Spring is getting off to a late start here in Vermont, and in many other parts of the country as well. As a result our customers have been asking us what they should do with their potatoes while they wait for the snow to melt and the ground to thaw. One method you can try is called greensprouting, or “chitting” potatoes, which takes advantage of the extra time available to transform your potatoes from starchy spuds into verdant transplants.
Getting potatoes into and out of the ground quickly in the spring is really important. Cool, wet soil can lead to rot, and the longer the potato spends in the ground “waking up”, the more susceptible it is to attack by fungal diseases. One of the keys to successful organic farming is getting plants off to a healthy start when they are transplanted into the field. Transplant shock, or the adjustment to being outdoors in the big wide world, can set back schedules as well as yields, both of which affect a farm’s bottom line. The hardening-off process, of getting transplants ready to make the leap, is something people do regularly, so why put your potatoes into the ground without the same care?
I have been greensprouting or “chitting” my potatoes for years, and while it’s a little extra work, the results are totally worth it. The potatoes are ready to harvest about two weeks earlier and tolerate cool, wet spring soils much better. Plus, they can be planted later, and the time they spend sprouting inside is time they aren’t vulnerable to pests, diseases, and cold temperatures in the field. Rather than dropping seed potatoes in the row, as is traditionally done, I am really transplanting my potatoes as if they were seedlings.
Step One: Break Dormancy
The process is simple. The first step is to break the dormancy of the potatoes by keeping them warm and dark. I arrange them a few layers deep in a black crate and put them in a room that I keep at 70-75 degrees F. You could also place them on top of a seedling heat mat, on top of the fridge, or any other warm (not hot!) surface. The elevated temperature breaks the dormancy of the potatoes, and encourages them to produce multiple eyes. How long this takes can vary; some potatoes may have been stored better than others and will be slower to sprout, however you should ideally start seeing white shoots appearing in a week or two.
Step Two: Grow Out
Once the sprouts have emerged to about ¼”, the temperature should be lowered to 50-60 degrees F, and the potatoes should be exposed to natural or artificial light. I just use shop lights that I put right on top of the crates. This is the step that slows the growth of the sprouts, and allows them to undergo the really beautiful part of this process. The sprouts turn greenish purple, and the strength of the sprout attachment increases, making them less likely to get broken off during planting. However, even if the sprouts do break off, research shows that greensprouted potatoes still send up new shoots much more quickly than unsprouted potatoes. The greensprouting process also encourages seed potatoes to develop more shoots, resulting in plants that produce more tubers.
Step Three: Transplant
If you wait long enough, the sprouting potato forms true leaves. That’s the part that I really get excited about. I plant my potatoes by hand, and orient the seed potatoes with their new shoots and leaves up. If the seed pieces are of a larger size, I cut them just before they go in the ground. I try to have at least three nice eyes per piece, and I plan my cut so the cut side is as small as possible, thereby minimizing the risk of rot from the injury. Lots of people cut their seed potatoes a day or two before they plant, and allow the cuts to heal a little bit. We plant enough that we don’t really have the room to accommodate this extra step, and I find if you let the soil get warm enough, the risk of decay is fairly low. If the potatoes just have sprouts and no leaves, plant them so they are just barely covered, and they will send up shoots very quickly. If they do have leaves, plant so that just the leaves are sticking out of the soil. Most growers find that they shave 10-14 days off of the potato growing season by greensprouting, and are able to plant longer-season varieties than they would normally be able to grow successfully.
Potatoes are one of my favorite vegetables. Just think — when you dig them, you are the first person ever to have held this amazing food, and that same tuber holds life for the next season’s crop. The greensprouted tubers are a sight to behold in the early days of spring, and the lush mature plants are likewise beautiful. When they are all in bloom, with their rows of different colored flowers, you couldn’t find a prettier place on earth.