Who doesn’t love potatoes?! They are versatile, store well, delicious and easy to grow. Let’s talk about the first steps to grow a healthy, abundant crop of potatoes.
The best place to start is with high quality seed potatoes. Can you use potatoes from the grocery store? Potentially, but there are a few reasons to spend a extra few bucks on proper seed potatoes. Cooking potatoes have most likely been treated with a chemical that inhibits sprouting, a natural tendency that is undesirable in the kitchen but necessary for cultivation. Organic potatoes may not have received this treatment, so would be a better choice than non-organic potatoes. And potatoes saved from the previous year’s garden are also an option, though there is the risk that they may be harboring bacteria that can negatively affect this season’s crop like Streptomyces spp. and Spongospora subterranea f. sp. subterranea, which are responsible for potato scab (Hudelson, 2005).
Seed potatoes are produced by experienced growers and should come with a guarantee that they are disease-free, physiologically young, and have been stored under appropriate conditions to ensure strong healthy growth once planted. Store your seed potatoes in a cool (3-4 degrees Celsius), dark place away from drafts, which may have a drying effect, until planting time arrives. Keeping the potatoes under these conditions encourages them to remain in a dormant state which will prevent premature sprouting. The ideal soil temperature for planting is 6 degrees Celsius or above. The earliest time to begin preparation for planting is a few weeks prior to this, around mid-April here in Medicine Hat, Alberta (zone 4b).
Why is preparation necessary and what does it entail? I’m so glad you asked! As mentioned above, seed potatoes are kept in a dormant state until planting time arrives, at which point they wake up and get growing. Prior to planting, seed potatoes should be suberized (if they are being cut) and chitted, two potato-related terms that I must admit were confused in my head for a time. When I mentioned suberizing to my partner he asked if this was the process of turning something into a Subaru (he’s clearly more of a car guy than a garden guy).
So, what does it actually mean? If your potatoes are heavier than 85 grams they should be cut to maximize the yield into pieces 45-65 grams each containing at least 2-3 eyes (Delaynoy). Cutting the potatoes, however, creates an opportunity for bacteria and fungus to infect the pieces which can lead to rot and a failed crop. The solution is suberization, a biological process whereby the seed potato heals the wounds you’ve inflicted during cutting by depositing suberin on the walls of plant cells, effectively creating a callus to protect the potato once it is planted in the soil. Simply allow the potato pieces to sit with the cut side up for a couple of days in a darker area until the wound has dried.
Once the seed potatoes are suberized, or if they were small enough to be planted whole, they can be chitted which involves encouraging the eyes, which are technically buds, to begin sprouting. This is accomplished by exposing them to indirect light and slightly warmer temperatures, gently warming them to 7-10 degrees Celsius. Once the spouts are about 2.5 cm long your seed potatoes are on their way to being planted. If there are many eyes that have sprouted, you might consider removing all but 3 of the healthiest sprouts as there is a limited amount of stored energy available in the potato piece to support the initial growth of the plant before leaves emerge and begin to photosynthesize. Now your seed potatoes are ready to plant, sprout side up, in your garden/container/grow bag/burlap sack/etc. A potato planting post with more information about best practices for planting potatoes is coming soon.
Tahoe Basin Master Gardeners. Spring Planting of Onions and Potatoes. University of California Agriculture and Natural Resources. Retrieved from https://ucanr.edu/sites/mglaketahoe/files/285860.pdf
Delaynoy et al.. Seed Selection, Storage and Cutting. Government of Manitoba. Retrieved from https://www.gov.mb.ca/agriculture/crops/crop-management/pubs/seed-selection-storage-and-cutting.pdf
Hudelson, Brian. (2005, April 24). Potato Scab. University of Wisconsin Horticulture. Retrieved from https://hort.extension.wisc.edu/articles/potato-scab/