How to Harvest & Store Peonies: A Grower's Guide from the Alaska Peony Cooperative

Nothing quite captures the feeling of perennial season quite like the queen of spring blooms: the peony. Peonies are an incredibly rewarding crop for a flower farmer to grow - they're stunning focal points to every bouquet, and they have a loyal following at every market. 

But every flower grower also knows that they're a serious investment. Years of establishment, a narrow harvest window, and plenty of hands-on labor mean that every stem counts. 

No one understands this better than the growers of the Alaska Peony Cooperative. With decades of collective experience in Alaska's unique climate, they've built deep expertise in what it takes to bring exceptional peony stems to market. This post was written in collaboration with APC, who generously shared their expertise, knowledge, and resources. It's a bit more lengthy than usual, but we had a lot to share. So, grab a cup of coffee, pull up a chair, and dive into the world of peonies with us!

Disclaimer: This post was written in collaboration with Alaska Peony Cooperative based on their experience. The advice shared in it is not a Rooted endorsed guide but rather a suggested approach advised by a successful grower in the Rooted community.

What We’ll Cover:

1. Harvest practices
2. Grading practices
3. Processing practices 
4. Storage tips

Keep in mind that handling peonies can vary by variety, so treat this post as a starting point and get to know the nuances of each variety in your fields. Let’s jump in!

Photo Credit: Alaska Peony Collective

Step One: Harvest at the Right Stage

Alaska Peony Cooperative has found that cutting each variety at the correct stage is the foundation of successful post-harvest performance. We'd like to note that before starting, always be sure to have clean tools – sanitize and disinfect snips and buckets to prevent the spread of disease. 

APC has created their flowering stage definitions, as seen below, by pulling from their own experiences and by referencing a vase study guide¹ created by a 2020 graduate student at UC Davis in collaboration with the Alaska Beauty Peony Coop team. We'd like to note that this study is not a piece of peer-reviewed research. However, the study was completed with a variety of players in the Alaska peony market and it has become a helpful resource for some growers. 

APC Flowering Definitions:

• Stage 1: Marble stage; firm bud, showing color yet but not yet opening
• Stage 2: Colored bud; slightly larger bud size, showing more color and beginning to soften
• Stage 3: Marshmallow stage; showing more color and is softer

APC notes that a Stage 1 or 2 bud generally gives you the longest storage window – up to six weeks. They also note that anything cut at a stage 2.5 or softer should have a three-week maximum storage window to maintain quality and reliability.

Note that these definitions serve as a rough guideline, as every variety has its own unique perfect harvest stage and must be cut accordingly. As an example, APC notes that while cutting Duchesse De Nemours at stage 1 or 1.5 is the perfect stage for that variety, cutting Elsa Sass or Dr. F.G. Brethour at any stage earlier than stage 3 will result in a bud that never fully opens. 

Growers should keep in mind that harvest stage is a combination of the look and feel of the bud. APC has found that the proverbial “marshmallow stage” is not the correct harvest stage for many varieties – they say that many should actually feel more like a ripe avocado or mango. A guide published by the University of Alaska, Fairbanks provides some suggested bud stages for harvesting per variety, you can view it here.

Step One, Continued: Peony Bud Grading & Setting Standards 

Importantly, peony grading is distinct from bud/flowering stage. A bud harvested at the correct stage (as outlined above!) for its variety can receive any grade, based on quality factors and grading standards. Peonies are graded after they are harvested, and the grade informs pricing.

It is also noteworthy that according to the guide published by the University of Alaska, Fairbanks², despite the USDA publishing guidelines on peony grading, standards are largely ignored. Most growers develop their own internal grading systems, as APC has. 

The Cooperative has combined standards from the USDA, New Zeeland, and Alaska programs. They have taken the "best grades of all systems" and apply them to their own approach. They shared that the USDA is more concerned about stem length while New Zeeland guidelines are more focused on bud diameter, so they pull from each to provide customers with the best product.

The image above depicts the diameters that APC uses - also outlined below:

• Grade AAA Buds:  ~45mm in diameter; premium grade
• Grade AA Buds:  ~40mm in diameter; premium grade
• Grade A Buds:  ~35mm in diameter; standard grade
• Petite Peony:  ~35mm in diameter; petite grade

It is worth noting a different example of grading standards, which can be seen in Peonies as Field Grown Cut Flowers in Alaska³. Growers can follow the approach of APC and create their own standard for grading, or follow guides such as the two shared here. 

APC has also taken a different angle on the premium vs. standard naming convention by 1) combining both grade AAA and AA into "premium" given that they are both large and 2) reframing "seconds" to "standard" for marketing purposes. 

Step Two: Process Quickly and Cleanly

APC knows that proper processing protects their stems from disease, ensures quality and consistency, and sets them up to easily fulfill orders for buyers. These processes are what APC has found works for them, but it is important that growers decide what will work best for their team and location. 

The APC team does not feel that a fancy set up or complicated equipment is necessary, but they do find that a covered area is important to their processing procedures. They note that processing as soon as possible after harvesting is very important – they aim for within 30 minutes. 

Alaska Peony Cooperative Processing Steps:

1. Remove all leaves except the top two or three leaf sets
2. Grade to standards
3. Dip in diluted bleach water and vigorously shake off the excess
4. Let dry on racks with fans and pat dry with clean towels
5. Bunch in by preferred count
6. Trim to final stem length
7. Count for inventory before moving to the cooler
8. Label shelves by variety, grade, and harvest date
9. Move product to cooler

APC noted that their bleach dip does two important things: it rinses off the sticky sap that can lead to sooty mold, and it slows the spread of botrytis⁴  in storage. It won't eliminate mold entirely, but it makes a meaningful difference over weeks of storage. They use a ratio of 1 tablespoon of bleach per gallon of water. Be sure to use gloves and safe handling practices whenever handling bleach or other irritants.

That said - according to APC, open buds and specific varieties (e.g. Henry Bockstoce, Elsa Sass, Shirley Temple) should not be fully immersed in a bleach-water solution. Instead, they suggest using a wipe with the solution to clean off as much sticky sap as possible from the buds and stems before placing in the cooler.

Once the product goes into the cooler, leave it there until it goes to the customer. Consistent temperature control is important because fluctuations in temperature can cause condensation, which leads to mold, and will shorten the vase life.

Step Three: Cold Storage 

Temperature and Humidity

APC has found that optimal storage is 32–34°F (0–1°C) with 75–80% relative humidity and as little fluctuation as possible.⁵ Although the flowers should be stored at high humidity, they need to remain dry to reduce the likelihood of development and spread of disease, like Botrytis.⁶

Cooler Conditions

Make sure the cooler is clean and sanitized with the diluted bleach solution before and throughout each season. APS suggests avoiding storing peonies directly under a vent, under a fan, or right near the door to reduce temperature fluctuations and possible desiccation. 

They also share that dark-colored peonies (e.g. Red Charm) show cooler damage more easily than lighter varieties. The APC team has found storing them in the center of the cooler, away from vents, fans, and the door prevents ice crystals from forming on the buds and damage due to people bumping into them.  

Dry Storage

Unless processed peonies are going straight into an arrangement or to the buyer immediately after harvest, peonies often perform best if stored dry.⁷

To store peonies dry, APC says that you can stand them up in buckets, about 50–80 stems per 5-gallon bucket, or 250–300 stems per large tote. They note that one exception to this is the Red Charm variety which should lay flat in the cooler for 24 hours first.

APC shares that flat storage is also a great option for maximizing cooler space. Large floral boxes can be used for this. Stack the stems in alternating layers with buds facing outward like a stack of logs. 

If using a rack with a metal grate as shown below, line it with cardboard to prevent the grid lines from pressing into the sides of the buds. APC has observed that stacks can typically reach up to two feet tall without damaging the bottom layer, and this method will keep leaves hydrated and plump. They say that any variety that has been cut firm should work well in this style. They also suggest avoiding wrapping stems in newsprint or paper as ink can transfer to the stems and can stick if there is any sap left on the stems.

Additionally, they have found that open bloom forms (e.g. Henry Bockstoce) or soft cut stage varieties (e.g. Elsa Sass, DR F.G. Brethour) may store better standing upright in buckets to prevent smashing the softer buds.

Labeling & Organizing

APC has also developed a labeling system that keeps their coolers organized and product moving in and out at the appropriate times. They label by shelf and by side of the cooler. 

To the left in the cooler is grade A (standard) and to the right are grades AAA and AA (premium). Each shelf then holds a different variety. As an example, they would have the right bottom shelf as Boule de Neige AA and AAA and left bottom self would be Boule de Neige A. This always stays consistent so that everyone is clear and stems can be stored and packed by anyone on the team. This is the most important takeaway from their system - make sure to stay consistent. 

As previously mentioned, everything is processed straight out of the field prior to storing in the cooler. Stems are graded, leaves stripped, cut to length, cleaned, sanitized, and bundled into bunches (they do 5 stems each). They then take them to the cooler and use their inventory system to log the count. 

Timing

Storage time can vary depending on the temperature of the cooler, variety, and harvest stage, but APC offers a few general guidelines:

1. A stem cut at Bud Stage 1 or 2 can be stored for 6 weeks without compromising vase life or quality
2. Any variety cut at Bud Stage 2.5 or softer should only be stored for 3 weeks for maximum reliability
3. Bloom form matters – Semi-doubles and single bloom forms tend to store for less time than full double and bomb bloom forms. 
4. Coral peonies do not do well in extended cold storage
    

A Final Note

Taking the time to get harvest and post-harvest handling right is one of the best investments you can make as a peony grower. Better quality blooms, longer vase life, and happier customers; it all starts in the field and follows through to the cooler. 

Special thanks to Martha Lojewski of APC for the detailed information and resources for this post. Learn more about the Alaska Peony Cooperative here. Wholesale and retail buyers can  shop for their premium peonies on the Rooted Farmers platform June - August.

References

1. Lourie, A.P (2021). Vase Life Study Harvest Guide 2020.
2. University of Alaska, Fairbanks. (2008). Guide to Peony Production. UAF Cooperative Extension Service.
3. Alaska Peony Growers Association. Peonies as Field Grown Cut Flowers in Alaska. American Peony Society.
4. University of Missouri Extension. Botrytis Blight of Peony. MU Plant Diagnostic Clinic.
5. Armitage, A.M. and Laushman, J.M. (2003). Specialty Cut Flowers, Second Edition. Timber Press.
6. Byczynski, L. (1997). The Flower Farmer: An Organic Grower's Guide to Raising and Selling Cut Flowers. Chelsea Green Publishing.
7. Byczynski, L. (1997). The Flower Farmer: An Organic Grower's Guide to Raising and Selling Cut Flowers. Chelsea Green Publishing.