It’s the number 1 question asked about Hydrangeas. When is the safest time to prune my Blue Hydrangeas without affecting the flowers for next year? Well the answer is now!
There are two types of Hydrangeas out there- those that bloom on “old wood” (stems that have been on the plant since last year) and “new wood” (stems that developed this year). Most Hydrangeas in our gardens are the varieties that bloom on “old wood”. What that means is very shortly after flowers have developed and are now fading away from this season, the flower buds are already forming for next years’ showing. It’s these plants that we often have trouble with since they require a specific time of year where we can safely cut them back without removing the buds for next year. By the end of August and through September, new buds are being formed on the stems of hydrangea branches and will lay dormant all winter long only to burst open early summer of next year.
Hydrangeas really don’t need to be cut back unless they’ve outgrown their planted location, are full of dead stems or are old plants that need to be revitalized and cut back in size. In these cases, now is a good time to get out there and prune out both live and dead stems or cut the plant back if necessary. Never cut back more than ½ the plant size and give it plenty of water when you’ve finished. If you just want to deadhead the fading flowers then remove the flower heads only back to the next set of leaves.
Hydrangeas that bloom on “old wood” consist of Mophead, Lacecap and Big Leaf varieties (hydrangea macrophylla) and the Oakleafs (hydrangea quercifolia).
“New wood” bloomers are those that produce flowers on this seasons growth and are less of a concern since flowers will form no matter when you prune them. These consist of the Tree Form varieties (hydrangea paniculata) and the Smooth varieties (hydrangea arborescence). These are often pruned in the fall before the plants go dormant, or the spring before they begin to leaf out.
There are also the “Endless Summer” hydrangeas that have been bred to produce flowers on both old growth and new. They are both of the Mophead and Lacecap varieties. Pruning them at the wrong time of year may remove developed buds on the old growth stems, but you’ll still get flowers produced on the new growth. It’s still a good practice to cut them back right now if you need to and want the best showing of flowers next season.
So if cutting back your hydrangeas has been on your “to do” list this season, get out there this week. The window of opportunity is closing as those new flower buds are about to take place, bringing new life to probably our most recognized shrub in the garden world.