Knowledgebase
Blue Spruce #870854
Asked May 30, 2024, 7:30 PM EDT
Hennepin County Minnesota
Expert Response
Thanks for your question.
I can confirm that you are dealing with Colorado Blue Spruce (Picea pungens).
If this tree was watered extensively last fall (2023) up until the ground froze, and if it has been watered this spring (2024), it is unlikely that a lack of water is causing the lack of interior needles.
Two possibilities come to mind:
1). Like many conifers, Colorado blue spruce naturally sheds its older needles, usually those on the interior of the tree. This is a normal process where older needles (typically 3-7 years old) turn yellow and drop off. Since your tree is approximately 30 years old, I would have expected you to have observed this needle browning and drop before now (spring 2024).
2). A more likely possibility is that the tree is infected by one of three diseases: Cytospora Canker, Rhizosphaera Needle Cast, or Stigmina Needle Cast. In fact, this is why Colorado Blue Spruce is no longer recommended as a suitable tree for planting in Minnesota. Please see the following:
https://trees.umn.edu/blue-spruce-picea-pungens
At this site, scroll to the section on Colorado Blue Spruce: https://extension.umn.edu/trees-and-shrubs/choosing-evergreens-your-landscape
https://extension.umn.edu/plant-diseases/cytospora-canker
https://trees.umn.edu/sites/trees.umn.edu/files/2021-10/stigmina_faq_sheet.pdf
https://apps.extension.umn.edu/garden/diagnose/plant/evergreen/spruce/needlesdiscolored.html
https://extension.umn.edu/plant-diseases/rhizosphaera-needle-cast
Here’s the bottom line. I don’t believe lack of water is causing this condition. More likely, the spruce might be showing early stages of a needle cast disease. This is why the tree still has a healthy appearance. As a first step, I would suggest that you contact a licensed, professional arborist to make an onsite inspection. Often there is no charge for this. See:
https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional
Then secondly, as a check on what this arborist might tell you, submit tree samples to one of the following plant disease diagnosis laboratories. Contact them first before sending in any samples as to what should be submitted:
Good luck. Please feel free to get back to us with any additional questions. Thanks for consulting us.