Fertilizing 100+ Evergreens: Why Soil Test & Mycorrhizae Beat Bags of 11-34-0

You're spreading 11-34-0 and 11-62-0 (no potassium) around 100+ evergreens on a large Canadian acreage. They "seem alright," but you're guessing — and excess phosphorus can block mycorrhizal fungi, the trees' true partners.

Potassium: Don't Add Blindly

Potassium deficiency shows as premature needle drop. But needle lifespan varies: juniper/Douglas fir (10+ years), arborvitae/white pine (2 years), yew (3 years). If needles drop on schedule, you don't need potassium. Excess K induces magnesium/calcium deficiency — it sticks in soil unlike nitrogen.

The 21st-Century Approach: Mycorrhizae

• Ectomycorrhizal fungi partner with conifers, dramatically increasing P and water uptake.
• USDA Forest Service: "Most plants require mycorrhizae for normal growth."
• High soil P (>100 ppm) inhibits mycorrhizae — your 11-34-0 may be hurting them.
• Trees prefer ammonium (NH4+) nitrogen, not nitrate (NO3-) like grass.

Action Plan

1. Soil test — know what you have before adding anything.
2. Inoculate with ectomycorrhizal fungi (powder, sprinkle before rain).
3. Mulch with compost + wood chips — feeds fungi, builds soil.
4. Skip high-P fertilizers unless test confirms deficiency.

Read: "Mycorrhizae: Benefits and Practical Application" (USDA/Georgia Forestry). Your trees will thrive with biology, not bags.