Knowledgebase

European Mountain Ash? #770789

Asked September 05, 2021, 10:40 AM EDT

Hi there, I was hiking in the James Peak Wilderness area and came across this tree/shrub with polka-dotted leaves. Is this, in fact, a European mountain ash? And if so, what causes these dots? Thank you! Laura

Boulder County Colorado

Expert Response

Hello Laura and thanks for your questions!

That is very likely a European Mountain Ash! I've attached a link below that includes a little more information for making a positive identification. And I believe the spots you noticed are very possibly some type of rust. The second link below provides more information on fungal rust diseases we see here in Colorado.

Hope you enjoyed your time in the James Peak Wilderness!

Warm regards,

Colorado Master Gardeners

European Mountain Ash - Colorado Master Gardener (colostate.edu)

1400-22 - Foliar Rusts on Leaves of Plants - PlantTalk Colorado (colostate.edu)

An Ask Extension Expert Replied September 08, 2021, 11:39 AM EDT

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