All about peony bloom date ratings, week by week

When visitors stroll through the tables of potted peonies we have for sale there is a common question… What do the bloom week ratings mean?

Here’s my answer. The long version.

When plants are labeled as blooming early, mid-season, or late, there is a lot of opinion and variation that goes into those classifications.

Instead, so we can all be on the same page, peonies are given a bloom date rating. These ratings are expressed in the form of weeks that start at one and continue to eight.

The start of week one all depends on where you are growing your peony. Folks in the south have week one as early as late February or early March. Here on our farm week one is typically in early May.

But bloom date ratings can even vary between much closer distances and even withing microclimates. Peonies on a southern wall exposure will bloom earlier than the same variety just a mile away in a sunny valley where the cool air pools.

But all bloom date ratings have one thing in common. They are all measured off when Peony Red Charm blooms. Red Charm marks the start of week four in the bloom date ratings.

The American Peony Society and its members have submitted and collected mountains of data of hundreds of peony varieties to amass a central source of bloom date ratings, called the Bloom Date Project.

Weeks four through six have the largest selection. Both earlier and later, there are fewer varieties that bloom.

Coral and red hybrids make up the majority of week four. Pink varieties tend to follow for week five. Finally, white and blush varieties dominate week six. There some crossover here with outliers and rulebreakers, but you can think of this as a general guideline.

Why do we care about bloom date ratings?

If you are looking for one mass peony bloom where all your plants peak at the same time, you should collect varieties that all have the same bloom week. On the other hand, if you want to extend your peony bloom season to six week or more, you’ll want to select varieties from different bloom weeks.

There’s no right or wrong answer, but rather a personal preference.