Turnips are a popular and delicious vegetable that prefer cool weather. In the Deep South, turnips are grown during the fall, winter and spring, while in more northern locations, they are started early before the last frost for a summer harvest. A second planting occurs later in the summer for a fall/winter harvest
The edible portions of the turnip include the greens and the bulbous underground stem, typically referred to as the root. Propagation by means of plant division is not optimal with turnips, and they do not respond well to transplanting. Therefore, the normal propagation method for turnips is to grow them from seed. Seeds should be planted thickly, and covered with ¼ inch of soil. Planting in rows 24 to 30 inches apart is ideal.
As noted above, seeds can be sown prior to the last frost in early spring in the north, but are more commonly saved for a late summer planting. Late July or early August planting helps them avoid turnip root maggot damage, as well. Leaving mature turnips in the ground until you are ready to eat them is the best storage method, as the plants can withstand freezing temperatures in the air until the ground freezes. Any colder and the greens will wither, and freezing in the ground will change the consistency. It is also reported that frost improves the flavor of turnips
Turnips prefer full sunlight, and a soil pH of 6.5. A loose soil with medium water retention is best. Amend the soil with compost and rotted manure prior to planting your turnip seed. Later, feed regularly with worm casting tea, compost tea or a fertilizer containing higher levels of potassium and phosphorus, which will help with root development. The trace element boron is also helpful to prevent the disease brown heart, though boron can be sprayed separately after planting.
Companion planting is an option for turnips, as they thrive in the company of peas and onions as well as other members of the onion family.
Germination of turnips takes place in less than a week. After sprouting, plants can be thinned if desired, particularly if planting for the root as opposed to the greens. If growing for greens, leave the plants close together, and pick your greens without pulling out the roots. Leaving the plants close together discourages growth of the large bulbous stem, and the greens will replenish consistently. A higher Nitrogen content in the soil encourages production of leaves rather than the root bulb.
If growing for the root bulb, thin the plants out to 3 to 4 inches apart. The shoots that you pull are delicious eaten young in salads, or they can be steamed much like spinach.
In addition to their preference for medium water retention in soil, turnips prefer to be watered deeply before the soil dries out entirely. Frequent shallow watering or erratic watering can bring on early flowering, resulting in poor root development.