After 40 years in the landscape industry, I can say there isn’t a plant that creates more confusion than Hydrangeas. We must get 3-4 Hydrangea questions a year. Pruning Hydrangeas and a lack of flowers is often the cause of many of those questions. It’s hard to answer any Hydrangea related questions before knowing what variety of Hydrangea you’re dealing with. There are basically 5 major shrub Hydrangea. There are more but I won’t address them here because they aren’t seen commercially or they are a vine. You’ll need to figure out what type of hydrangea you have before knowing the timing of your pruning. The four main Hydrangeas you often see in Connecticut gardens are Oakleaf, Mophead, Lacecap and Panicle. Let’s break down each of these varieties and discuss when you’d prune each of them. I’ll also touch on why you might not have a lot of flowers.
Before we begin breaking down each type of Hydrangea, let’s discuss flower buds because this is what confuses so many people and will dictate the care each Hydrangea will receive and when. Unlike many other plants, Hydrangeas flower either on new wood, old wood or a combination of both old and new wood. What does this mean? A Hydrangea that flowers on new word means that the flower buds are created (or set) in the current garden season. A Hydrangea that flowers on old wood means that the flower buds are set during the previous growing season. There are newer varieties of Hydrangea (plants purchased within the last 20 years) that flower on both old and new wood.
Hydrangea paniculata varieties. (Panicle Hydrangeas). We’ll start with the best, or at least the best selection for Connecticut gardens in my opinion. Why would I say that? Well, there is a big difference between Panicle Hydrangeas and most other types of Hydrangeas. They are 1 of 2 Hydrangea families where 100% of their buds form on new wood. Because of this, flower buds can’t be damaged by a cold winter. Flower buds are set during the current garden season. When flower buds are set in the current garden season, you can control height in the fall or even in early spring. As a busy landscaper, I love the long pruning window. Heavily pruning these varieties in spring or fall will actually encourage more flowering. Don’t worry about pruning away too much of the plant if you prefer. These plants care take it. Hydrangea paniculata varieties are the easiest Hydrangea to maintain because of the long pruning window and are the only consistent flowering Hydrangea in Litchfield County. A lot, but not all, flowers on Hydrangea paniculatas are cone shape. All Hydrangea paniculata start white and many fade to a mauve or pink color.
Hydrangea serratas (Lacecap Hydrangea) aren’t a bad choice for Litchfield County gardens. Most flower on new wood but their are some newer varieties like ‘Tuff Stuff’ that do produce some flower buds on new growth. Generally, I feel like Hydrangea serrata are more consistent than Hydrangea macrophylla in Litchfield County when it comes to flowering. Because most flower on old wood, Hydrangea serratas should only be pruned after flower in summer. If you notice any dead or damaged branches in spring, those branches can be removed because those branches won’t produce a flower. Even if you have a newer variety that flowers on old and new wood, it’s recommended you on;y prune after flowering because you’ll still have old flower buds on the plant.
Hydrangea arborscens, or Smooth Hydrangea, is the other family of Hydrangea that flower on new wood. We like that! That means the care of Hydrangea arborscens is the same as Hydrangea paniculata. Prune in fall, late winter or early spring to control height and promote flowering. We often will cut them to the ground to promote a lot of vigorous growth which will help with flowering. Hydrangea arborscens are native to CT and the Eastern United States so that’s super cool! We always love when we’re planting plants that are aesthetic pleasing and our native to Connecticut. Planting natives is so important to promote wildlife and combat habitat loss due to development. The one issue, if you want to call it an issue is in it’s native range, Hydrangea arborscens are found under the canopy of other trees where moist soils exist. This plant does not like to be dry. Take that into consideration when choosing a location. It prefers part shade too but as long as it has moisture, it will do fine in sun. Identification between this plant is a little difficult when comparing it to Hydrangea macrophylla. Both families have varieties with white flowers and the flower shape are sometimes similar. Using the leaves as an identifier is probably easiest. In general terms, Hydrangea arborscens leaves are thinner and less shiny when comparing it to Hydrange macrophylla.
Hydrangea quercifolia, or Oakleaf Hydrangea, are easy to identify because of their leaves. Oakleaf Hydrangeas flower on old wood so the only chance you have to prune them is right after flower in summer. I mean, you can prune Oakleaf Hydrangeas, or any other Hydrangea that flowers on old wood, at any time during the season. You’ll just lose your flowers for next season if you prune outside the recommended time frame. Oakleaf Hydrangea are not native to CT but they are native to the eastern United States mostly found in the southeast. As with any Hydrangea that only flowers on old wood, you’ll have some good years and you’ll have some years you might only have 1 flower. Unfortunately, that’s life in Litchfield County.
Hydrangea macrophylla, Bigleaf or Mophead Hydrangea is the Hydrangea everyone things of when they think Hydrangea. It seems that everyone has a memory from Cape Cod, Martha’s Vineyard or the Hampton’s that involves this plant. Unfortunately, Hydrangea macrophylla don’t consistently flower in Litchfield County. Interestingly, this picture was taken in one of our gardens this year. I’ve been in the landscape business for over 40 years and I can’t remember a better season for flowering plants. Why is that? The reason this year was so incredible for Hydrangeas and other spring flowering plants is due to the mild winter. A mild winter means less damaged flower buds. Also, these are Hydrangea ‘Endless Summer’. Some Hydrangea macrophylla flower varieties are affected by the Ph of the soil. The more acidic the soil, the bluer the flower, the more alkaline the soil, the more pink the flowers will be. A neutral soil Ph will produce a white flower. In the above picture, notice how some of the flowers are blue and some are pink? A lot of older Hydrangea macrophylla flower on old wood but there are a lot of varieties that flower on both old and new wood. If you don’t know what variety you have, the only thing you can do is do some experimental pruning. I would suggest you prune some plants heavily in spring and only remove dead or damage branches on others and see what happens. If the heavily pruned Hydrangea produces any flowers, it’s either a newer variety macrophylla or if it flowers a lot, and the flower is white, it could be a Hydrangea arborscens (remember, they’re hard to tell apart).
