Knowledgebase
Sprouting Onions and Potatoes #894771
Asked March 18, 2025, 1:01 PM EDT
The client harvested his onions in the fall and stored them in his refrigerator. They have sprouted. Can he plant them this spring and expect a new crop? He also harvested his potatoes in the fall and stored them in his basement. They have sprouts 11 - 12 inches long. Can he plant them and expect a new crop/
Rockingham County New Hampshire
Expert Response
Hi Wayne,
Thank you for reaching out to UNH Extension Yard and Garden Infoline:
It appears to be unlikely that sprouted onions will produce a new crop of onions. Since onions are biennial, the sprouted onions will most likely form flowers and onions that flower develop mushy bulbs that are no longer edible.
General onion growing resources, not specific to the sprouting issue:
https://extension.unh.edu/blog/2020/03/it-better-grow-onions-seeds-sets-or-transplants
https://extension.unh.edu/blog/2020/10/how-do-i-get-my-onions-grow-bigger
https://extension.umn.edu/vegetables/growing-onions
https://nevegetable.org/crops/onion-scallion-and-shallot
Regarding the sprouted potatoes, you should be able to grow potatoes that have sprouted. We recommend cutting the potatoes so that each piece has only a single sprout, leave them in a dry place for a day or two so that the cuts have a chance to toughen over to prevent spoilage, and then plant them in growing media. It is still too cold to put them outside right now, but under lights should work until it warms up. Potatoes can handle light frosts, but not extended freezing temperatures.
Also, there is a method referred to as "Green sprouting" potatoes prior to planting.Some references which discuss green sprouting follow.
https://extension.umd.edu/resource/growing-potatoes-home-garden/
This article recommends keeping whole tubers in the dark at room temperature until
they sprout. Once they've sprouted, the tubers are exposed to light to keep the sprouts short. The potatoes would be cut into seed pieces (with at least one good sprout) and planted.
https://extension.umaine.edu/publications/2077e/
This article references "pipping” or “green sprouting” which can be used to encourage early production.
https://nevegetable.org/crops/potato
The New England vegetable Management Guide has quite a bit of information about potatoes including green sprouting.
I hope this information is helpful. Please feel free to reach out to us if you have additional questions.
(Written by Wendy Smith, Master Gardener Volunteer, posted by Sean O'Brien, UNH Extension Program Manager)
