How aggressively can I cut back large hydrangeas?

Question: Hello,
I have 3 Endless Summer hydrangeas in front of my house that have gotten very large.  They do well in the spring but by July are getting pretty wilted and have lots of brown spots on the foliage-I think it just gets too hot and sunny in that area by then.  I have read that they should only be pruned to shape the plants, but I would really like them to be smaller.  How aggressively can I cut them back?  If I cut them back a lot-say, by half-is it possible that I would get no blooms this year but they might recover by next spring?  My other option would be to move them to another area with more shade but given their size, that won't be easy.  Thanks for any advice!

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied February 15, 2023, 1:50 PM EST
response: The varieties in the hydrangea series 'Endless Summer' were bred to be reblooming, so this helps the plants produce at least some flowers each year when pruning or winter weather deprives them of the original set of flower buds. All hydrangeas in their group (Bigleaf Hydrangea, or Hydrangea macrophylla) bloom on old wood, which means the flower buds form on stem wood that grew the prior year. Buds are present and fully developed on the plants during winter that will produce the first flush of flowers later this spring and early summer. Some varieties of Bigleaf Hydrangea, 'Endless Summer' included, are capable of also flowering on new wood, which refers to the stem growth that they will be producing this summer. Since reblooming hydrangeas like these do both, they bloom over a longer period of time overall and also have this added "insurance" against losing too many old wood flower buds if the shrubs are pruned or if the winter is harsh (or we have a hard spring freeze after they've broken dormancy).  So, if you prune them now (or any time before the first flowers emerge), you will be removing the first stet of blooms for this year, but won't be taking off all blooms. Since flower removal doesn't harm the plant's general health, that's fine to do as long as you don't mind reducing the amount of bloom they will produce this year. In that situation, pruning can be done around March. Otherwise, they should be pruned around midsummer (July-ish) when those old-wood blooms are spent but new-wood buds can continue to grow anytime. We have heard from nursery growers that high summer heat (especially when our nights stay warm) is suspected of causing reblooming to stagnate or peter-out a bit, but in general, any impacts on summer bloom abundance won't be directly caused by winter pruning. Pruning stimulates growth, though, so eventually the trimmed shrubs will still reach their typical mature size (3 to 5 feet high for this variety) if not re-pruned each year or so.  Bigleaf Hydrangeas can be grown in full sun when the conditions are just right (wholesale nursery growers do this routinely, but they also irrigate a lot), but usually in gardens they fare best when sited in a spot with some degree of midday or afternoon shade. Dappled light instead of deep shade is best so they have enough light to fuel decent blooming. (They will survive in heavy shade, they just won't bloom well.)  Either solution you propose can work -- keeping them where they are now but pruning once or twice a year to manage size, or wrangling a one-time move of the shrubs to a partly-shaded spot -- depending on which creates the least maintenance work for you or lessens the plants' overall stress. If the plants remain in full sun, then monitoring them for irrigation needs can help avoid some of the wilting, though some of it will be unavoidable in really hot weather, even when the roots have enough moisture. When watering, try to only wet the soil instead of the leaves in order to reduce the risk of leaf spot infections (more of a cosmetic issue than a serious health threat for the plant); if you need to use sprinkler which wets their leaves, run it early enough in the day that the foliage has time to dry by nightfall.  Miri

responder: The Question Asker Replied February 18, 2023, 7:32 AM EST
response: Thank you so much for your detailed response!

responder: The Question Asker Replied February 18, 2023, 7:52 AM EST
response: Thank you so much for your detailed response!

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied February 20, 2023, 10:15 AM EST
response: You're welcome!