Most established trees in Virginia don't need fertilizer at all, but almost every tree benefits from loose, healthy soil.
In a forest, fallen leaves and wood break down and feed the soil every year. Yards remove that cycle and add foot traffic, mowers and compaction. Rebuilding the soil does more for most trees than any bag of fertilizer.
Start With a Soil Test
Don't guess. Virginia Cooperative Extension offers low-cost soil testing through Virginia Tech's Soil Testing Lab. Pick up a kit and instructions at your local Extension office. The results tell you your soil's pH and nutrient levels, and whether you need to add anything at all.
Know Your Soil
- Coastal Plain (Hampton Roads and the Eastern Shore) soils are often sandy and acidic, and they drain quickly. Some low areas have heavy, wet clay and a high water table.
- Piedmont soils (Richmond, Fredericksburg and west) are often red clay that compacts easily and drains slowly.
- Most Virginia native trees prefer slightly acidic soil, roughly pH 5.5 to 6.5.
Watch for Yellow Leaves With Green Veins
That pattern, called chlorosis, often means the soil pH is too high for the tree to take up iron or manganese. Willow oak, pin oak, sweetbay magnolia, river birch and bald cypress are prone to it. It's common near concrete foundations, driveways and areas that have been limed for lawn. A soil test will confirm it. Lowering pH is a slow process, so the fix starts with not adding more lime around acid-loving trees.
When Fertilizer Makes Sense
- Only when a soil test shows a real deficiency, or a tree shows weak growth with no other cause.
- Use a slow-release fertilizer spread evenly over the whole root zone, not piled at the trunk.
- Apply in early spring or in fall after leaves drop.
- Don't fertilize newly planted trees for at least the first year.
- Don't fertilize a tree stressed by drought, root damage or disease hoping to revive it. It pushes new growth the tree can't support.
Be Careful With Lawn Products
Tree roots spread far under the lawn and take up what you put on the grass. Some broadleaf weed killers, including combination "weed and feed" products, can injure trees and shrubs through their roots. Read labels closely and avoid using them over tree root zones. Heavy lawn fertilizing can also push soft growth that attracts aphids and other pests.
Fix Compacted Soil
Signs of compaction include water pooling or running off, bare hard ground, and roots showing at the surface. To improve it:
- Replace lawn under trees with a wide mulch bed.
- Keep cars, equipment and foot traffic off the root zone.
- For badly compacted soil around valuable trees, arborists can loosen soil with compressed air tools and work in compost without cutting roots.
Let the Leaves Work for You
Instead of bagging every leaf, run over them with a mulching mower and let them fall into beds around trees. You'll recycle nutrients and organic matter right where roots need them. The exception is leaves from trees with leaf diseases, like dogwood anthracnose. Rake those up and remove them.