Dwarf Mistletoe

You'll spot dwarf mistletoe as small yellowish-green plants growing in clusters directly on branches, typically 0.75 to 4 inches tall. The real giveaway is the witches' brooms: dense clumps of stunted shoots or, in western larch, scattered aerial stems that emerge from a single internal infection point. These unusual growths become obvious in late spring and summer as branches swell slightly where the parasite roots into the wood. In Western Washington, you're most likely to encounter this on western hemlock and true firs, though it rarely appears at lower elevations west of the Cascades.

Dwarf mistletoe is a parasitic plant, not a fungus, which makes it particularly stubborn to manage. It weakens branches and eventually kills them, opening the tree to secondary decay. The parasite spreads via explosive seed dispersal in fall, with moisture washing seeds onto needles and new shoots below. Once established, it can take 2 to 5 years before visible symptoms appear. Your best option is removal: prune out infected branches entirely by midsummer when the yellow-green plants are easiest to spot. Removing just the aerial shoots won't work since the parasite will regrow from its internal infection point.