It’s March and the drab winter has worn out its welcome. If you’ve taken advantage of the occasional warmer days to inspect your garden, it is tempting to start pruning what looks like dead stalks on your hydrangeas.
A successful gardener must always have a specific goal in mind with each project or task in the garden. Before hacking the old hydrangea growing in the corner, first determine your goals for the hydrangea. Are you pruning to give the hydrangea a more desirable shape, or to get that wild beast under control? Or maybe you are pruning to achieve more lovely, large flowers. Perhaps you are pruning for all of these reasons. Let’s explore the ins and outs of successful pruning, or “pruning with a purpose.”
Before dusting off those pruners, get to know your shrub....
Before getting started, know what type of hydrangea you are growing. The type of hydrangea will determine how you begin to prune. The leaves, flowers, and growth habits are the key to identifying the type of hydrangea residing in your landscape. Common hydrangeas belong to four different species but there are five common types, each with slightly different pruning requirements.
Identify Your Hydrangea
Hydrangea Anatomy Matters
Your hydrangea’s stems matter. In order to achieve a full, thriving plant after pruning we need to know what to cut and where to cut. A good rule of thumb when pruning is to remove no more than ⅓ of the total plant. Cutting excessively can severely wound the plant, even to the point of death. Always remove thin, weak, and dead branches. Suckers should be removed as well.
Where to prune is based on old wood and new wood. Old wood is stem growth that is older than a year. New wood is stem growth from this growing season. Old wood is hard, brown, and rigid. New wood will be more succulent and green, and may be bendable and less stiff. How you handle this wood determines what type of hydrangea you own, and your pruning goals.
Nodes are the point at which buds form. Nodes give rise to leaves, stems, and flowers. These are the growing points on your shrub. When pruning, you want to cut at a 45 degree angle, just above a node. This creates a healthy place for the plant to recover from the cut.
Hydrangea Anatomy Matters
To Keep or Cut?
Panicle and Smooth Hydrangea
Cut these in winter or in early spring, because you will get flowers on this new growth in the summer. You can prune up to 50% of the total plant, but the more you cut, the larger the flowers will be. This can lead to flowers that flop to the ground. So be wary of cutting these to the ground. It is useful to use the thinning technique with these, because the new growth is what matters!
Oakleaf, Bigleaf, and Climbing Hydrangea
Cut these in the summer, after the flowering has stopped. Use the heading method when trying to get better flowering. These hydrangeas are most likely to keep their natural shape, and need less reshaping as an aggressive pruning.
Pruning to Decrease Size
Reducing the size of a hydrangea can reduce flower production for the year. The cost of flowers for the year results in a healthier and attractively shaped bush. The first step is to remove dead and decaying plant tissue that is on the ground. The next step is to cut all suckers from around the plant that may be popping up through the soil. The ‘thinning’ technique should be used. This means the location of the pruning is important: the cut should be made where the stem originates, rather than cutting the tips of the stem. This will keep the plant’s natural shape, and less new growth will arise from them as well. At points where the hydrangea is getting too large, cut all the way to the base of the stem. Remember! Don’t cut away more than a third of the plant. You should focus on trimming the top and inner parts of the plant. This allows light and airflow to reach the inner parts of the plant. Thinning the center and top develops healthy buds and prevents disease. Warning: Cutting wood (whether old or new) can affect the amount of flowers for this season.
Pruning to Enhance Shape
The key to enhancing a shrub’s shape is to stick with the plant’s natural growing habit. This makes a happy, healthy, thriving shrub. Maybe you tried pruning in the past, and the result was a mounded, irregular, lopsided hydrangea with no defining feature. The ideal hydrangea shape (except the climbing type) is a round shape with semi arching branches. Start by thinning the shrub. Place cuts at the base of the stems. Prune just above a node on the shrub. Look at which direction the node is facing. This is the direction the branch will grow. Do you want a branch to grow in this direction? It’s something to think about. Try and prune large, thick stems while keeping smaller, thinner stems. If you have oakleaf or bigleaf hydrangeas, this may result in loss of flowers for the season. The remaining stems act like a skeleton to reshape the shrub. Prune for your desired shape while trying to maintain the natural habit. If the shrub is too tall, focus on removing the larger, central stems. And always remember the 1/3 rule. Prune the top and thin the center. This will keep a shrub healthy and happy.
Hydrangeas are treasured flowering shrubs, admired for their pretty foliage, delicate flowers, and variety of bloom color. They are not particularly difficult to grow. But knowing when and how to prune them has stumped even the seasoned gardener. If you don’t already know the type in your yard, start there; then place a plant tag near your hydrangea. Or note the type in your garden journal. Hoping your hydrangeas provide you with armfuls of glorious bouquets!
Our guest writer for this blog is Paige Alcorn. Look for her contribution next month on deer resistant annuals.
My name is Paige Alcorn and this spring I will graduate from Penn State with a turf grass science major accompanied by a horticulture minor. I love learning about different ideas and tricks on maintaining beautiful turf grass and plant material. At Penn State you can find me growing flowers, vegetables, and herbs in the greenhouses with Gwen’s son, Dan. I am an avid horseback rider, and have won the Quarter Horse Congress show in 2009 and 2018. I have also rescued an off the track thoroughbred, and produced him to the Preliminary level of United States Eventing.
I have experience as a crew member at a minor league baseball stadium, interning at high end golf courses, as well as working with my professor on a preliminary herbicide study. I volunteered on the turf management teams at the PGA Women’s Championship Tournament and the 3M Open PGA Tournament during the summer of 2019. Through my 2019 internship with Land O’ Lakes Inc.
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