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I think peonies are fairly easy to grow and they are fairly resourceful plants but one issue I have had in the past is with peonies not flowering. When I say not flowering, this can mean a lot of things from buds never actually forming, buds not opening or simply the buds drop off before they open.
I think the most common problem is that the buds actually never form. Now for me, I quickly learnt that I had planted them too deep which resulted in lots of foliage but no flowers, not even buds. However, this is not the only reason for peonies not flowering so here are the most common reasons why peony flower buds may not develop or why they may not open fully starting with what I think is the most common reason, they were planted too deep.
Peonies are planted too deep
The crown (top) of the root ball of a peony should be between 2.5cm and 5cm below the ground, so literally just below the surface. Any deeper and the dormant buds may not be able to find their way up through the soil into the open. Not sure why this is the case but for most people, this is probably the issue. This is even more so if you plant rootstock (just the root with no soil) as people have a tendency to plant them deep. You will still get lots of foliage but for some reason, those flower buds wont develop.
Bud Blast (Buds develop but then stop forming and never open)
Anything – environmental or climate – that stresses the peony plant might result in what is known as ‘bud blast’. Bud blast is where the flower buds develop but fail to open, this is actually fairly common. Many of the reasons below result in this condition and it can be caused by lots of things from an early winter frost damaging the buds to fungus attacks from fungus such as Botrytis blight.
Cold in the spring time
Suffering through a cold snap in the spring affects your peony plant’s development of buds. You won’t know this has happened until later on when the bud turns brown and falls off. There is not much you can do to avoid this, maybe cover with fleece if a cold snap is forecasted. I usually take my chances but I grow my peonies in a fairly sheltered position where they are at less risk.
This is a fungal disease that shows up as a grey mould. It usually affects the leaves and new shoots of peonies. But it can also turn young flower buds brown and cause them not to flower. Once the flower bud has this problem, remove it from the plant – it can’t be saved. I usually spray my peonies with a fungicide at the first signs of disease to try and help prevent it.
Not enough sun
This is probably more common than you might think, along with planting them too deep. Peonies need at least six hours of full sun every day to get the most out of them. This amount of sunlight is especially needed in the spring when the plant is in full growing mode. Tall plants around them may throw peonies into the shade. Walls and fences may also put them in shadow. This can lead to the buds not forming in the first place.
Too much competition from surrounding plants
Competition from surrounding plants is for sunshine, and also for water, nutrition, space and fresh air. Peonies need space around them to ensure good air circulation within the plant, this also helps prevent mildew which peonies can get. These also need adequate nutrition from well-composted soil and fertiliser. And don’t forget to water them often, especially in times of drought.
While peonies aren’t greedy plants for any of these elements, they do need to get their fair share. I actually overcrowded one of mine this year with bedding plants and its not never got going because of it.
Too much nitrogen in the fertiliser
An excess of nitrogen in the fertiliser you give your peonies encourages foliage to grow. You’ll have lush and very green leaves but minimal or no flowers. Nitrogen puts all the plant’s energy into growing leaves and there’s nothing left for the development of buds and flowers. This is a common reason why peonies aren’t flowering but this is also the same for many plants. I recommend just using a feed that is high in potash once they develop buds or feed with a general feed in spring.
Cut back before next year’s buds form
A peony plant starts to create buds for next year’s blooms in the autumn. For this it needs food from the soil and energy that comes into the plant through the leaves. If you cut your peony back too early, there are no leaves left to produce the energy needed. This limits how many buds can form and their quality.
Cut back your peony plant in late autumn. This is also the time to transplant or divide them as well.
Immature or divided plants
Maybe your peony is too young to develop flowers. A new peony needs at least two growing seasons in which to become established and settle in before it flowers. The same is true of any peonies that are from divided plants. If you but root stock with only a few eyes on or small plants grown in pots, these may not flower the first year so be a little patent.
What to do
Most of the reasons as to why peonies aren’t flowering have environmental causes. You can generally easily fix them. Once they have finished flowering, check out this guide on what to do with peonies after flowering and you can also read why your peony is wilting.