I have a climbing hydrangea that doesn’t flower. I’ve had it for 4 years. Is there anything I can do to promote flowering? My soil is clay and it gets morning sun. . I have endless summer and annabelle hydrangeas. When should I cut back last years growth? I left them over the winter. Thank you.
Thank you for contacting the Toronto Master Gardeners with your questions regarding pruning hydrangeas and absence of blooms on your climbing hydrangea.
Although climbing hydrangeas (Hydrangea anomala subsp. petiolaris) can take a few years to get going you should start to see blooms by now. Hydrangeas tolerate a variety of light conditions but partial sun may result in more blooms than deep shade. Hydrangeas also like water but not soggy roots. Your clay soil will likely benefit from the addition of compost to increase nutrients and soil structure which will improve drainage. Add some compost this spring and then mulch the soil around the plant (not touching the stem) with 1-2 inches of compost. Avoid pruning your climbing hydrangea (other than dead wood) until it has bloomed. You can prune as needed to maintain shape but only do so in the late spring / summer immediately after blooms die back. A previous Toronto Master Gardener post is linked below for additional information regarding climbing hydrangeas.
https://www.torontomastergardeners.ca/askagardener/training-and-trimming-climbing-hydrangeas/
Determining the time to prune hydrangeas depends on when and how they bloom. Some bloom on “old wood” that was formed in the previous growing season and some bloom on “new growth” formed during the current growing season. Your Annabelle hydrangea (Hydrangea arborescens) blooms on new growth and can be pruned in the late winter or early spring before signs of new growth begin. The Endless Summer hydrangea (Hydrangea macrophylla ‘Bailmer’ Endless Summer) blooms on both old wood and new growth. Prune in May once you can clearly see the buds on the old wood. Prune out only the dead wood or branches and avoid cutting off the buds. The plant should bloom later in the spring and then again late in the summer. You may find the two links below helpful.
Caring for Endless Summer Hydrangeas
Best of luck with your hydrangeas!