This year’s growing season is not exactly off to an early start.
But a local gardener has a suggestion: Plant your vegetables in a bale of straw instead of in the ground.
It’s a humble method with old, rural roots, one that Joel Karsten of Roseville has been advocating for more than a decade. He started experimenting with growing vegetables in decomposing straw, inspired by his childhood memories of tall, healthy thistles sprouting out of wet bales on the farm. Encouraged by his results, he started teaching community education classes throughout Minnesota and Wisconsin, picking up almost 25,000 Facebook “likes” along the way. Now he’s published a book, “Straw Bale Gardens” (Cool Springs Press, $19.99), which was featured last month in the New York Times.
What’s so great about growing produce in old, rotting straw bales? Earlier vegetables, for one thing, according to Karsten. That’s enticing to cold-climate veggie gardeners, especially this year, when gardens remained buried under snow more than a month after the official start of spring.
So how exactly does straw-bale gardening deliver early vegetables?
“When you put tomatoes in cold soil, they just sit there until the soil gets to the right temperature,” Karsten said. But with a bale, “you create a really nice growing environment, similar to an expensive greenhouse.” Once you “condition” your straw (which means starting the process of decomposition), the interior of the bale heats up. By late May, its temperature could be 85 to 90 degrees, vs. 55 degrees for soil in the ground, he said, leading to rapid root production.
Tomatoes and cucumbers, in particular, prefer warm roots and cool tops, according to Karsten, but it’s very difficult to get that combination in the ground. In fact, planting veggies in a warm bale, rather than the chilly ground, reduces days to maturity by 10 percent, he said.
Karsten has tested it many times, he said. “It’s really fun to do a comparison, put a pepper plant in a straw bale and one in the soil,” he said. “A month later, the one in the bale is 20 inches taller than the one in the ground.”
John Ullmann of St. Louis Park is a bale believer. He took one of Karsten’s classes several years ago, and has grown veggies in bales the past two growing seasons, with plans to do it again this year.
“This is really my only way to have a vegetable plot,” said Ullman, who lives on a heavily shaded lot on Minnehaha Creek. He sets his 10 bales right in his driveway, the sunniest spot on his property. “You can put the bales anywhere, right on the asphalt.”
Gardening without a garden
That’s another benefit of straw-bale gardening, according to Karsten: You don’t have to have good soil — or even soil at all — because you’re basically creating your own, inside the bale as it breaks down. But you do have to give the bale a little help.
“People e-mail me saying they tried it and it didn’t work, the tomatoes died,” Karsten said. “I ask what they used as a conditioning process, and they say, ‘What is conditioning?’ If you don’t condition, you’re guaranteed to fail.”
Conditioning isn’t complicated, he said. “You’re basically adding fertilizer and water, for 12 days, to get the bale ready to go.”
Another mistake to avoid: Don’t use hay for your straw-bale garden. (Yes, city slickers, there is a difference.)
Hay and straw are often confused by those who didn’t grow up on a farm, but they refer to different plants entirely. Hay is usually baled grass or alfalfa, green in color, and used as food for livestock. Straw is yellow or golden, a byproduct of what’s left after small-grain crops are harvested and cut near the ground, with seeds separated from the stems. Straw has little nutritional value, but makes a good bedding material for livestock.
Because hay, unlike straw, contains seed heads, it’s not recommended for straw-bale gardening, because the hay seeds will compete with your crops.
If you don’t have access to a farm with straw, you can find bales for sale at www.strawbalemarket.com, a website Karsten started to help gardeners and farmers connect.
Bales are also sold at many garden centers, although you’ll pay a bit more, assuming you can find them. “I can’t keep straw in stock,” said Paige Pelini, co-owner of Mother Earth Gardens in Minneapolis. “People are intrigued” by the straw-bale method, she said, which appeals to customers whose only sunny spot is in a driveway or a place where they don’t want to dig up the lawn and plant a garden. Pellini hasn’t tried it herself, “but it makes sense,” she said.
How much straw do you need? About 15 bales will provide the same production as a 20-by-20-foot traditional soil garden, according to Karsten. “A good rule of thumb is five bales per person you want to feed,” he said. “It’s not enough if you’re big into canning, but if you’re just looking to eat out of it all growing season, that’s plenty.”
One and done
Bales are used for only a single growing season, since they’ve usually broken down and shrunk by the time fall arrives. But rotting straw is still useful to you as a gardener, Karsten said. “At the end of the season, pile it in the corner in a separate compost pile, and finish composting it over the winter. Turn the pile with a pitchfork, and add nitrogen. The following spring, you have a pile of the most beautiful compost you’ve ever seen. You’ve created your own high-quality potting mix, weed-free and well-drained. It has all the same great character you pay $12 for at the garden center.”
Straw-bale gardening has its virtues, but it’s not perfect. If your goal is an edible landscape that’s as pretty as it is productive, there’s no getting around that a bunch of shaggy straw bales are not likely to win you a spot on the neighborhood garden tour.
“They weren’t beautiful, especially toward the end,” admitted Michele Manion, who tried straw-bale gardening in her Bloomington back yard a couple of years ago. Her neighbors were “curious but not critical,” she said. “We tried to keep them as neat and organized as we could, and we planted ground cover on the bales” to camouflage the straw.
People, especially in urban neighborhoods, sometimes worry that their neighbors won’t like the looks of the bales, said Karsten, who recommends planting colorful annuals, such as petunias, impatiens or marigolds, into the sides of the bales. “ Herbs look nice, too,” he said.
Ullmann uses impatiens to beautify his bales. The notoriously thirsty plant also serves as a moisture gauge, he noted. When the flowers start to wilt, it’s time for him to water. His neighbors haven’t said anything negative about the bales in his driveway, he said, although, “I’m sure people look and think it’s the dumbest thing they’ve ever seen.”
Straw-bale gardening also isn’t ideal for all vegetable crops. Manion had great success with tomatoes and cucumbers, less with peas and carrots, she said. She’s planning to grow in bales again this year, but will concentrate on crops that performed well for her, while planting others in the ground.
Perennial vegetables don’t grow well in straw because they tend to break down as the bales break down, Ullmann said. “Asparagus is a waste of time.”
But for most vegetables, straw-bale gardening is the best method he’s tried, he said. “I used to grow vegetables in pots, but I can grow a lot more in a straw bale. We like it a lot.”