If you plan to replant store-bought potatoes, you must let them sprout first, a process known as chitting. Potatoes that have sprouted have a much better chance of growing into healthy new plants than those that didn’t. But how long does it take store-bought potatoes to sprout?
The average time store-bought potatoes take to start sprouting is 30 to 140 days, depending on potato variety and environmental conditions. The ideal light, temperature, and moisture conditions are crucial, but it also depends on whether the suppliers sprayed the potatoes with a sprout inhibitor.
Interested in learning more about what makes potatoes sprout faster or slower? In this article, we’ll discuss in detail the factors that affect potato sprouting, how to time potato sprouting, and what to do with sprouted store-bought potatoes. Read on.
Why Potatoes Sprout
Sprouting is a natural part of the reproductive cycle of potatoes and the earliest step in creating a new potato plant.
All potato varieties have a dormant phase after harvest, where they will not sprout because they don’t want to be planted during winter. After this dormancy period, the potato tuber prepares to sprout with the help of the right environmental conditions.
Interestingly, potatoes don’t need to be in water or soil to sprout like other plants. They contain sufficient nutrients to begin growing a new plant while sitting on your kitchen counter.
When conditions are right, an enzyme in potatoes turns the starches into sugar or energy, which is then used to form sprouts. These sprouts grow or emerge from the eyes of the potato, and you will notice a tiny white indent that develops into a white and green sprout.
If you don’t plant the potato, the sprout will use up all the sugar in the tuber until it wrinkles, dries off, and dies.
If you do plant the sprouted potato, however, the sprout soon breaks through the soil surface and produces stems, leaves, and roots, effectively starting life over for the potato. The old tuber dies and, in its place, roots grow.
Timing Potato Sprouting Right
If you’d like to grow store-bought potatoes using the chitting process (allowing potatoes to sprout before planting them), knowing when your store-bought potatoes will start sprouting is critical.
This is because the best time to plant potatoes is in early spring, when temperatures range between 45 and 50 °F (7.2 to 10 °C). And since store-bought potatoes take 30-140 days to start sprouting, you need to plan so they can sprout properly before planting time.
Ideally, you should start chitting six weeks before planting to give the potatoes time to sprout well. Potatoes require several strong sprouts to do well after planting, giving you a quick harvest.
But even if you don’t want to plant the potatoes, it’s still good to know how long they take to sprout and go bad so you can cook them before then. Once potatoes start sprouting on your counter, they quickly become inedible because of withering.
If you would like to explore your options for storing your sprouted potatoes for planting, check out my article: 7 Ways To Store Sprouted Potatoes for Planting
Factors That Affect Potato Sprouting
The below factors affect potato sprouting:
Temperature
One of the best ways to keep store-bought potatoes from sprouting is storing them in a cold dark place, at around 38 °F (3.3 °C). This is why the space under the sink works so well as long as there is no moisture down there.
Therefore, if you want your potatoes to sprout fast, you should store them in a warm, bright place. While potatoes do not require light to sprout, keeping them away from the dark helps speed up the process. Do not expose them to sunlight, though, as this will lead to shorter, tougher sprouts that can easily break off.
Place the potatoes at 51-70 °F (10.6-21.1 °C) or in your house at room temperature if it’s not too cold. Be careful with temperatures over 65 °F (18.3 °C), as the potatoes will sprout too fast and deplete energy reserves, which will cause the tuber to shrivel up and die sooner than you’d like.
You should do this about two weeks before planting to encourage shooting. If the sprouts get too long before you are ready to plant, you can always take them back to a cold place for a while to slow down the process.
The sprouts should be 1 inch (2.5 cm) long during planting, and each tuber should have at least two healthy sprouts to increase the survival rate.
If the potato sprouts too soon, cut off any sprout longer than 2 inches (5.08 cm) to stop it from taking energy from the tuber. Letting a tuber get more sprouts is wise because you can cut it into two or more pieces thus have more seeds to plant.
If you decide to cut a potato into pieces, ensure each piece has at least two sprouts and allow the cut area two to four days to dry up so it won’t rot when planted.
Humidity
If you want potatoes to sprout fast, the next secret is to keep them in relatively moist conditions. Dryness works the same way as darkness in keeping the tuber in a dormancy state, and it also causes them to dry up and die.
According to the University of Maryland, 90% relative humidity at 40-50 °F (4.4-10 °C) is ideal if you want your store-bought potatoes to last longer in the kitchen.
If you increase air moisture and temperature, the potatoes will sprout faster. Do this by keeping the potatoes in the kitchen or bathroom where the air moisture is always high or putting the tubers inside a perforated plastic bag.
Alternatively, and we recommend this, lay the tubers on a bed of moist soil in a container placed somewhere indoors. You can moisten the soil periodically by spraying some water on it to mimic spring conditions.
Dormancy
As already mentioned, every potato variety has a resting period between harvest and sprouting. According to the University of Idaho Extension, this period ranges between 30 to 140 days.
Environmental conditions such as the temperature and humidity in the area where the tubers are stored can shorten the dormancy period a little bit, but the range remains the same. Therefore, it is prudent to determine the dormancy period of the potatoes you buy.
The best way to deal with this is to buy the potato variety mostly planted in your area. This will mean that people around you know more about it (how to take care of it and dormancy period), so you won’t have to guess.
Also, because that variety does well in your area, it will have a better chance of surviving and thriving than other varieties.
Organic Potatoes
Farmers are discouraged from using store-bought potatoes for planting because most of them are treated with a sprout inhibitor known as chlorpropham. The treatment prevents potatoes from sprouting during transit, storage, and when on display at the stores.
To avoid this issue, look for organic potatoes that haven’t been treated with chlorpropham. You can find them in organic stores or neighboring farms if you know people who farm potatoes organically or for their consumption.
The best thing, however, would be to buy seed potatoes meant for planting because they are safer and not treated with a sprout inhibitor. Most gardening stores sell them seasonally, so you can order from a reputable seed company.
Potato Placement
Lastly, you can encourage store-bought potatoes to sprout by storing them with fruits and onions. Ripening fruits like apples, bananas, and avocados emit ethylene gas, which helps set off the germination process.
Onions also produce a lot of ethylene gas which can either make the potatoes rot or sprout, depending on the environmental conditions.
What to Do With Sprouted Store-Bought Potatoes
Store-bought potatoes are often vulnerable to diseases such as potato blight and dry rot. Even if your potatoes survive and give you a harvest, the pathogen that causes the disease remains in the soil for months, even years, and can affect other plants as well.
In other words, you don’t want to risk exposing your organic garden to such adversity. To avoid this, plant the tubers in containers where you can throw away the soil after harvest and protect your garden.
You will need large containers for this, ideally 5-gallon buckets with 5-6 inches (12.7-15.24 cm) of moistened soil.
Plant the potatoes with the sprouts facing up and cover them with soil. You will want to keep the buckets in an open space where they can get enough sunlight and oxygen but away from frost.
You should also water the plants often to ensure the soil is moist. Initially, keep the watering to once a week until the tuber dies, and then you can increase it to thrice a week when the sprouts are big and above ground.
Wrapping Up
Chitting store-bought potatoes gives you at least a two-week head start when growing potatoes at home. It’s also the only way to ensure you plant only those tubers that will thrive if well-taken care of.
Just be sure to time correctly and have your sprouted potatoes planted before the last frost date. As for diseases, plenty of herbicides exist to protect your plants and give them the best chance of thriving.
