noun
new potatoes
Refers to early-harvested, small, tender potatoes with thin skin, typically available in spring and early summer.
春になると、八百屋に新じゃがが並び始める。
When spring comes, new potatoes start appearing at the greengrocer's.
新じゃがは皮ごと煮るとおいしい。
New potatoes are delicious when boiled with the skin on.
じゃがいも is the general term for potato, while 新じゃが specifically refers to early-harvested new potatoes.
Compound of 新 (しん, 'new') and じゃが, a clipping of じゃがいも (potato).