Have you noticed here and there the beautiful white (and pink) blossoms on small (4′-9′ tall) trees over the last 5-6 weeks? You have probably been admiring the lovely mid to late summer blossoms of the hardy hydrangea trees.
The whole paniculata family of hydrangeas are exceptionally cold hardy, and are useful in the landscapes in both shrub form and also when carefully trained into small trees.
My wife and I are frequent visitors to the Boundary Waters Canoe Area Wilderness, which takes up to Ely, MN on a regular basis. I gained an awful lot of respect for hardy hydrangea trees when I noticed several large specimens growing in the front yards of homes in Ely, where -40 degrees temperatures occur almost every winter, and sometimes as low as -55 degrees. The trees were in full bloom in late July to late August and had to be 30-50 years old or more, judging from the trunks that were up to 6″ in diameter!
Besides hardiness, hydrangea trees are easy to prune and keep under 8′ tall, since even after a very aggressive pruning in late fall or early spring, they will bloom splendidly by mid to late summer on the new shoots that grow out quickly in early summer to form a handsome head. They also have few pest problems, and can prosper in light conditions from full sun to fairly heavy shade.
Make sure you water hydrangea trees very consistently the first year after planting. They use large amounts of water and during the first couple of seasons most of the water will need to come from your hand watering. Once they are established, hydrangea trees can get along mostly on rainwater, except for a few waterings during long dry spells.
I recommend fall pruning for the hydrangea tree. In mid to late October, it’s a good idea to cut off all the spent blossoms so that the heavy wet snow or ice storms won’t weigh down the branches to the point where they break.
Hydrangea trees are great for smaller spaces. many varieties are becoming available such as PeeGee Hydrangea, Limelight Hydrangea™, Pinky Winky Hydrangea™, Pink Diamond, Quickfire®, Kyushu and for the last blooming, Tardiva. Quickfire has become a variety of mine because its branches keep a nice upward thrust and the lacy open white blossoms appear to be floating on air. Tardiva is great for late season impact, since it’s blossoms attain their most vibrant appearance right when the blossoms of other varieties are finishing.
I have also shared this post with the Northfield News.