Growing turnip in zone 5a

For spring plantings, direct sow 3 to 4 weeks before the last expected frost, typically late April in zone 5a. Most varieties reach harvest in 35 to 60 days: Hakurei finishes near the fast end at around 38 days, while Purple Top White Globe runs closer to 55 days. Spring plantings need to be in the ground early enough that roots mature before daytime temperatures climb consistently above 75°F, which tends to happen by late June in this zone. Roots that size up in summer heat turn pithy and lose the mild sweetness that makes the crop worth growing.

Fall plantings are more straightforward. Count back 6 to 8 weeks from the first expected hard frost, which in zone 5a typically falls in mid-October, putting fall sowing in late August to early September. Roots harvested after a few light frosts often taste noticeably sweeter than those pulled in warm conditions.

The primary disease concern for zone 5a turnip growers is clubroot, a soilborne pathogen that infects brassica roots and causes misshapen, swollen growth. Clubroot persists in soil for up to 20 years, so rotating brassicas to a different bed for at least 3 years between plantings is the main line of defense. Raising soil pH to 7.0 or above with lime reduces infection risk but does not eliminate it once the pathogen is established.

Late spring frosts are a listed zone challenge, but turnips tolerate light frost well, and young seedlings can handle temperatures into the upper 20s°F without significant damage. The greater timing risk runs the other direction: planting too late and having roots mature in summer heat rather than cool spring conditions. Fall crops largely sidestep this problem. Because the zone's autumn cools steadily from September onward, fall turnips rarely face the quality issues that affect spring plantings that drag into warm weather.