The Q&A Archives: Non Blumming Blue Nikko, Winter Care

Question: I have a small / dwarf Blue Nikko Hydrangea.
I bloomed very well after it was planted, the first year.
I did NOT prune at all, and covered it for winter using a styrofaom "rose cone". It is on the north/north east side of our home. Has been well watered and fertilized. Possibly too much or with wrong amounts. This year the plant grew twice over, and survived a dry spell. But did not bloom at all. (Am thinking amount of sun and fertilizer did it.) But am wondering if it should be covered again for winter. As we have already had one "hard" freeze. Have not receieved any snow, yet. But area where planted sees a lot of snow and wind.

Answer: This hydrangea would not really be expected to be hardy in your area, it is considered hardy to Zone 6 only. So you have done well to keep it alive! It blooms on buds formed on wood from the previous year. If it is exposed to too much cold, the buds and/or wood will die back. Freak spring frosts can also damage the buds. As the plant grows larger it is more difficult to protect it over the winter, and in an exposed location it is possible you will not be able to protect it enough. On the other hand, more established plants do seem to have a little more resistance to cold. To try, I would suggest starting with a wind break and a heavy layer of mulch over the roots. (snow is also a good insulator.) Make sure the plant is well watered up until the ground freezes. Once the weather turns cold and rodents have found homes elsewhere and the plant has gone dormant, erect a support around the exterior of the shrub and wrap that with burlap. Fill the interior with an insulating material such as dry oak leaves or fluffy dry straw. Place a waterproof roof over top to keep out rain and snow. Some gardeners will also encase the wrapped shrub completely down to the ground with plastic sheeting (making a mini greenhouse or polyhouse), however this creates a risk of overheating on sunny days and condensation inside. In spring, remove the insulating material gradually as the weather turns, and be sure to keep some handy to cover the plant if a late freeze threatens. Any needed fertilizing should be done in spring, fertilizing late in the season or in fall will possibly cause very tender growth that will not have time to harden before winter. Finally, do not prune in the fall or spring except to remove truly dead material. Any optional pruning should be done immediately after it blooms. Best of luck with your hydrangea!

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