Answer: Theoretically, peonies bloom over about a seven week period. Unfortunately there is no standardized classification system for which specific varieties would be early, mid, or late season bloomers. You might find the data from the following web site helpful however. The peony bloom project has tried to create a list of cultivars and show their bloom time in relation to the variety "Red Charm". Here is the general link to their site,
and the chart showing relative bloom times of the cultivars for which they have data so far.
You could compare the peonies you like to the dates on the list to make your selection.
Or, you could go back to the nursery and ask one of the professionally trained staff to make a selection for you from among the varieties they have in stock. There are so many lovely peonies on the market that you are sure to find a selection to help extend the bloom dates in your garden. Best of luck with your project!
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