Aug 1, 2025

DeGrandchamp Farms’ high tunnel success

DeGrandchamp Farms, a Michigan blueberry and cranberry grower, is successfully growing some of its blueberries in high tunnels.

Entering its seventh season of trials, the South Haven grower has been producing greenhouse blueberries in 10-gallon containers in two 30-by-100-foot greenhouses. The protected structures produce more and earlier fruit than field-grown and flower a month earlier than the typical field mid-May bloom. The controlled environment produces blueberries 1.5 to 2 weeks earlier than field-grown, said Adam Shinske, farm manager.

“The greenhouses extend and create a longer growing season,” he said. “We’ve done a ton of different things to them, but you can definitely fully control the environment in there. If there was an event that knocked everybody else out in the Great Lakes and this was actually being done on a commercial basis, I think you’d have all your fruit.”

DeGrandchamp’s greenhouses produce 6,800 plants an acre compared to the farm’s typical 1,452 plants an acre field grown in three-foot spacings.

Circulating fans help with air movement via 1,500-watt electric garage-type heaters. Half stand heaters circulate air. The garage heaters are connected to electronic thermostats for temperature management, which helps l prevent frost damage during bloom or other cold winter damage.

The automated electric heaters represent an improvement over kerosene heaters, which worked well with the half fans but required manual refueling at 2 a.m.

If DeGrandchamp takes production to a more commercial level, plant spacing will become more important, Shinske said. He may consider pulling a mini harvester through the rows, though the spacing is likely a little tighter than Shinske would prefer. If he grew high tunnel blueberries on a larger scale, spacing would be an important consideration to prevent workers and equipment bumping against bushes.

“Those are some of the exciting things about it,” Shinske said. “High tunnel production isn’t really getting done here. Obviously, they’re doing container production in other parts of the country and world, but how are we going to do it here? There’s a massive amount of plants in that acre compared to a field acre.”

Tale of two greenhouses

Two greenhouses allow DeGrandchamp Farms to experiment with different practices.

Both houses use inflation fans during the winter months to provide insulation and protect against winter damage. In one greenhouse, two layers of polyethylene and an opaque layer decrease warming. In the other, it’s one layer of polyethylene and an opaque layer. In the spring when it’s time to start pushing the plants, the opaque is removed, leaving one house with a single layer of polyethylene and the other house with two layers. This enabled DeGrandchamp Farms to keep an inflation fan on one of the houses.

A nontransparent poly layer on top of a clear sheet helps decrease warming, which maintains plant dormancy. The two tunnels had the same insulation over the winter, but in the spring, Shinske pulled the opaque when he wanted to start pushing the plants. A data logger recorded temperatures. The results showed single, clear plastic sheets would work, while extra insulation in one house allowed fruit to mature a day or two earlier.

The trials have produced mixed results, mainly involving heat. As strong pollination is key to producing favorable seeds and seed counts — the less a blueberry gets pollinated, the smaller the fruit sizing.

Because manually removing the plastic sides on the greenhouses is labor-intensive and costly, plans are underway to install automated, custom roll-up sides this spring.. This technology is especially important in Michigan, where blueberry plants need protection during bloom and well into the spring. Roll-up sides are a smart solution solution, since blueberry bushes must be protected from intense heat, Shinske said.

Pollen degradation starts as temperatures reach 90° F and intensifies as the temps move up. In some years, greenhouse temperatures reached as high as 105° F. Exhaust fans aren’t adequate in lowering temperatures. At those extreme temperatures, plants go into self-preservation mode and stop photosynthesis, which not only affects pollen but also fruit sizing as the berries go through cell division. After pollination, berries begin sizing first through cell division, followed by cell expansion. Typically, due to the lack of frost threat, DeGrandchamp has been able to remove the plastic by the time the berries are in the cell expansion stage.

During the first year, the tunnels produced monster-sized fruit.

“It was crazy how big the fruit was,” Shinske said. “It was gorgeous fruit. It was really exciting, but it was just because we got the right weather and it didn’t hurt me with the inability to pull that plastic. I’ve had good yields in there — not every year, but to me, it’s all revolving around the heat and getting these roll-up sides installed that can roll all the way up to the peak with automation.”

Because MBG Marketing/Michigan Blueberry Growers Association focuses on member estimates, yield estimation is important.

“If you have everything growing in the exact same substrate and you’re doing the same thing to every plant, you’re going to have a much more uniform crop and better ability to estimate your yield,” he said. “It’s almost a fully controllable situation, which gives you a lot of peace of mind in the fact that you’re going to get that fruit and you’re not going to have a disaster and lose your farm.The more years we’ve been into it, the better it gets.”

The idea to grow blueberries in tunnels hit Shinske after attending numerous Michigan State University industry meetings. Often, when Extension personnel discuss high tunnels, growers decline to participate, mainly due to cost. However, with two vacant greenhouses in DeGrandchamp Farms’ diversified operation, which includes a floral nursery, Shinske saw an opportunity to experiment.

Doug Ohlemeier, Assistant Editor