What’s the Best Fertilizer for an Ash Tree?

The best fertilizer for an ash is a slow-release tree formula applied once or twice a year, placed below the grass roots near the drip line. Just as important: ash trees are under serious threat from emerald ash borer (EAB), and fertilizer supports vigor but does not protect against it.

Feeding an ash tree

Feed an ash once or twice a year in the growing season. Choose our slow-release tree fertilizer with balanced macro- and micronutrients, apply below the grass roots near the drip line, and water in. Avoid quick-release lawn feed, which forces weak growth.

Don’t overlook emerald ash borer

EAB is a devastating wood-boring beetle, and even healthy ash trees are attacked. Protection requires a systemic insecticide — a once-a-year imidacloprid soil drench is used against EAB. Feeding alone won’t protect the tree.

Frequently Asked Questions

When should I fertilize an ash tree?

Once or twice a year during the growing season.

Does fertilizer protect against emerald ash borer?

No. EAB requires a systemic insecticide treatment; fertilizer only supports general health.

Should I fertilize a tree already infested with EAB?

Address the borer first. Ask an arborist whether the tree is a good candidate for treatment before investing in feeding.