If you want to grow epic potatoes, there’s no one better to learn from than Jim Gerritsen, founder of Wood Prairie Family Farm in Bridgewater, Maine. Jim has over 45 years of experience growing organic potatoes and he came on the podcast to share everything you need to know to have a successful harvest, from preparing the potatoes and soil to preserving tubers so they last for months.
Jim is a third-generation farmer who started Wood Prairie Family Farm in northern Maine when he was 21, and in recent years has passed the torch to his son, Caleb. The farm is 115 acres and has been certified organic by the United States Department of Agriculture since 2002. It also has the Maine Seed Potato Certification Program seal of approval, meaning it can sell potatoes certified by the state to be free from disease and damage.
Maine was the nation’s leading potato-producing state about 70 years ago, and Aroostook County, where Wood Prairie Family Farm is located, was the center of the “potato empire,” according to Jim. Potatoes have been grown in the region since the arrival of the first European settlers, and today, Maine continues to be the national leader in growing seed potatoes.
This week’s preview of my conversation with Jim from 2021 is very timely, as potato planting time approaches. For a detailed walkthrough of everything we discussed, complete with photos, check out the original show notes.
While you’re here, I want to take a moment to remind you that I have a new book, “The Vegetable Gardening Book: Your complete guide to growing an edible organic garden from seed to harvest.” It’s packed with insider tips and new information to help you improve your gardening and overcome challenges.
Why Choose Organic Seed Potatoes
Conventionally produced seed potatoes were treated with systemic fungicides and insecticides and given synthetic fertilizer. But an organic seed potato hasn’t been treated with chemicals, and that means it’s a case of “survival of the fittest,” says Jim. Therefore, organic seed potatoes are hardy, with more vigor and better disease resistance. In fertile soil, organic seed potatoes will grow into healthy plants that don’t need chemical pesticides and fertilizers, and the tubers will be richer in nutrients.
For a healthy potato crop and perfect tubers like these, start with certified seed potatoes, which are free of pathogens and damage.
Why Maine is a great place to grow epic potatoes
Two things that make Maine a great place to grow potatoes, according to Jim: climate and soil. Maine benefits from being far north, where it’s not very hot in the summer, he says. It also has a good distribution of rainfall, cool nights and sunny, warm days. And the soil is sandy and well drained.
Potatoes are a cool season crop with shorter growing seasons to the south. But in northern Maine, potatoes can grow year-round and can be harvested in late September and October.
The difference between seed potatoes and new potatoes
To make seed potatoes, farmers kill the top growth of potato plants before the tubers have reached their maximum size. They are left in the ground for a few weeks so that the moisture content of the skin decreases. This hardens the tubers so they can withstand the rigors of mechanical harvesting and long-term storage.
The “new potatoes” were harvested while the plants still had green leaves, which were not killed, cut or removed. The tubers are immature and tender, with skin that can be rubbed with a thumb. Having access to real new potatoes is one of the benefits of growing potatoes at home.
In the Life Year of a Seed Potato Farmer
The growing cycle for seed potatoes in northern Maine begins in mid-April. It takes about a month to warm the tubers for planting, so that’s when Wood Prairie Family Farm puts out about 25,000 to 30,000 pounds of seed potatoes to germinate.
When the weather has dried out and the soil has a temperature of 50 degrees at 7 a.m. at a depth of 4 inches, conditions are suitable for planting. This is usually between May 15 and 18. It then takes a few weeks to plant everything, finishing in early June.
In August, the teams “kill” the fields. Organic farmers use propane torches to kill top plant growth, or they may use mechanical beaters; however, using beaters poses the risk of spreading mosaic virus.
The tubers, once harvested, need a dormant period of four to eight weeks before germinating and growing.
To encourage seed potatoes to sprout, they can be treated with gibberellic acid, which is derived from seaweed. But at Thanksgiving, tubers that have been stored will germinate easily without treatment.
Wood Prairie Family Farm works seven days in early March to keep up with shipping orders.
Jim’s instructions for planting seed potatoes
Gardeners can take the tubers out of cold storage a week or two before planting and warm them to encourage germination. Once they have germinated, the tubers must be placed under the light so that the sprouts remain compact.
An egg-sized tuber should be cut in half before planting. A smaller tuber should be left whole. A tuber larger than an egg should be cut into several sections, each weighing about 1.5 ounces.
In sandy soil, gardeners can cut seed potatoes and plant them immediately. But in clay soil, which retains water, Jim advises allowing the cuttings to callouse for three or four days before planting.
Another trick Jim recommends is soaking the exposed cut in agricultural lime to dry it out, making it less hospitable to pathogenic fungi. Plus, potatoes love the calcium in lime.
Seed pieces should be planted 2 to 4 inches deep. Anything deeper is likely to cause the tubers to rest in…
