Prolific production of pollen cones

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Earlier this spring we reported that this year has been a big year for cone production in Fraser fir. The cones are a bane for Christmas tree growers since the cones need to be removed to maintain the marketability of their trees. We have also received calls regarding heavy pollen cone production in conifers in the landscape this spring. The problem has been most acute in spruces (especially Colorado blue spruce) and in concolor fir. As the pollen cones dry they turn brown. In some trees, pollen cone production is so prolific that the tree takes on a brownish cast. Some homeowners have mistaken the dried pollen cones for signs of insects of disease.

The heavy pollen cone production, although unsightly, does not pose any long-term problem for the trees. Spruces, firs and Douglas-fir have a two-year cone production cycle. As an evolutional adaptation to reduced self-pollination, female cones are usually produced in the upper one-third of the tree crown, whereas pollen cones are mostly found in the middle one-third. Reproductive buds are formed in the summer of the first year and then flush in the second year. So the outbreak of pollen cones we’re seeing this year is related to environmental signals the trees received last summer.

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