What Type Of Hydrangeas Do I Have And When To Prune Them If Needed?

Question

We moved into a new house in July and it seems like these hydrangeas never bloomed this year. When trying to identify them, everywhere I look online talks about the blooms identifying the type I would have. Looking to see what type of hydrangeas these are so I can know if/how to prune them to hopefully get some blooms next year! I haven’t done anything this summer with them yet except trim some low lying stems coming onto the concrete pad.

Answer 1

Hydrangeas can be best identified by observing the types of blooms that they develop, when they develop blooms, the shrub/vine's structure and their foliage. With limited information on your plants, here are some generalities to consider…

Hydrangeas that tend to have blooming issues are those that bloom only on old wood or those that bloom on both, old and new wood. That is usually limited to cultivars of Big Leaf Hydrangea (hydrangea macrophylla) and Mountain Hydrangea (hydrangea serrata).

Last December 22nd, there was an Arctic Blast that reduced or eliminated the spring blooms from many of those hydrangeas as far south as Texas and Georgia. Spring blooms originate from dormant, spring 2023 flower buds that those shrubs would have developed somewhere between July-September 2022 inside the ends of the stems. To prevent spring blooms, either (a) extremely cold weather, (b) early or late frosts or (c) wildly fluctuating temperatures that keep the weather warm, make the shrubs break dormancy and then crash well below freezing overnight could have killed old wood stems or the flower buds inside live stems.

Other possibilities: fertilizing late (the last application of a slow-release fertilizer should be done 3 months prior to your average date of first frost or around the 1st-2nd weeks of November); fertilizing with high nitrogen products like some formulations of Miracle-Gro or by getting lawn fertilizer close to the hydrangeas' very shallow roots; improper pruning of leafless stems (avoid pruning leafless stems until the end of May as that is around the latest that they sometimes can leaf out); pests that frequently visit and which can eat the flower buds include deer, rabbits and squirrels; very dense shade (may require transplanting to get more morning sun exposure but, in OK, strictly provide shade in the summer by 11am or earlier in OK… no 12pm summer sun, no afternoon summer sun and no evening summer sun in OK (this will avoid getting sunscorch in the leaves during the summer months).

Big Leaf and Mountain Hydrangeas have typically developed flower buds for spring 2024 inside the stem endings by now so they are always best planted where they can attain their estimated plant dimensions and never pruned (except to remove crossing branches or dead wood by the end of May in OK and the rest of the south).

In the future, you can consider using winter protection or enhanced winter protection to ensure reliable spring blooms. This is usually accomplished by encasing the shrub in chicken wire that is filled with either composted hay, organic mulch, extremely densely packed leaves/etc. or by encasing them using burlap. There are some examples of these methods in youtube; search for "hydrangea winter protection" to see a few videos.

Winter protection should be maintained from around your average date of first frost (1st-2nd weeks of November) through your average date of last frost (3rd-4th weeks of April). Fertilize starting around your average date of last frost.