Blueberries and Bumblebees
The other day, my girls and I visited our friend Stephen Spear at his pick your-own blueberry farm in Dennis. He walked us out to the woods alongside the fields, where a box of bumblebees had just arrived from Michigan.
“There’s about 250 [bees] in there. So you see this little plastic door I have to look in there…There we go, there’s one coming out, and two, I’m gonna back up,” said Stephen.
The bees start flying out of the box, looking around and getting their bearings.
Stephen explains that the orange stuff on the bees is pollen.
Slowly, we follow the bees out of the woods and towards the blueberries. Stephen says he’s been bringing in mail order bumblebees to pollinate his crop for over a decade.
“They’re the common species for the Eastern part of the United States, bombus impatience is their Latin name and they’re basically the same as what we have around here naturally.”
When Stephen first started farming blueberries, local bumblebees pollinated the plants. But eventually, this stopped working.
“Because as the plants got bigger and there were more and more flowers, I had a year where I could see there wasn’t complete pollination.”
He could tell because the fruit was very small and has no seed in it. It was also kind of flat tasting, so when he saw that he knew he needed to supplement. There were just too many flowers in one place at one time for the locals to do the job.
Each blueberry flower has about twenty ovules, which are the female part of the plant that needs to be fertilized to develop into seeds. Unlike some fruits, which only need half or two thirds of their ovules pollinated, blueberries need almost all of them of them for good fruit development.
“But the thing about bumblebees is they can take care of all those in about three visits, whereas honeybees it takes them up to 20 visits to do the same thing. Bumblebees kind of co-evolved with blueberries and some of the other native flowers so their tongues are longer so they can get down that long umbrella shaped flower and they also have this technique that only a few other bees have and it’s called buzz pollination.”
According to Stephen, buzz pollination is when the bee clings to the open end of the flower and beat its wings a little bit—not so much to fly—but they just keep moving their wing muscles and it sets up a kind of a vibration where the pollen is dislodged and comes down the flower and gets all over them, which is what they want. In the process it gets on the female parts and begins to have fertilization.
When Stephen says female parts he’s talking about the ovules. And he says it would take 15,000 honeybees to pollinate his acre and a half of blueberries.
“And that’s so many you’d see them very easily in this case there’s three or 400 bees between those we brought in and the locals and you say gosh will it get fertilized and it does.”