Kirshbaum employs science, art for raising strawberries
A love for strawberries and a hobby of raising them led to a successful business for Stan Kirshbaum, who shared his knowledge of growing berries with the Dodge County Master Gardeners.
He began his business in 1980 with one-third of an acre, and the business has grown to 15 acres over the years.
About half of his business is U-pick. He hires workers (44 of them this year) to pick the remainder of the berries, and any that are not sold are taken to the nearby Edwin Brix Vinyard, Dodge County’s only licensed winery, where they are made into strawberry wine.
Kirschbaum is a past state president of the Wisconsin Strawberry Growers Association. With a degree in biology and a chemistry minor from UW-Oshkosh, he has combined science with the art of raising healthy plants.
He told the gardeners that the strawberry patches are on a three- or four-year rotation. Each year, he establishes berries on 5 new acres in the spring, and at the end of the picking season, he decides which of the existing patches was the least productive. Those are turned over and planted to an alternative crop.
Kirschbaum also emphasized the importance of an irrigation system in the strawberry business.
“It’s partly for water in the dry months, but mostly, it’s for frost protection,” he said.
“This year, especially, it was important because we had a hard frost in early May when the berries were blossoming.”
When temperatures drop to 32 degrees, he turns the water on, delivering about 50 gallons per acre per minute.The water sprays over top.
“As long as we can keep plants wet, we can save the blossoms," Kirschbaum said. "When water freezes, it gives off a little heat, and that’s what saves the plants.”
Other gardeners on the tour said they used blankets or row cover to protect the fragile blossoms on cold nights. Kirschbaum said he did that when he was just a hobby farm, but irrigation is the only way to save the blossoms on bigger acreage.
Explaining the history of strawberry growing, Kirschbaum said it dates back to Europe when the wealthy people showed off their gardens that included strawberries. When they came to the U.S., they brought plants with them; but he said they didn’t always turn out because some varieties of strawberries have male and female plants, and if the immigrants didn’t bring some of each, they were not successful in establishing a crop.
“There are no GMO varieties," he noted, "but we do have strawberries that have been crossbred to develop new varieties.”
He raises Honeyeye, Annapolis and Jewel and usually experiments with a new variety each year as well. Kavanash is another popular variety, but it does not do well on his clay-type soil as it requires a sandy soil.
Kirschbaum advised planting different varieties when establishing a patch so they won’t all be ready at the same time and it then stretches the season.
“Strawberries need well-drained soil and about an inch of water a week to do well,” he noted. “They need to dry out, though, between watering.”
When he does apply water, he does it in the morning so the sun will dry the leaves. If leaves are wet overnight, they will be more likely to develop fungus problems.
They also need to be weed-free. To accomplish that, Kirschbaum makes sure he starts out with clean fields. Quack grass, Canadian thistle, yellow nutsledge, fox tail and dandelion are common problems.
He buys clean wheat straw that he knows comes from weed-free fields, and the straw prevents dirt from splashing onto the leaves of the plants as wet dirt leads to fungus problems.
The straw, put on early, will keep the plants warmer. It keeps the blossoms, formed already in fall, from freezing.
A layer of snow over the crop is also a good insulator.
As plants age, the crown keeps getting longer and new roots develop off of it. Kirschbaum makes sure there will be dirt over top of the growing crown. He showed the gardening visitors the specialized equipment he uses to accomplish that task.
As runners develop, he and his employees walk through the fields, placing the runners in the row of growth.
“The majority of the production comes from the outside 6 inches of the plants where the sun hits the most," he said. "That’s why we have 12-inch rows spaced 40 inches apart.”
When Kirschbaum establishes the field, he places plants 15 inches apart in the row. As they develop, the runners fill in the space. When plants are missing in an area, he will fill the spaces with new plants.
Some growers have 36-inch rows, Kirschbaum said, but he likes space between for straw and room for pickers to kneel down between rows.
Strawberries like a soil with a pH of about 6.5 and less than 7. If it is too high, he adds some ammonium sulfate to lower it.
Kirschbaum also does soil testing, fertilizing accordingly. Generally, he adds 30 pounds of nitrogen at planting time and another 30 pounds in November. At times, the soil tests call for the addition of a little boron.
His farm is not organic, but he practices integrated pest management, only using chemicals to treat specific problems in certain areas. He said that’s different than in the past when growers had a set time to apply chemicals. Now they monitor fields closely and only use them when needed.
He uses an early herbicide that prevents the germination of weed seeds before planting the berries, and after planting, weeds are removed by hand or by cultivating.
Kirschbaum has some problems with predators, mainly raccoons. Deer also do a little damage. Birds like to steal berries in the spring, but he said, “We have plenty of berries to share with the birds.”