Tracking the Spring Leaf-Out

Close-up of tree bud

Welcome Spring

There are few more welcome signs of spring than when bright green leaves begin to unfurl from the empty branches we’ve been looking at all winter. So, when will trees show off their fresh, new looks?

The first glimpse of green we often get is from tulips and crocuses poking out of the ground, but it won’t be long before forest floors come alive with spring ephemerals. Shrubs are usually next to leaf-out so they can take advantage of the available sunlight before the tree canopy closes in. Trees take a bit longer since they need to move water and nutrients up and down their trunks to produce leaves. Trees that are structured with numerous small vessels can start this process as soon as it’s warm enough, so they’re often the first ones to leaf-out. Some of these earlier species include maples, cherries, poplars and birches. Meanwhile, trees like oak, hickory and walnut have larger straw-like vessels that are often damaged during cold winters and re-built-in spring, so their leaves take a little longer to appear.

Depending on the weather, we likely won’t see leaves on trees until sometime in May. Thankfully, we’ll see other signs of spring before then. If there’s a red or Freeman’s maple in your neighbourhood, head outside and look up at its branches. You’ll likely see clusters of pretty, red flowers that might just distract you from the thought of another spring snowstorm. Aspens and willows will show off their soft catkins long before we see their leaves, and some larger shrubs like serviceberries will also delight us with beautiful blooms before they’re washed in their summer green.

Monitoring projects around the world are tracking the connection between leaf-out dates and global warming. If you’re interested in contributing to this research, check out the community science project Budburst and consider submitting data from your own yard.

Photo credit: Melanie Kramer

Scroll to Top