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Culturing Greenhouse Potatoes
Click here to download a PDF of this article.
These potatoes will be shipped to you sometime in early March.
Green-sprouting. Begin your hoop-house potato cultivation by green-sprouting the seed. The basic concept of this practice is to encourage the seed piece germination in a protected environment. Market farmers can easily convert their walk-in coolers to green-sprouting rooms, and while smaller growers consider the window sill of their bedroom, as this process requires no irrigation. Spuds should be spread out in crates or on racks, no more than two layers tall, during the initial week-long period of 70-75 degrees Fahrenheit required to break dormancy. After a week, the spuds have germinated, and temperature may be reduced to 45-55 degrees Fahrenheit, and natural or artificial light should be added into the sprouting environment. Heated seedling houses or walk-in coolers can host this three or four week “greening period” as the sprouts begin to develop. Click here for MOFGA's detailed article on green-sprouting:
Hardening-off your seed. Once nightly temperatures are reliably above 20 degrees or so, you can harden-off the sprouted seeds in your unheated greenhouse. Expect to move your sprouted spuds outside at the end of March or early April, definitely after maple sugaring season. Cover your stacks of hardening-off seeds with a few layers of row cover to ease the transition, but make sure the plants still have access to light, crucial for their development.
Bed Preparation. Prepare the beds as you would any early, indoor crop, and dig furrows at least 18 inches apart. In-furrow fertilization is crucial for the successful production of any greenhouse crop, especially heavy feeders like potatoes. Here is a planting mix we like:
Planting. Plant into your furrows, spacing at 6 inches for baby potatoes, and 9 inches for a little bit larger new potatoes. Click here for Washington State University's studies on spacing and yield for baby and new potatoes. Cover the seed with soil and up to two layers of Agribon-19 for extra heat retention in the soil.
Caring for the crop. Irrigate with drip tape two or three days a week for a few hours, as needed. For best results, either fertigate or foliar feed with fish and kelp. Early season crops tend to wake up pests who like warm weather and tender foliage. We recommend preventative control of Colorado Potato Beetle with Neem Cake directly in-furrow during planting to repel and irritate eggs, larvae, or adult beetles. If you skip this step and run into pest problems, use OMRI approved Entrust as a foliar application.
Harvest. Pick in early to late June, depending on the variety. Usually while your squash and melons are just a few inches tall, you will have marketable potatoes and a market hungry for substantial vegetables.
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