Spruce with Rusty-Looking Needles


I live 25 miles north of Toronto and have clay soil. Some of my spruce trees’ needles, especially those facing south, look sunburnt, and then drop. The trees are 5 years old and look healthy, Is there anything I can do to correct this?


From your brief description, the problem sounds most like winter damage – e.g., sun scald. But it could be something else.  So here are a few resources that might help – they include photos as well as descriptions of  winter damage versus damage done by diseases/pests, as well as how to deal with winter damage:

  • University of Minnesota Extension. Spruce – needles – discolored needles.  This site has photos of different diseases/conditions that can cause needle discolouration. For example, infection with Rhizosphaera, winter injury, scale, mite, blight, rust, needleminer.
  • Ask a Master Gardener, Spruce problem  — This post mentions that issues like environmental stress, including sun scorch and wind, can provoke a tree to shed needles.
  •  The Province of Ontario’s Winter browning.  

If indeed your trees did suffer winter damage, to prevent this from happening next year, keep the tree as healthy as possible.  For example, prune out the damaged foliage now (end of May); buds may grow in and fill the “holes” you create. Fertilize in early spring or early summer with a high nitrogen fertilizer and water the trees well throughout the growing season and into the autumn.  Another article from the University of Minnesota Extension, Protecting trees and shrubs against winter damage , provides further suggestions.

All the best with those trees – please update us on how they do over the summer and into next spring!