Folks, sometimes we just hit learning curves. Sometimes those learning curves are steep.
That was us this Spring. Specifically we learned what happens when peonies expeience hard frost in late May.
Here’s the background.
Our last frost usually happens sometime during the first 2 weeks of May. But not this year, Friends.
This year we had an unpredicted 25F (possibly colder?) frost right at the end of May - exactly when we’d normally be starting to plant out warm weather crops like tomatoes and zinnias.
And the frost damage in our peony fields was unlike anything we’ve ever experienced. It seemed like everywhere I looked I saw damage. I even wondered if perhaps I was being dramatic and exaggerating the extent in my mind.
But during the America Peony Society (APS) tour, Nate Bremer - head of APS - said he'd never seen such extensive frost damage as what he saw in our fields this year. Guess I wasn’t being dramatic.
Here’s the damage
The first thing I noticed was bud blast. Overnight probably 80% + of our herbaceous (both hybrid and lactiflora) lost all or most of their buds to blast.
But the blasted buds were just the beginning of the story. Some of our younger, more exposed tree peonies died back to the ground. And we immediately found loads of twisted curling leaves on our herbaceous peony, particularly on the North and West sides of the plants. (Our prevailing winds are generally North Westerly here).
Then over the course of the growing season, the true impact of the hard frost emerged. Peony Leaf Spot (graphiopsis chlorocephala) developed at points where peony foliage had sustained frost damage
Peony stems that were previously straight twisted and contorted so much that in extreme cases some buds were blooming at a near 90 degree angle to their stems.
We also noticed abnormalities as seemingly unaffected buds bloomed.
In one particularly exposed section of our fields, some buds showed no external damage but - when the flower opened - brown spots were easily visible on the petals.
Additionally on some varieties we found that sections of the guard petals or outer portion of the bloom were either deformed or missing entirely
Worst of all, some damaged buds developed botrytis (which we made sure to remove as soon as we observed it).
Here’s how we responded
We immediately removed all blasted buds
We kept an extra sharp eye out for botrytis damage and immediately removed anything suspicious
We removed all severely damaged foliage and are continuing to do so throughout the growing season.
We’re removing any twisted stems as these damaged tissues are susceptible to disease development. This process is still ongoing.
We did extensive foliage disease testing to ensure we didn’t have any more serious issues such as extensive botrytis or foliar nematodes. (Tests confirmed we do not).
We stopped all peony cut flower sales (as we couldn’t guarantee even healthy looking buds would open as healthy flowers)
Here are some takeaways and resources in case this happens to you
First, fight the good fight wrt damage foliage/bud/bloom removal.
We recommend taking all the removal steps we highlighted above. Further, in years where heavy damage like this occurs, exercise extra diligence in your Fall Cleanup. Make sure all peony foliage is removed and either put in the trash or burned.
Second, test the foliage
If you’re seeing extensive disease you’re going to want to confirm you don’t have more serious issues like botrytis, phytopthora or foliar nematodes. We’ve had great experience with the Cornell Plant Disease Diagnostic Clinic. They are extremely knowledgable, responsive and affordable.
(If you’re not in NY State, you can still use the Cornell Clinic. The prices are a bit higher but still reasonable. You might also see whether your own State’s Landgrant/Extension system offers a similar service),
Thirdly, remember your peonies will likely make full recovery.
Despite everything our peonies went through, they are now looking quite healthy - even the 1500+ we moved last year. We do not appear to have sustained much if any long-term damage.
Finally - and most importantly - remember this isn’t your fault.
Unless you start growing in structures, plant and flower damage is simply going to happen if you get a late, hard frost. If it happens and you take all the responsible steps listed above, you can rest assured you’ve done your best.
In closing - I know it can be hard to find detailed info on peony frost damage and diseases. So if you have any questions I didn’t address above, don’t hesitate to post in the comments. I feel like I am learning all of this as I go so - even if I don’t know the answer - I’ll do my best to point you in the right direction.
What a year to invite the APS to your farm! This was a very helpful post for me because I hadn't connected the weird looking flowers and extra disease to freeze damage. I figured the disease was because of the plentiful rain. Haven't done a speck of disease/damage trimming but I guess I should put it on the list. There's always more to do than there is time to do it all. At least I don't depend on my peonies for income!