late spring frost
Refers to frost that occurs later than usual in spring, potentially damaging crops.
今年は遅霜で野菜がやられた。
This year the vegetables were damaged by a late spring frost.
晩霜 (ばんそう) is a synonym with the same meaning, but 遅霜 (おそじも) is more common.
Standard kanji spelling for 'late spring frost'.
Alternative kanji spelling; 晩 also means 'late'.
Compound of 遅 (late) + 霜 (frost). The reading おそじも is a straightforward combination of the kun'yomi readings.