"Old Wood" Vs "New Wood" Hydrangeas: What's The Difference? (& Why It Matters)

Hydrangeas bring an iconic color pop to any garden or landscape, standing out with their unique flower clusters. When it comes to growing these vibrant beauties on your own, it can be complicated if you're using the wrong techniques. While hydrangeas share a similar look, their care requirements depend on whether they're an old or new wood species. When hydrangeas grow on old wood, the plant produces the buds for the next year right after their blooms fade for the season. Once these buds are formed, frost or dropping temperatures can shock them, preventing blooms the following year. New wood hydrangeas sprout their buds on new growth when it's time to bloom, and they can often better endure cold environments.

Some common old wood hydrangea species include bigleaf hydrangeas (Hydrangea macrophylla), mountain hydrangeas (Hydrangea serrata), oakleaf hydrangeas (Hydrangea quercifolia), and climbing hydrangeas (Hydrangea anomala ssp. petiolaris). When it comes to new wood hydrangeas, common varieties include panicle hydrangeas (Hydrangea paniculata) and smooth hydrangeas (Hydrangea arborescens). If you're looking for hydrangeas that will bloom multiple times throughout a season, the 'Endless Summer', 'Twist 'n Shoot', and 'Summer Crush' cultivars of the bigleaf hydrangea species grow on both old and new wood.

How can you spot the difference? Old wood has a thicker, more wooden appearance. In contrast, new wood is greener and more flexible. Look at your hydrangea's flowers to see which type of stems they're growing on. The distinction between old wood and new wood species may be the reason your hydrangeas aren't blooming in a colder climate. It also determines how and when you should care for your hydrangeas when it comes to maintenance, like pruning.

Choosing between hydrangeas can be a big decision, especially when you consider their different needs. One of the benefits of growing new wood hydrangeas is that they are easier to prune since there's less risk of accidentally pruning buds and preventing flowers. Overall, the only use for pruning hydrangeas is to shape or control the size. When pruning either type, the timing matters. New wood hydrangeas can be pruned from late winter to early spring before their new buds begin to form. Old wood hydrangeas must be pruned immediately after they finish blooming to avoid pruning any new buds for the upcoming year.

Old wood hydrangeas have their own benefits, like blooming faster when spring arrives since their buds have already formed the previous year. On the other hand, they'll need more winter protection if the buds are going to make it to spring. Mountain and bigleaf hydrangeas can survive winter in USDA Hardiness Zones 6 through 9 and 6 through 11, respectively. Oakleaf hydrangeas can endure zones 5 through 9, and climbing hydrangeas are the hardiest, surviving zones 4 through 8. If you live in a climate where winter temperatures consistently dip below freezing, you may even want to protect new wood hydrangeas, which can survive down to zone 3.

Start by adding a layer of mulch to the base of your hydrangeas. In colder climates, take things further by building a barrier for insulation. You can create a protective structure with frost protection fabric or burlap. Keeping hydrangeas hydrated can also help protect their cells from damage if temperatures get low enough.