When to plant Turnips in District of Columbia

In spring, Feb 20 – Mar 20 in Washington.

In fall, Sept 1 – Oct 15 in Washington.

USDA's earliest safe spring and latest safe fall planting dates, matched to each place's average frost dates.

Turnips planting dates by place in District of Columbia
PlaceSpringFall
WashingtonFeb 20 – Mar 20Sept 1 – Oct 15

Planting dates: USDA Home and Garden Bulletin No. 9 (1967), tables 4 and 5. Frost dates: NOAA U.S. Climate Normals 1991–2020. “—” means the place's frost date is outside the table. The full USDA table for turnips.