It seems like pruning has been the topic of choice lately, but it’s an important gardening chore this time of year. Hydrangeas, one of the more popular plants in the landscape, also require routine pruning.
Hydrangeas have attractive foliage and typically produce large, striking flowers. They generally are easy to grow and tolerate a wide variety of soil. About the only care they need is pruning; however, there are different types of hydrangeas requiring different pruning techniques depending on the time of flowering.
Hydrangeas that bloom in the spring, usually before May and June, bloom on last year’s growth. Those that bloom later flower from buds formed on the new wood of that growing season. Varieties that bloom in spring should be pruned after they flower, while those that bloom on new wood can be pruned, if necessary, in late winter or early spring before new growth develops.
So, which is which? The types that bloom on old wood include the mophead, big leaf and lacecap, which are Hydrangea macrophylla varieties, and the oakleaf hydrangea, H. quercifolia. These all produce flower buds on last year’s wood.
Varieties blooming on new wood include the panicle hydrangea, often referred to as PeeGee types; H. paniculata; and the smooth hydrangea, often referred to as the Annabelle types, H. arborescens.
The one exception is the variety ‘Endless Summer’, which blooms on both old and new wood. In all cases, it’s helpful to remove old blossoms as they fade.
If you’re not sure of which type you have, the safest approach is “no pruning is better than the wrong type of pruning.” However, gardeners also can take a simplified approach, which is suitable for all types. The simplified approach includes removing only winter-killed wood or all dead stems in the spring before or as the buds are opening. Check for live wood by scratching the stems with your thumbnail or a knife - if it is green it is still alive. If it’s brown and hard, unfortunately, it is dead and should be removed.
Rejuvenation is another way to keep your plants healthy. Remove dead or very old stems by cutting them back to the ground because this will stimulate new growth and produce more blooms later on.
Today there are a wide variety of hydrangeas; make sure you choose a variety that will suit your landscape needs, as well as the site. Most like some water and most prefer a little protection from the hot Oklahoma afternoon sun. With good choices, and correct timing with pruning, your hydrangeas will be the envy of the neighborhood.
David Hillock is a consumer horticulturist with OSU cooperative extension.