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Hydrangeas

Jun 08, 2018

Hydrangeas are a popular garden favorite and for good reason too. Perfect for part shade, these mid-size shrubs brighten gardens in the summer with their large clusters of blooms. Hydrangeas come in many varieties and are relatively easy to care for.

Perhaps the most commonly known hydrangeas are Bigleaf hydrangeas (h. macrophylla). These hydrangeas have either large, mophead, round blooms or flat-topped, lacecap blooms that are usually pink, blue or white. In the pink and blue varieties, color will vary based on the acidity of the soil and soil can be amended to change the color of the flowers. Pink hydrangeas will turn blue when the soil is more acidic and likewise blue hydrangeas will turn pink when the soil is more alkaline. One of the most popular varieties of bigleaf hydrangeas is ‘Endless Summer’ which is known for reliably re-blooming throughout the summer.

Annabelle hydrangea (H. arborescens ‘Annabelle’) is a cultivar that is native to the US. It has 8-12 inch white mophead flower clusters with sturdy stems and blooms late spring, persisting until fall.

Panicle hydrangeas (H. paniculata) have cone-shaped flower heads and are one of the last hydrangeas to bloom, flowering from mid to late summer. Their flower heads are 6-18 inches long and white, with many varieties fading to pink or red as the blooms age. Panicle hydrangeas can tolerate more sun than other types of hydrangeas and are also more cold hardy. Some varieties of panicle hydrangeas can grow to be as large as 20′ and can be trained as trees, but dwarf cultivars exist as well.

Oakleaf hydrangea (H. quercifolia) is another US native. With flowers similar to the panicle hydrangea, oakleaf hydrangeas have large, oak-like leaves. When the flowers start to fade in the fall, the leaves continue to provide interest with their showy autumn color, and in winter their exfoliating bark is exposed.

Climbing hydrangeas (H. anomala petiolaris) are woody vines with fragrant, white, lacecap-like flowers blooming early to mid-summer. They can be slow to establish, but once mature have thick vines with exfoliating bark. Climbing hydrangeas do well with something substantial to grow on and climb nicely up walls and other vertical structures.

Caring for hydrangeas is fairly easy, but knowing when to prune them is important to keeping them looking their best. While hydrangeas don’t necessarily need to be pruned yearly, occasional pruning can help keep them an appropriate size and also help improve the shrubs vigor and increase bloom size. If pruned at the wrong time of year however, your hydrangea may not bloom the following season.

Bigleaf hydrangeas and oakleaf hydrangeas bloom on old wood and should be cut back late summer when the flowers start to fade. To improve vigor, cut back the oldest canes to the soil line. If you’re just looking to tidy up, remove any old blooms and scraggly canes.

Panicle hydrangeas and Annabelle hydrangeas bloom on new wood, and should be cut back in late winter before the new growth begins. These can be cut back to 18-24 inches tall to allow sturdier stems and reduce flopping, or can be cut back all the way, which will result in weaker steams, but encourage large abundant flowers.