Oak trees are some of our favorite trees here at Friends of Grand Rapids Parks. They contribute to local ecosystems, have really incredible and unique biology, and are beautiful, too. And how cute are their tiny, new spring leaves?
Here are three quick facts about oak trees that will (hopefully) help you love them even more and continue to care for any oak trees you may have near your home.
Oak Trees’ Ring Pattern is Why They Get Leaves Later than Other Trees
Oaks leaf out later than many other trees in the spring. When maple trees are bright green with leaves, oaks are still mostly bare. Why? Think about the rings you can see in the stump of an old tree. Trees grow one new ring every year, and the way the ring grows affects how the tree grows. Oak trees have wood that’s called ring porous; the largest water-conducting pores (vessels) are in the early wood, or the part of the tree ring that forms in the spring. In order to put out leaves, oak trees need to grow that first part of the year’s ring. It takes a huge amount of energy to grow a ring, so they’re delayed in comparison to diffuse-porous trees like maples. Maple trees’ vessels are more uniform and evenly-distributed throughout the year’s ring. This puts ring porous trees like oaks at a disadvantage compared to maples that can take advantage of sunlight earlier in the season. Here’s a neat illustration of how tree vessels look.
Don’t Prune Your Oak Trees in Spring and Summer
It’s spring in West Michigan, so time to stop pruning your oak trees! The picnic beetle—the insect that carries the oak wilt fungus—is now active, and they’re attracted to the scent of fresh cuts in oak trees.
Once the fungus touches the vascular tissue (the inside of the tree that conducts water), it clogs up the pores and prevents water and nutrients from moving through the tree. The disease moves quickly and can kill a mature oak within weeks. There is no treatment, and even a dead tree can spread the spores through roots grafted with other oak trees, putting them at risk.
The insect becomes less active in July and August, so some arborists will resume pruning around then, but the risk doesn’t fully drop until October. Winter is a great time to prune oak trees!
If your oak was damaged during a storm, you can prune it to clean up the damage and then use wound sealer or latex-based paint to cover the wound. Preventing vascular diseases like oak wilt is the ONLY time our arborists recommend using wound sealer!
Migrating Birds Love Oak Trees
Oak trees provide a lot of benefit to migrating birds in the spring. They host over 500 species of caterpillars, which is a big source of protein for birds. Later in the fall, the fat-rich acorns will be an important food source for blue jays, grackles, and wild turkeys.
Types of Oak Trees We Plant at Friends
We plant red oak, white oak, swamp white oak, and burr oaks most commonly, but sometimes plant oaks from a little further south, like overcup oaks. We are a little more likely to plant trees from the “white oak” group because of their resistance to oak wilt disease.
What makes them good street trees? Oaks used to be very common in Grand Rapids 200+ years ago. We had oak barrens, oak savannahs, oak-hickory forests, and mixed hardwood forests all throughout the city. Our acidic, sandy soil is ideal for oaks, who thrive in these soil types. Although they’re generally slower growing than other tree species, once they reach maturity, they have beautiful spreading branches that are very strong, and provide a lot of shade. Many oaks are tolerant of droughts, which is an increasingly-common occurrence in Michigan. We love planting oak trees and are excited to get more in the ground this year.
If you’d like to support our tree planting work, you can make a gift that helps us plant more trees in parks and parkways. Or, join a tree-planting volunteer workday.
See you out there!
