As the summer months approach, trees will once again begin to sport their bright and colorful leaves. To make sure your trees thrive in 2024, it’s important to examine your tree care routine starting from the ground up — literally.
“Tree health and longevity begins with matching the plant with the soil. Soil characteristics determine tree selection for each site,” Beth Brantley, plant pathologist with Bartlett Tree Experts, says.
Brantley and experts from Arborjet and Davey Tree share what to know to make your soil and trees work in perfect harmony.
The right stuff
Most trees will grow well in loamy, well-drained neutral pH soils, according to Brantley. However, some species require special soil profiles, making it important to have a good understanding of what kind of tree you’re planting.
Some of those special requirements could include soil that is especially acidic, alkaline-rich or quick-draining. These types of soil will oftentimes need additional treatments to maintain healthy trees.
One example Brantley offers is a pin oak (quercus palustris), which requires moist, acidic soil because of its inability to obtain necessary nutrients in low-pH soils. For most tree species, Kevin Brewer, northeast territory technical manager for Arborjet, recommends a soil mix of 40 percent sand, 40 percent loam and 20 percent silt as it holds good moisture, but not too much.
“If the water drains too fast, you may need to irrigate or rely on rain more often than if you have clay. Water tends to stick around a lot longer and you can have saturated soils longer,” he says.
For contractors working in urban environments, Brewer says soils can often lack organic matter. To combat this, he recommends contractors use mulch and humic acids to enhance the soil’s ability to retain moisture and nutrients.
Add-ons
To add organic matter, Brantley recommends biochar, a black carbon produced from biomass sources like manure and plant residue. She says biochar helps to improve soil porosity and increase nutrient retention.
Contractors have several options for biochar applications, ranging from large chips to injections, according to Jason Parker, district manager for Davey Tree’s north Philadelphia, Pa., office.
“(Biochar) can go down in a large chip when you’re amending the soil,” Parker says. “It also can be spread like a pelletized material, which is great for turf. It can be injected into the subsurface with a liquid carrier like water. There are a ton of products out there that provide all kinds of different options. (The kind you chose) is going to depend on what kind of program you have for your trees.”
Before deciding on a product like biochar, contractors should complete a soil test. Brantley says this is the best way to ensure a tree not only survives but thrives.
Solving the problem
If a tree’s health starts to decline, Brewer says contractors should keep a close eye on its incremental growth.
For example, he explains that a young oak tree may grow around six inches each year. But if that same tree only grows around one inch each year, it’s a sign that something might be wrong in the soil.
“If you see that dramatically slowed growth, something is definitely wrong,” Brewer says. “First, you should look at the leaves. If they start to look yellow, you might be lacking in nutrient availability. If you have some wilting, you may have water issues. If there is some dieback on the leaves, you might have high salt in certain areas.”