Guest Rant by Lorraine Ballato
It all started in early January, as it does every year: the steady stream of online advice about how to deal with hydrangeas before they actually flower this season. Want to be sure you get the least from your hydrangeas this season? Go ahead and follow online advice that keeps popping up. After all, if it’s on the internet, so it must be true.
When to Prune Hydrangeas
Herewith some excerpts from an online posting called Green Packs: “One of the most important things you can do for your hydrangeas in the fall is pruning…Additionally, pruning will encourage new growth in spring.”
WRONG! Pruning in fall in the Northern hemisphere, regardless of shrub, will stimulate the plant to grow when it should be using its energy to go into dormancy. You could possibly get away with this fall pruning on new-wood bloomers like ‘Annabelle’ or ‘Limelight,’ when they have gone completely dormant (i.e., no leaves), but why distract the plant?
And you definitely don’t want to prune in the fall any hydrangea species that flower on old wood, e.g., ‘Nikko Blue’, climbing hydrangeas, oak leaf hydrangeas, and mountain hydrangeas. For those plants, you are in the “Hydrangea Danger Zone.” That’s the late-season time frame when these old-wood plants put their flower buds on. They need nights consistently below 60 degrees (F) and short day-length (after June 21 in the Northern hemisphere when daylight hours start getting shorter).
By the way, this same science applies to other plants like forsythia, azaleas, weigela, et cetera Any time you prune or fertilize a hydrangea in the Hydrangea Danger Zone you send it the wrong message. Walk away and leave it alone until you see those little heads of “broccoli” – the new flower buds. They tell you which stems will give you flowers, so you can cut away.
Here’s another piece of advice, this time about fertilizer: “A balanced fertilizer such as 10-10-10 is ideal for promoting healthy growth and abundant blooms throughout autumn and into winter”
WRONG! No plant uses nutrients in equal amounts. Yes, it’s easier for you the gardener, but not so good for the environment. The excess unusable nutrients run off and pollute surrounding soil, waterways, et cetera. Any kind of rose or shrub fertilizer is much better because their nutrient levels are uneven, as is appropriate for these plants.
Fertilizer has its place, but not in the fall. Hold off until the spring. That’s a great time to fertilize to get those new season flowers going. Stimulation in spring is exactly what you want.
HOW to Prune Hydrangeas
More about pruning, whenever you do it. There are advisories to cut your new-wood plants to the ground or just a few inches above, as stated in this recent Lincoln, Nebraska article: “Smooth hydrangea is easy –simply cut all the stems down to the crown in either fall or spring before new growth begins” Or this Chicago Tribune article: “Smooth hydrangea cultivars, such as the commonly grown Annabelle and Abetwo (Hydrangea arborescens), respond well to being aggressively cut back in the dormant season. I prefer to cut them back at ground level or to about 1 inch above.”
Okay if that’s your preference, as the writer stated, but not if you want to prevent your flowers from flopping. New stems are too weak for the fabulous flowers, especially after a summer rainstorm. Of course, you could lace up your ‘Annabelle’ hydrangeas like Victorian maidens to keep the flowers up.
If you can’t resist the urge to cut the stems down to the ground, a better idea is to go after only about one in three stems. The other two that you leave up will be flowerless, but they will support the new floriferous stems. Plus, their foliage will help feed the plant, as photosynthesis produces the carbohydrates that root systems need to thrive.
The key to pruning shrubs is knowing if your plants flower on old wood or new wood. Or you can believe this little tidbit (again in Lincoln, Nebraska) about oak leaf hydrangeas, “Oak leaf hydrangea is a slow grower in Nebraska and often suffers stem dieback in winter. It also blooms on new wood but will not flower if the terminal buds winterkill.” The correct information is that oakleaf hydrangeas produce flowers only on old wood that grew last year. It has no chance of producing flowers in the current season on new growth. Oops!
And on it goes, with more to be published as the season progresses and we gardeners get itchy fingers. Keep in mind that much of what we gardeners do is gated by our geography. So if you garden in the Pacific Northwest, Great Britain, or Maine, timing will be somewhat different.
Finding Accurate Info
So what’s a hydrangea lover to do? Seek info from reputable local garden centers and hydrangea growers like Bloomin’ Easy, Proven Winners, Southern Living, Star Roses and Plants, Tesselaer, et cetera. Yes, they have a vested interest in exposing you to the wonders of their plants, but they also have the relevant info for home gardeners. After all, they want you to be successful with your plants so you will buy more.
There are loads of growers at the ready to answer your questions. A simple internet query that specifies your source (it could be one of the above growers or your favorite agricultural extension site) will yield correct information and more, and you will be off and running.
From a purely self-promotion standpoint, you could also avail yourself of my free hydrangea blog. There, a simple search for whatever hydrangea topic interests you will yield multiple informative posts that are backed by the science and grower data. I’m all about accurate hydrangea information, happy hydrangeas,and happy gardeners!