Answer: They are treated similarly to turnips and other root crops. They do best in cool weather, but take about 100 days to mature, quite a bit longer than other root crops. Sow seeds as soon as possible after your last frost. However, they can stay in the ground right up until the ground freezes, so you could sow a second crop later in the season. (Count back from your first frost date to determine a planting date. The longer they stay in the ground, the sweeter they become.
There are two important things for growing root crops. The first is having a rich, loose, well-drained soil. Add several inches of compost 2-3 months before planting. Make sure the soil is loose and deep enough so roots have plenty of room to grow. You might want to consider raised beds for your root crops if you don't have well-drained soil. Add a phosphorus source to the soil before planting.
Add a balanced fertilizer (such as 10-10-10) when the plants are about 6 inches tall and the bulbs are starting to swell. Water well before and after applying fertilizer.
Spacing is another important aspect for root crops. Sometimes it's hard for gardeners to thin plants, but you may need to pull out seedlings as they grow. They should have about 4 inches of space between each rutabaga.
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