A Better Way to Prune Smooth Hydrangeas

All of the hydrangea in thenative hydrangea works trial done at Mt. Cuba Centerbloom on new wood , which mean that the flower bud develop when the bush set off actively growing in bound and former summer . These plants can be pruned any clock time from downfall to early leap , and even if root are killed to the ground by extreme cold , the works will still blossom reliably in midsummer . Read about the respectable aboriginal hydrangea species here .

Perhaps due to this adaptability , annual spring cutbacks are a common landscape painting practice forsmooth hydrangeasand related cultivars . As part of our trial , the Mt. Cuba team sought to determine if there are any recollective - full term effect of heavy spring cutbacks . For three consecutive days , one good example of each hydrangea was veer back to about 6 to 8 inches above the ground .

The immediate result we comment , compared to unpruned control industrial plant , was that the plant life modernize more - compact habits . There was also a slight delay in bloom , though not as much as we have a bun in the oven . Generally , blooming was delayed by just a hebdomad or two . The plants that were cut back produced fewer flowers , but these inflorescences were often 20 % to 100 % larger than those of the control group . For model , ‘ Haas ’ Halo ’ , which normally has flower heads that are about 8 in across , had prime that were 12 to 16 column inch in diameter after a cutback .

We also acknowledge an strange gain in Lord’s Day permissiveness for cut - back plants , peradventure because their well - launch radical systems were support a smaller phone number of shank than they normally would have been .

Balanced cutback . off 1/5 to 1/3 of the oldest stems each class in recent winter .

Full cutback . Cut all stem 6 to 8 inches above the ground in late wintertime .

However , the cutbacks did not sort out floppy drug abuse , and they had little impact on the overall size of the more heavyset cultivars . After three years of weighed down one-year cutbacks , we start to notice a picayune burnout , epitomize by low-toned flower output in the reduce - back industrial plant .

base on these observations , we concluded that a full annual cutback is not the best practice in most eccentric . We commend rather a more balanced approach , in which a fifth to a third of the one-time stems are pruned to the ground each year in belated winter . This will aid keep the plant flowering well , it may keep the use a piddling more compact , and it is for certain loose on the flora than an all - out cutback every exclusive yr .

Sam Hoadley is the manager of horticultural inquiry at Mt. Cuba Center in Hockessin , Delaware .

Illustrations : Jessica Daigle

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