When/how To Prune Hydrangeas

Question

Don’ know type/name of hydrangea Cut plant back by one third, no blooms and took a long time to recoup

Answer 1

Depends on the type of hydrangea (see the link below). Normally, macrophyllas (aka, Big Leaf Hydrangea, French Hydrangea, Hortensia Hydrangeas), serratas (aka, Mountain Hydrangeas), quercifolias (aka, Oakleaf Hydrangeas) and anomalas (aka, Climbing Hydrangeas) produce invisible flower buds for spring 2022 at the ends of the stems by the end of summer 2021 or the start of fall 2021. See the link below to determine which type you have. Note: if the above named types of hydrangeas typically lose all stems during winter in Marengo, you could prune the stems now all the way down. However, pruning normally triggers new growth that may get zapped by early frosts (the average date of first frost in Marengo is the first week in October) so, I would prune after the plant has gone dormant or at the end of winter.

If your hydrangea is an arboescens (Smooth Hydrangea or Annabelle-like Hydrangea) or a paniculata (aka, Pee Gee Hydrangea), you could prune those now since they will not produce flower buds until 2022. Hydrangea arborescens develop flower buds from mid spring to early summer (it depends on one's geographical location; earlier in the south and after in the north). Hydrangea paniculatas similarly produce flower buds a few weeks later than Hydrangea arborescens. Both can be pruned now or later but avoid pruning from mid spring 2022 to summer 2022.

You can deadhead (not the same thing as pruning) spent flowers at any time by cutting the peduncle string that connects the bloom to the stem.