How Potatoes Grow
This article focuses on the growth of “white” potatoes – your standard every day potato which is a member of the Solanaceae family which includes tomatoes, eggplants and capsicums. Sweet potatoes are a different family than white potatoes. The sweet potato is a member of the morning-glory family, Convolvulaceae. Sweet potatoes (Ipomoea batatas) are not actually a tuber, but a storage root.
Knowing the growth stages for potatoes and other tubers will help you track your potato plant’s development and know when to check the plant’s “vital signs.”
Potatoes Have 5 Growth Stages
There are five stages for White potatoes, similar for other tubers like Jerusalem artichokes (sunchokes):
I Sprout development
II Vegetative growth
III Tuber initiation
IV Tuber bulking
Stage I: Sprout Development
In Growth Stage I, the eyes on the tuber piece that you’ll plant develop sprouts and push through the soil. These sprouts then develop roots at their base.
Stage II: Vegetative growth
Growth Stage II is the vegetative growth stage, when leaves and branch stems grow from nodes along the potato sprouts. Underneath the ground, roots and stolons develop. Photosynthesis begins—the process which will ultimately produce the excess starch that will be stored in your potatoes.
Growth stages I and II last between 30-70 days, depending on the environment and cultivar.
Stage III: Tuber Initiation
In Growth Stage III, new tubers form at the tips of the stolons. Tubers are not enlarging at this stage, which occurs at the same time as the start of flowering in many cultivars. It is especially critical at this stage that your potato plants receive a steady water supply.
Stage IV: Tuber bulking
Tubers begin enlarging in Growth Stage IV, the stage known as tuber bulking. During this stage, the potato plant accumulates water, nutrients, and carbohydrates. These are deposited in the tubers, usually 5-15 which grow to larger size. Tuber bulking can last up to three months.
Stage V: Maturation
In the maturation stage, the potato vines turn yellow, lose their leaves, and eventually die. Photosynthesis decreases and tuber growth slows. The dry matter contained in the tubers reach its maximum, and tuber skins “set,” or become less fragile (Skin set has not yet occurred in “new potatoes” that are preferred by so many gardeners, when potato skins are fragile, even papery.)
Our new book “How to Grow Perfect Potatoes” is currently in the final editing stage and will be released soon.