Growing plants may not be rocket science, but getting 65,000 plants ready for the Friends School Plant Sale is a bit like a NASA countdown at Glacial Ridge Growers. Mothers Day week is “Week Zero,” of course. We visited their greenhouses during Week +9, when Jeremiah Stark was just getting ready to seed some annual flowers. Out in the greenhouses, the results of earlier seeding work were in evidence—“benches” covered with plug trays, each filled with tiny seedlings.

As Week 9 leads to Week 8, then 7, and the weather warms, the plugs will be transplanted into the pots you see at the sale, and the plants will be moved to quonset houses to put down healthy roots.

Jeremiah’s father, Gene Stark, started the business as Greenfingers Farm in 1972 in Nebraska. With his wife, Muriel, Gene started a greenhouse as a way to get young plants for their organic vegetable business. At first it was a summer job— a break from his day job as an elementary school teacher. He liked it so well that he went full-time five years later, and he’s been at it ever since.

When the family moved back to Gene’s home town of Prior Lake, Minnesota, in 1982, they brought the business with them and a Twin Cities tradition was born. Muriel still teaches elementary school, while keeping the business side of things under control—ordering, scheduling, invoicing.

The family continue to sell organic produce at the Saint Paul Farmers Market during the summer until the covid pandemic. Gene has been committed to organics and natural greenhouse methods from the beginning (although most of what Glacial Ridge produces for the Plant Sale and retail nurseries is not certified organic—see more below ).

In 2003, facing increasing pressure from rapidly developing Prior Lake, the Starks closed their retail greenhouse and moved the business to Glenwood, Minnesota (south of Alexandria), and renamed it Glacial Ridge Growers. Out on the prairie, with pheasants and wild turkeys for company, they spend the year in a seasonally changing series of tasks that results in many of the great plants you find at the Plant Sale.

Growing Up in the Greenhouse

Jeremiah said he remembers always being in the greenhouses. Gene called Jeremiah their first “flat filling motor”—he would push the flats along as they were filled with soil. After earning degrees in landscape design and mechanics, Jeremiah returned to the family business. His four sisters, all at varying distances from Glenwood, are veterans of Greenfingers or Glacial Ridge as well.

Today, Jeremiah can still be found starting flats of plants (see photo below). He feeds a tray of 392 “plugs” onto the belt below a row of thin tubes. Turning on the vacuum, he watches as the tubes dip into a tray of seeds, each picking up one or more seeds with suction, and then dropping them into the plug tray. The tray moves down the belt exactly the length of a plug, as the machine proceeds to fill up the tray.

Once it’s full, the tray may be refrigerated for a few weeks to cold stratify the seed, or it may go right into the greenhouse to await germination.

Working with Nature

Although most of their plants are not certified organic, Glacial Ridge relies on natural methods and technical ingenuity to grow their plants without pesticides or herbicides and to minimize the ecological footprint of the business. Every inch of space is used in the greenhouses: There are no permanent aisles between the rows of plants—instead, the benches can be moved around easily to make an aisle when it’s needed, maximizing the space available.

Temperature is controlled by computers, so that the plants get what they need when they need it, which means the Starks don’t need to use growth retardant chemicals (a common practice in conventional greenhouses). They let the greenhouses freeze solid from November to January, which decreases the insect population, and then let ladybugs and other insect predators take care of any new aphids and thrifts that appear with the spring months. Airflow controls fungus and mildew.

“We try to take the good things from technology to help us do better, while leaving out the bad things from technology, like chemicals,” Gene said. “Computers help us to not use chemicals. We try to think about what makes environmental sense.”

Self-taught in the business of horticulture, Gene says that his favorite part of the work is the sheer diversity of tasks required and the need to always be learning something new.

Gene recalled how much things have changed since he got into the business. “We used to broadcast seed into open trays for germination. Then we had to transplant the small plants, and separate their tiny roots. You lost a lot of plants that way.” Now with the plug trays and mechanical systems for filling them, there is less waste. Many of the plugs are still transplanted by hand, but because each small rootball is self-contained, it’s manageable.

During the busy spring season, Glacial Ridge employs local farmers before settling back to the family work unit of Gene and Jeremiah in the greenhouse or fields, and Muriel on the business end. Summer is a break from spring (in the weeks after Week Zero), when they turn their attention to planting, tending and harvesting vegetables so they can bring them to market in Saint Paul. And Gene gets a chance to do some writing, including a recently completed novel [when this article was written in 2007].

The Weeks Go By

By the time you read this, it will be at least Week +5, and the plants will be growing big and strong at Glacial Ridge. The quonset houses will be full, with their vents opening and closing throughout the day to control temperatures. The automatic watering system will be doing its job, and the Starks will be thinking about their next round of tasks or planning something new—more coldframes to overwinter plants, more quonset houses.

Week Zero only comes once a year, but there’s always a new season around the corner at Glacial Ridge.


Young man peering at a piece of equipment with a light shining on it

Jeremiah watches the yellow seeds as they are picked up and dropped into the plug tray (left).

Native plants at Glacial Ridge

When Green Fingers Farm became Glacial Ridge Growers, it also committed to a new emphasis on native plants.

Gene believes in growing plants that are at home in our Minnesota environment and that provide habitat and food for native insects and birds.

“I looked back at some of the things I used to sell in the retail greenhouse that are now known to be invasive, like purple loosestrife or buckthorn,” said Gene. He realized that part of the way to make sure that doesn’t happen again is by selling plants that originated here.

Ornamental grasses are one example where nonnatives sometimes take over niches that belonged to native grasses. In response, Glacial Ridge has limited its list of grasses to native species.

How do you get native plants into the hands of gardeners? Gene says the plants have to be affordable, with good information available so people know what to do with them. To that end, Glacial Ridge provides an attractive, detailed tag with each plant.

Walking through the greenhouse, it’s easy to see why native plants have earned a reputation as harder to grow (resulting in higher prices than non-native seed-grown perennials, in many cases). Their seed germination rates vary greatly, even from year to year. That means their plug trays have empty spots, so more trays and more seed needs to be planted to get the desired number of plants. Many of them don’t like the cool greenhouse temperatures suited to the annuals and non-native perennials during spring, and so require more energy input.

Figuring out those variations is part of the challenge that keeps the Starks interested, though. There are lots of things to learn about propagating native plants.

Glacial Ridge is committed to native wild flowers and grasses, despite and because of the challenges. They have only to look outside the greenhouse to see the Minnesota prairie and feel inspired.

Some of Gene Stark’s favorite native plants

  • Cup plant (Silphium perfoliatum) and Compass Plant (Silphium laciniatum) for fences or boundaries
  • The lesser-used coneflowers like narrow-leafed (Echinacea angustifolia) and pale (E. pallida).
  • For wetter areas, swamp milkweed (Asclepias incarnata), blue vervain (Verbena hastata), great blue lobelia (Lobelia siphilitica) and the wild iris (Iris versicolor)
  • Ironweed (Vernonia fasciculata)
  • Prairie cord grass (Spartina pectinata), to replace and outcompete the invasive reed canary grass (Phalaris arundinacea)
  • Blazing stars, beyond the more common Liatrias spicata (which is not a Minnesota native )
  • Early sunflower (Heliopsis helianthoides) for its long bloom time
  • Wild petunia (Ruellia humilis)
  • Culver’s root (Veronicastrum virginicum)
  • The many under-appreciated varieties of goldenrod, but especially Rigid Goldenrod (Solidago rigida) and Zigzag Goldenrod (S. flexicaulis) for shade