A Comprehensive Guide to Caring for Hydrangeas

Secrets of proper care and feeding for your hydrangea

Hydrangeas are full sun to partial shade plants that appreciate moist, well-drained soil. Lots of organic matter will help here, although the nicest hydrangeas I’ve seen were all on Nantucket and Martha’s Vineyard in virtually pure sand; I suspect it’s simply the moist part that’s important; water copiously. We’ll talk about pruning hydrangeas as well as other factors that affect color, growth and health.

As to feeding, don’t feed new plants until established (1 to 2 months) and then use a balanced fertilizer. Feed sparingly, as too much nitrogen stops flowering.

Hydrangea Color

The other big question with feeding hydrangeas is flower color. Acid soils give us blues and baser soils cause pink flowers. The key is aluminum ions in the soil, so aluminum sulfate is a good quick fix, but prolonged use year after year may cause a fatal build up in the soil. Iron sulfate is a safer fix, or try alternating. If pink is what you want, top dress with dolomite or drench with a quick lime solution.

Why Hydrangeas Fail to Flower

Hydrangeas fail to flower for several reasons. Most common would be frost damage, followed very closely by late pruning. Too much shade or nitrogen are other likely culprits, but lets look at siting our plant and pruning as our best controls. If your hydrangea is not flowering look at your growing practices and where you have it planted and make appropriate changes.

Partial shade means more than four (more like six) hours of sunlight. Finding a more sheltered spot may help. But I suspect that the reason 9 times out of ten is pruning practices. Let’s review….

How to Prune Hydrangeas

Incorrect pruning is the biggest downfall of hydrangeas. Too much pruning and the macrophyllas won’t bloom, too little and the paniculatas become in Michael Dirr’s words “Monstrosity in the landscape.”

The vine and big leaf types should be pruned immediately after flowering or not at all! Cut back to a good pair of buds, the last pair if you want to dwarf the plant back some. The panicle hydrangeas should be pruned in winter or very early spring and pruned HARD. Selecting 5 to 10 canes will produce the huge panicles most people are looking for. Besides, at 15 feet, Pee Gee needs reigning in. Cut it back to that last pair or two of buds. You’ll be glad you did in 10 years.

Pests and Disease

While the list of diseases (wilt, blight, leafspot, rust) and pests (rose chafer, scale, mites and nematodes) seems daunting, I would tell you I have never actually seen any of these, and don’t expect to. I have seen powdery mildew, but this is easily controlled with benomyl, oil or lime sulfur (the latter two will discolor blossoms). Generally the biggest problems with this plant are siting and culture, so find a sheltered, partly shaded spot, water regularly, and soon your summer and fall will be filled with hydrangeas.

Summer is good

Hydrangeas can be the backbone of most summer borders. Their cultural requirements lend themselves to combining with roses (in a full sun situation; both need plenty of water), weigelia, spirea, and any number of other summer flowering shrubs. Let’s not forget the perennial border; there are any number of possible combinations there. All in all, hydrangeas are a versatile plant that deserves a place in your garden.