It was a childhood observation that changed the life of Joel Karsten, and in turn revolutionized the way many people grow vegetables.
Mr. Karsten, 44, author of “Straw Bale Gardens” (Cool Springs Press, $19.99), started the straw bale gardening phenomenon. Since the book was published in March 2013, thousands of gardeners from just about every country in the world have tried his techniques, which he pioneered shortly after receiving a degree in horticulture from the University of Minnesota.
“Necessity is the mother of all invention,” he said in a phone interview. “I was broke because I was young, right out of college and I just bought a house.”
He said he couldn’t afford to buy compost to amend the thin layer of top soil covering “this awful construction fill” at his new house. He got the straw bale idea from the thistles he saw growing out of broken bales on the dairy farm in rural Minnesota where he grew up. As a horticulture graduate, he knew the nutrients that tomatoes and peppers require are similar to what thistles need. He began to experiment.
“I’ve been doing this for 21 years. For the first 14, nobody really cared a whole lot,” he said with a laugh.
Then he was discovered by a local television reporter. First, it was local garden clubs asking him to lecture. Soon it was gardeners from across the country. Now his book is translated into 12 languages and is one of the most popular garden titles in the world.
In my own garden, I gave straw bale gardening a try last year with mixed success. After talking to Mr. Karsten, I realized I did just about everything wrong.
The first step is to condition the bale(s) with water and a high-nitrogen fertilizer such as what’s used for lawns. Organic gardeners can use blood meal. High-nitrogen fertilizers work because that’s what bacteria really eat, he said.
The bale is soaked every day for 12 days with the diluted fertilizer mix.
“You’re building up bacteria inside the bale and those bacteria are going to colonize the inside of the bale,” Mr. Karsten said. “They are going eat the straw and turn it into soil.”
At the end of the 12 days, it isn’t straw anymore. It’s pretty much the beginning stages of soil or compost. The idea is to maintain a sterile environment for new plants.
“We have no weed seeds, no disease (and) no insects from last year’s garden,” he said. “As long as you never put a shovel of soil on top of that bale, you’ll never introduce those issues to your bale.”
The system works with one bale, or many. Mr. Kartsen likes to arrange five bales end to end. Whatever number you use, be sure to leave the strings on. He said compressed straw decomposes faster. He also recommends finding the heaviest, tightest bales available; they will usually last two seasons.
“It’s raised-bed gardening without the raised-bed price,” he said.
The first year he grows crops such as tomatoes, peppers, cabbage, cucumbers, greens and just about anything you could plant in a conventional garden sans sweet corn. The next year, he focuses on root crops and others that grow inside the bale.
Mr. Karsten grows in both the tops and sides of bales. To create a planting hole in the side, “take your rake handle and punch right between the two strings at a downward angle,” he said, adding that herbs work well in the sides of bales.
He has a few other tricks up his sleeve. With tomato plants, he’ll cover the top with a thin layer of sterile planting mix and plant a whole packet of basil seeds. As they sprout and start to form roots, he moves them to the sides of the bale. The same technique could be used for greens, too, especially later in the season as things cool off.
During the season, he highly recommends using a drip irrigation system hooked up to a timer to water the bales. They need 1-2 gallons of water a day when it gets hot and there’s no rain. The key is to keep the bale consistently moist.
Mr. Karsten said he never imagined he would be traveling the world, showing people how to garden. He also has a website, www.strawbalegardens.com.
“It is a dream come true for a little country boy.”
Doug Oster: firstname.lastname@example.org or 412-779-5861. Visit his garden blog at www.post-gazette.com/gardeningwithdoug. Twitter: @dougoster1.