred.

On the west side, our waterworks turn on in mid-September and don’t quit until early May. Our summers are mild but it rains almost never between June and August. Once again, these conditions point to fall as a better time to plant trees.

So why do most Tree City USA communities in Washington celebrate Arbor Day and plant trees in April? I’m assuming it is mostly tradition, but just because fall is preferred doesn’t mean that spring is off limits.

The most important thing is to properly mulch and water your trees for the first year after planting, and then at least through the summers for the next year or two following. If your tree gets enough water then it can survive and establish itself no matter when, or where you planted it.

Here are some additional links to thoughts on spring versus fall planting:

Iowa State University, Fall Planting of Trees and Shrubs

Oregon State University, Fall is Good Time to Plant or Move and Replant Perennials, Shrubs or Trees

Garden Myths, Best Time To Plant Trees