With Hydrangeas, NO pruning is better than incorrect pruning. In fact, most varieties will grow and flower to some degree if they are never pruned at all, provided that they are properly cared for and planted in a protected location (if required). When and how you prune your Hydrangea depends on the type of Hydrangea, and if flowers are produced on old or new growth. “Old Wood” are stems that have been on the hydrangea since the summer before the current season. “New wood” are stems that developed on the plant during the current season.
Annabelle (arborescens) and Pee Gee (Paniculata) flower on new growth. This includes Limelight, Quickfire, Pinky Winky, and Little Lamb types. No pruning is really necessary except to remove spent flowers, broken or entangled branches and for general shaping. The best time to prune is in early spring before growth begins, or late fall and winter. Annabelle Hydrangeas may be treated like woody perennials and cut down to 3” each spring to encourage compact growth habit. They will still bloom beautifully in the spring/summer, however this drastic pruning may not allow stems to increase in size, and they may need staking to hold up the large heads.
Endless Summer series flowers on old growth and new growth. Prune dead stem growth after buds emerge in the spring. Don’t treat your Endless Summer Hydrangeas like an Annabelle Hydrangea by cutting them back in the fall or early spring. By cutting to the ground or within a few inches of the ground, most if not all of the buds on old wood are being removed. In addition, the old blooms of Endless Summer add to the winter interest of your garden. Endless Summer Hydrangeas certainly do bloom on new wood, but it may take longer for flower buds to develop on the new growth of a young plant.
Oakleaf types flower on old growth. Delay spring pruning until growth has fully emerged. At this time, remove any winter damaged tips or stems that have not produced leaves. Once established (3 +years), Oakleaf Hydrangeas suffer little dieback if they are planted in a winter protected area, unless the previous winter has been extremely cold with sustained temperatures below — 10 F. Heavy pruning should occur immediately after flowering, while removal of an occasional branch or two for shaping purposes can be done at any time during the growing season.
Big Leaf and Serrata types flower on old growth. This group of hydrangeas produces flower buds on stems around August, September or October for the following summer’s blooms. Delay spring pruning until growth has fully emerged. At this time, remove any winter damaged tips or stems that have not produced leaves. Flower buds form near the stem tips during the previous year and may be accidentally removed if pruned back too far, and you may have a beautiful plant with no flowers because of winter die-back or incorrect pruning. Additional selective pruning may be done in late summer to remove the spent blossoms if desired.
Educate yourself about the plants that you have, and how they react to pruning. Find out when your plants bloom, and plan pruning according to that schedule. Spring-flowering shrubs and trees will have already set buds for the next year. Pruning in the fall removes the flowers that you’ve worked so hard to preserve.
Avoid pruning:
Perennials may be left to stand and provide winter interest, or maybe cut back to the ground. It’s a matter of personal preference. Some perennials provide food for birds and other wildlife through the winter if left standing.
Grasses should be left standing until spring. We’ve found that grasses survive better if left until early spring. At that point cut grasses back to several inches tall before they begin to show new growth.
If you’re not sure please contact us at the nursery (Phone: 260-637-5816) or contact the Allen County Purdue Extension Office (Phone: 260-481-6826)
Sources: Maintenance PruningHow to Prune Conifers (April 2009), Maintenance Pruning