Rutabagas are a hardy vegetable that grow best in cool weather.
Rutabagas are sensitive to heat, and only grow well when
temperatures are 75°F and cooler. For most areas they should be
planted in the fall only. Plant seeds 14 weeks before the frost.
If you live in a mild climate with a late or no fall frost date
(after Nov 1), you might be able to grow turnips all during the
winter. Soil and Fertilizer Rutabagas grow best in a rich soil
and are susceptible to boron deficiency; amend with lots of
compost and fertilizer (chemical or organic) at planting.
Fertilizer: 16-16-8 at planting, Borax at planting. Harvest when
tops are 6-8″ tall and roots are 4-5″ in diameter. Similar to:
Turnips - Rutabaga Reference Sheet (Utah Extension Service)