Soil pH under conifers

As the misconception goes, plants will not grow under spruce trees because the fallen needles make the soil too acidic. Is this actually true?

While it is true that nothing seems to grow under spruce trees, needles are not the problem. Plants fail to grow because the soil is depleted (lacking organic matter) and because the plants lack sunlight and moisture. Both shallow and exposed tree roots may also interfere. While spruce needles themselves are somewhat acidic, the soil beneath evergreens is not much different than the rest of the soil in your yard. This is because free lime is already in our soils and because the buffering capacity of Prairie soil actively resists changes in pH.

Avoid planting under conifer trees and leave them in their natural shape including low branches. This is best for the tree long term. If you really must plant under your conifer, a few ways to improve your chances include:

• Mulch under the trees to improve the existing soil (take care not to cover exposed roots or the base of the tree trunk).
• Consider removing some lower branches to let in more sunlight.
• Select plants which like dry shade and plant in groupings in prime growing locations, leaving the less ideal areas unplanted but well mulched.
• Regularly water plants until they’re established (continue watering periodically to maintain adequate soil moisture).
• Set out containers of shade-loving plants. Water by hand.