Hydrangea Care in May

Hydrangea Care in May

Knock on wood and cross your fingers, but it looks like a good flowering year for our mophead and lacecap hydrangeas! Because we had a fairly mild winter, most of the flower buds that these shrubs formed in the late summer of 2019 lived through the cold season. All of those small green leaves you see forming on your hydrangea canes now should develop into foliage and flowers.

Here are the things you can be doing for your hydrangeas now, plus some tips on buying new varieties to add to your landscape.

  • If you haven’t pruned your mophead or lacecaps (Hydrangea macrophylla and Hydrangea serrata) yet, you can do so now. We often have to wait until late May to see what’s living and what’s dead, but this year the plants are leafing out early. So get out with this in mind: don’t cut off any canes with green leaves or buds on them. It’s impossible to make them shorter since they will replace their height by mid-July. (All those green new shoots you see at the base of the plant will grow to be the same height.) Just cut away tips with no live buds, or canes that are bare with no leaves at all.
  • If your hydrangea is too large for the location, move it now. Early May is a good time to do this. You can split plants now too, if you want to make more.
  • Fertilize with Holly-tone for blue hydrangeas, but use Flower-tone for pink or white varieties.
  • Top dress around older plants with one bag of compost per shrub, spreading it out to just beyond the drip-line.
  • Top the compost with an inch of mulch. This helps keep weeds down and the moisture in the soil under your plants.
Clip off old flowers and any bare canes that have no leaves or green buds. If you have a plant with buds that are still black and green, leave those to see if they might open later in the month. If they haven’t turned into green leaves by the end of May, cut that cane out.
This is a hydrangea before it is pruned. It is ready to have some Holly-tone, then compost spread around the plant, topped by an inch of mulch.

Buying New Hydrangeas

Our nursery has just begun to get in shipments of hydrangeas. The majority of these will arrive later in May and we’ll continue to get them in through the summer. So don’t feel pressured about finding the right plants immediately, because there is plenty of time for shopping and planting these Cape Cod favorites.

  • Look for hydrangeas that will be the height you are looking for, since it’s impossible to have a good amount of flowers and prune them shorter. Trying to control a shrub’s size by pruning is a make-work project for the homeowner, and for the mophead and lacecap varieties it doesn’t work anyway.
  • If the area where you want to plant is in full sun, good choices would be any of the panicle types (Hydrangea paniculata) that have white flowers from late July into fall, and often turn pink as they age. When planted in full sun the blue hydrangea flowers brown out by mid-August.
  • Mophead and lacecap hydrangeas do best when planted in locations that either get morning sun or late-afternoon sun, but are shaded between about 11 AM and 3 PM.
  • Various smooth hydrangeas (Hydrangea arborescens) such as Annabelle do well in sun or shade, but the pink varieties grow best when in full to half-day sunshine.
Hydrangea flowers that are in full sun will brown faster than those that are shaded from 11 AM on. If your blue hydrangeas are in the full sun they will probably wilt every day it’s hot, even if the soil is wet. This constant wilting causes the flowers to go by faster.
This photo shows both types of hydrangeas. The blue flowers are Endless summer, which are pruned as second year bloomers even though they produce some flowers on new growth later in the summer. The largest flowering on Endless Summer is on second year growth so that’s how they are treated. The white flowers in this photo are a Hydrangea arborescens. It is a new growth bloomer and although you can cut it back and still get flowers, the more you prune it the more likely that the big white blooms will fall into the mud every time it rains. Older canes are sturdier.
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