A better way to prune smooth hydrangeas

All hydrangeas within the check bloom on new wooden, which implies that flower buds develop when the bush begins to actively develop in spring and early summer time. The crops will be pruned anytime from autumn to early spring, and even when the stems are killed by excessive chilly, the plant will nonetheless reliably flower in mid-summer. Examine one of the best native hydrangea species right here.

Maybe due to this adaptability, annual spring cuttings are a standard landscaping apply for clean hydrangeas and associated cultivars. As a part of our check, the staff at Mt. Cuba sought to find out whether or not there are any long-term results of heavy cuts within the spring. For 3 consecutive years, one instance of every hydrangea was minimize about 6 to eight inches above the bottom.

The speedy consequence we seen, in comparison with unpruned management crops, was that the crops developed extra compact habits. There was additionally a slight delay in flowering, though not as a lot as we anticipated. Usually, flowering was delayed by solely per week or two. The crops that have been minimize produced fewer flowers, however these inflorescences have been usually 20% to 100% bigger than these within the management group. For instance, ‘Haas’ Halo’, which usually has flower heads about 8 inches in diameter, had flowers 12 to 16 inches in diameter after one minimize.

We additionally seen an uncommon improve in solar tolerance for minimize crops, presumably as a result of their well-established root techniques supported fewer stems than they usually would.

Nonetheless, cuttings didn’t right limp habits and had little influence on the general measurement of the extra compact cultivars. After three years of huge annual cuts, we started to note a slight depletion, characterised by decrease manufacturing of flowers within the minimize crops.

Primarily based on these observations, we concluded {that a} full annual mowing will not be one of the best apply most often. As a substitute, we suggest a extra balanced method, wherein one-fifth to one-third of the oldest stems are pruned to the bottom annually in late winter. This may assist preserve the plant flowering properly, it would preserve the behavior a little bit extra compact, and it is actually simpler on the plant than a full minimize annually.

Sam Hoadley is the Horticulture Analysis Supervisor at Mt. Cuba Heart in Hockessin, Delaware.

Illustrations: Jessica Daigle