Potato Tuber Physiological Age, Sprouting and Emergence

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

I recently received a question about variable potato sprouting in the field. While field and planting conditions, soil temperatures, seed piece handling all have an effect, another factor is seed age.

Potato tuber physiological age will determine seed piece sprouting. The physiological age is affected by harvest conditions, calendar (chronological) age, and storage conditions.

During seed tuber storage, the main influence on physiological aging is temperature. Higher storage temperatures cause greater physiological aging, colder storage keeps seed potatoes in a young stage.

In general seed potatoes can be divided into old and young physiological groups. Physiologically older aged seed emerges earlier, grows faster, yields higher early, and yields less later than physiologically young unaged seed. Physiologically young seed has more vigor, produces higher yields of larger tubers than old seed and is ideal under long production seasons.

To age seed, store at 38°F then before planting store for 2 to 6 weeks at 55-60°F. To hold young seed, store at 38°F and warm to 45°F just before cutting and plant in soil about the same temperature as the tubers.

Field Characteristics of Physiologically Young and Old Seed

Characteristic Young Seed

Old

Seed

Emergence slower faster
Stand greater lesser
Early Vigor greater lesser
Foliage more less
Stems/Plant less more
Tuber Formation later earlier
Formation Period longer more uniform
Tuber Number less more
Tuber Bulking longer shorter
Tuber Sizing larger smaller
Senescence later sooner
Early Harvest Yield lower greater
Late Harvest Yield greater lower

When large tubers are desired, young seed that produce few sprouts should be considered. For early fresh market, older seed may be more desirable to get a higher yield early and a quicker vine senescence. Older seed also may be more desirable where a smaller tuber is sought.

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