We’ve been harvesting, storing, and selling fruit and nut pollen since 1933. In that time we’ve learned a lot about how to store it and maintain viability for as long as possible. Our methods have progressed from Great Grandma Mina Firman’s root cellar canning jars in the 1940s to today’s commercial freezers with temperature alarms and backup power.

Pollen stored properly will maintain viability (+90%) for at least 5 years. We’ve confirmed that with thousands of viability tests conducted in our Yakima lab over the years. As part of our Certified Premium (https://firmanpollen.com/certified-premium/) process each lot of pollen (segregated by field, date and variety) is sampled every 6 months and germinated in a petrie dish filled with agar growth medium. We allow the pollen to grow for 12 hours at 70 degrees and then count what percentage of pollen grains are viable and growing. We document the results, and if viability falls below our standards, we dispose of that lot.

C.E. (Gene) McClure’s Peach Pollen – Harvested 1988

Deep in the back of one of our freezers, our oldest lot of pollen is marked by a handwritten note from my Grandfather Gene McClure – “Red Corah Peach.” We don’t sell or harvest all that much peach pollen these days, but grandpa passed down an unintended experiment that we open and test every now and then to see just how much viability pollen retains after extremely long-term storage. Even after almost 40 years of storage, 40% of the pollen grains in this lot of pollen germinated in our lab this spring.

“Red Corah” Peach Pollen from 1988

37 year-old pollen, 40% viable

10 year-old pollen, 90% viable

1 year-old pollen, +90% viable

Pollen Storage Tips for Growers

In-season Storage

Long-term Storage

The way Washington fruit growers apply supplemental pollen to cherries, apples, and pears is changing fast.

Eight years ago in 2016, Zirkle Fruit made the first commercial application with our liquid Precision Pollen system on cherries. It used electrostatic sprayers it had purchased for blueberries. Few fruit growers in Washington had spray equipment for liquid pollen at the time. Just eight years later in 2024, ⅔ of the pollen we sold was Precision Pollen for electrostatic spray application.

The ongoing transformation has taken a lot of hard work and investment from partners and customers. It’s happening faster than we even imagined.

Key reasons we think more growers are adopting Precision Pollen liquid application:

WSU trials and field success

Cornell University research proved supplemental pollen’s value in the 1920s. Then innovation crawled incrementally for about 100 years. We knew the tank mix solution (to extend pollen lifespan in water) and purified sprayable pollen we developed with Dr. Matt Whiting at WSU in 2014 had to be tested and proven. The Tree Fruit Research Commission funded the work, and positive results ignited interest in electrostatic spray-on pollen.

Key research highlights:

• Fruit set increased vs natural pollination in 13 of 16 cherry trials from 2014 to 2021 – most in the range of 20-40%
• 3X more pollen grains were deposited on blossoms’ stigmatic surface by charged-particle electrostatic sprayers vs natural pollination

Additionally, growers are seeing electrostatic pollen pay off in their operations with more consistent production and quality. Some of the most common uses are lighter producing cherry varieties, and high-value hard to set cherries like Early Robin, Orondo Ruby and Regina. In apples, Cosmic Crisp growers have found it helps fight excessive drop and sets more doubles when desired. In young blocks, growers are spraying pollen as they establish pollinizers and learn about their compatibility and effectiveness.

Equipment innovation and investment

Electrostatic sprayers’ small particle size, wraparound coverage, and efficiency are kind of magical for pollen application. They weren’t widely used in Washington in 2013 when we started development of sprayable pollen.

As manufacturers identified opportunities in orchards, they adapted equipment used in vineyards, berries and other crops. Fruit growers recognized benefits for all kinds of spray applications (chemical savings, labor savings from fewer fills, improved coverage) and have been deploying more of the sprayers every year.

Mark Ryckman, co-owner and sales manager of the California company that builds Lectro Blast sprayers, said he’s seen adoption rates snowball over the past decade. In the last five years he’s sold almost 200 sprayers to Washington fruit growers, compared to about 50 in the five years before that.

“We’ve done a lot of coverage demonstrations in orchards with a blacklight test, and it’s very convincing,” Ryckman said. “When pollen came on a few years ago it was another great use for our sprayers. It was part of really getting things rolling.”

Precision control and measurement

For every input, growers are seeking more measurement and control. When counting buds and managing cropload, tighter control of pollen application becomes more critical. We hear from and advise growers each year as they dial in their pollen program by block, variety, rate, number of applications, bloom stage, temperature and even humidity.

Electrostatic spraying puts more pollen directly on the blossom’s stigmatic surface, giving growers the most control of any currently available application method. Until we can train a bee, or tell a robot exactly which blossoms to target and when…

For more information about Precision Pollen and electrostatic application, go to:

WSU research trials results – https://firmanpollen.com/grower-resources/

Electrostatic application instruction video – https://firmanpollen.com/precision-pollination-system/#single/0

Progressive Ag LectroBlast sprayers information – https://proaginc.com/

It’s one of the most common challenges we hear about each spring: “I’ve got a block of ___________ (Early Robin, Skyler Rae, Orondo Ruby, Tieton, Regina, Benton – fill in the blank) cherries that I can’t get to set consistently.”

Planted for quality characteristics and harvest timing, these varieties can command high prices. But poor production has driven many orchardists to frustration, chainsaws, and grafters. Researchers studying the problem and growers who continue to nurture these blocks to profitability acknowledge it’s a battle.

“The limiting factor (in these varieties) is the short lifespan of the ovule,” said Dr. Matt Whiting of WSU. “In some cases you have just a very small window of opportunity to set fruit.”

That window is called the effective pollination period (EPP). EPP = Ovule viability time from bloom opening – (time for pollen adhesion + germination + tube growth down the style). In 2018, Whiting and his research partners Lu Zhang and Louise Ferguson found that at 64 degrees fahrenheit (near average bloom temperatures) ovules remained fully viable for 3-4 days in high productivity varieties like Rainier and Sweetheart, and only one day for low-productivity cultivars like Tieton and Benton. They decay from there. After 7 days with temperatures under 75 degrees, 80% of Rainier ovules were still viable, but only 30% remained so in Tieton, Benton and Sweetheart.

It takes at least 48 hours for any cherry pollen at any temperature to germinate and grow to fertilize the ovule. That’s why short-ovule receptivity, low-productivity varieties often set less than 10% of blossoms, while high productivity varieties can set as much as 70% of blossoms. It also helps explain why some cold springs (like 2022 when it snowed on bloom) result in better fruit set for low-productivity varieties. Low temperatures (Low 40s to mid 50s) extend ovule viability considerably and don’t slow pollen tube growth to the same extent.

Grower Strategies

So, when there’s only a short period of time to get pollen to the stigma, what options do you have? There’s no magic bullet, but we’ve worked with growers who’ve improved success rates by using some or all of these tools.

1. Ensure pollinizer bloom quantity and overlap
2. Place more bee hives in block
3. Apply supplemental pollen repeatedly as bloom opens
4. Spray plant growth regulator to buy just a little more ovule viability time (most effective in warm years)

Trial and Success in Orondo

Griggs Farms in Orondo has applied supplemental pollen to its Orondo Ruby blocks with electrostatic sprayers longer than just about any other grower. After experimenting with different rates and timing, they’ve refined their program the last few years and achieved good results and more consistent production.

“What we’ve had the most success with is having as many applications as we can as the bloom opens up,” said Sam Gwinn, a manager for Griggs. “We’re creating more pollination events closer to when the flowers open, just increasing the chances of actual pollination.”

Gwinn said field consultants have advised that there may be as little as 15-20 minutes to get pollen to the stigma in warm, windy years, “and obviously more time when it’s cooler.” They begin applying at 10-15% bloom, and then apply again as another 10% of bloom opens up to about 70%. In total, they’re aiming for six applications. With each application, they apply 15g/acre and drive every other row of their high-density, trellised plantings.

This year, all of those applications happened in two days. A warm-cool-warm weather pattern resulted in a near flash bloom with temperatures going from 40s to 70s overnight.

“We started really early in the morning and finished really late. We just kept going (as the bloom opened throughout the day),” Gwinn said. “We’ve had a lot of success spraying at night. We think it’s a little cooler, maybe a little moister.”

Although the weather conditions were very different, 2022 (snow on bloom) and 2024 (flash bloom in warmer temps) were two of Griggs’ best Orondo Ruby production years. The attention to fruit set and pollination is a strategic investment of time and money. Griggs doesn’t spray pollen on other cherry varieties that are highly productive without the extra expenditure.

Gwinn said they’ve tried and abandoned spraying ReTain and another plant growth regulator after seeing little impact, and also determined that pollen on beehive inserts wasn’t highly effective for Orondo Ruby. They have grafted more pollinizers into their orchards to provide additional pollen and hopefully set even more fruit.

Other Application Methods and Experimentation

A number of other Firman customers dust their short ovule receptivity cherry blocks with pollen. From what we’ve heard, the most successful approach mirrors Griggs’ experience in Orondo with applications each day – and sometimes multiple times a day – to cover the bloom as it opens. Some growers also add pollen to beehive inserts or mix in helicopter applications to improve their odds of setting more fruit.

We’ve planted our own Regina and Benton cherry blocks west of Yakima with the primary goal of harvesting blossoms and pollen. But, we also grow a cherry crop and use the blocks to try new pollen application ideas. Last spring, we hit our Regina bloom frequently with electrostatic spray application and also upped the amount of pollen in each tank. We’d seen some promise in higher rates in WSU trials and thought Regina might be the right place to try it again. The results were promising, and we’ll be experimenting this year to learn more.

It takes a ton of diligence, attention to detail, and sometimes a little luck with weather to pollinate financially viable crop volumes in these cherry varieties. We’re here to help and support growers however we can.

Research Reference

Zhang, Lu; Ferguson, Louise; Whiting, Matthew D. (2018). Temperature effects on pistil viability and fruit set in sweet cherry. Scientia Horticulturae, Volume 241 (18 November 2018), pages 8-17.

https://www.sciencedirect.com/science/article/abs/pii/S030442381830431X

Markets continue to raise the bar on requirements for fruit quality. Without question pollination plays a significant role in fruit quality in apples and pears. Understanding the process is key to making decisions about pollinizers and supplemental pollen to help maximize the quality in each orchard.

Good Pollination = Good Fruit

All five stigmas pollinated

Large, well shaped fruit with all 9-10 seeds developed

Not all stigmas pollinated

Smaller, misshapen fruit with less than 9 seeds

Flower Anatomy and Fruit Development

Apple and pear flowers have the following female reproductive parts: five stigmas, five styles and a five-celled ovary. In addition, they typically have 22 stamens, which are the male reproductive parts. Research has shown that good size and shape in apples and pears are correlated to the presence of 9-10 seeds per fruit. All five stigmas need to be pollinated to ensure that this number of seeds are formed.

Pollination vs Fertilization

Although they are distinctly separate processes, often the terms pollination and fertilization are used interchangeably.  Pollination is the process of pollen transfer to the stigma. Pollination requires a source of compatible pollen and a means of transfer (e.g. honey bees or spray application). This process must occur while the stigma is receptive. Fertilization is the process in which the pollen tube grows through the style, enters the ovule and releases its sperm cells which fertilizes the embryo and endosperm. Both are critical to fruit set.

Effective Pollination Period

For successful fruit set, it is important to consider the Effective Pollination Period (EPP) or the period in which pollination must occur in order to achieve fruit set  This varies with crop, cultivar and weather conditions. Typically in apples and pears EPP is approximately 2-5 days depending on variety and weather.

EPP = Length of time ovule is viable – time required for pollen tube to grow down style

For example in WA38, assuming ideal weather conditions, the stigma is receptive to pollen for up to 9 days. Ovules are also viable for about 9 days. After pollination, it takes approximately 7 days for the pollen tube to grow to the ovule and fertilize it. Using the formula above we arrive at an EPP of 2 days, meaning each flower has a window of 2 days to be pollinated after it opens. This period can be slightly different depending on variety and weather conditions, but 2 days is a good rule of thumb for apples and pears.

Timing is Critical to Pollinating High-Quality Fruit

In order to achieve full seed count each stigma would need to be pollinated in that two-day window. Furthermore, it’s important to note that apples require cross-pollination from a different compatible cultivar to set fruit, ensuring genetic diversity and fruit development. Given the 2 day EPP window this makes achieving ideal pollination a challenge. Both pollinating varieties would need to provide pollen in this window. If the King bloom are to be targeted, pollinizers should be selected accordingly. A pollinizer that blooms during the 2nd half of the commercial variety bloom may not provide enough pollen for ideal King bloom pollination. In this situation targeted pollen applications may help without creating crop load issues.