Introduction: It is probable that the turnip was domesticated independently in two different places. Somewhere in the vicinity of Afghanistan and in the Eastern Mediterranean. It has been grown in both those areas for several thousand years.
In Europe the large swollen roots have been grown for centuries as food for animals and poor humans. They were scorned by the better off classes as only fit for animals and still carry a slight stigma to this day.
In Asia the turnip is looked upon quite differently and is a very important crop in both China and Japan. In those countries a whole range of varieties exist.
Turnip is best known for its swollen root, but may also be grown for the tasty and nutritious leaves. Some varieties have been developed that produce an abundance of tender foliage.
Nutritional content: The roots contain vitamin C, complex carbohydrates, soluble fiber, calcium, magnesium, potassium, lysine and tryptophan. They contain around 130 calories per pound.
The leaves are rich in vitamins A, C and K, chlorophyll and some important phytochemicals (including isothiocyanates).
Crop value: Turnips are a fast growing (40 – 50 days), hardy and easily grown multi- purpose crop that is quite useful for the homesteader. The roots provide a substantial root vegetable, the leaves are nutritious greens, the flower buds can be used like broccoli (they are popular in Italy under the name broccoli raab) and the seeds can be sprouted like cress or alfalfa. It is also a good source of feed for livestock.
Germ temp: 40 (60 – 85) 90°F
Germ time: 1 – 5 days
5 days at 50°F
3 days at 59°F
2 days at 68°F
1 day at 77°F * Optimum
Seed viability: 3 years
Germination percentage: 75%+
Growing temp: 40 (60 – 65) 85°F
Plants per person: 5
Plants per sq ft: 9
Direct sow: 2 – 4 weeks before last frost
Fall crop: Plant 8 – 10 weeks before first fall frost
Days to harvest: 40 – 80
Yield per plant: 3 – 16 oz
Yield per sq ft: 2 – 4 lb
Ease of growing: Turnip is a cool season biennial and in a suitable climate it is pretty easy to grow.
Turnip is most satisfactory as a fall crop, as the swollen roots can mature in the cool weather which develops their best flavor. It is less useful in spring, as warm temperatures make the roots less palatable and can also cause them to bolt.
Climate: Turnip is happiest when growing in a cool (60 to 65°F) and humid climate. Older plants are quite hardy and many types can tolerate severe frost.
pH 6.0 (6.8) 7.5
Turnips need to grow quickly for best quality. This requires a rich, loose, well-drained, but moisture retentive soil. Brassicas in general do well on neutral, or even somewhat alkaline soil. If clubroot is a problem you should keep the soil pH above 6.5.
Like other Brassicas, turnips are vulnerable to boron deficiency, but this shouldn’t be a problem if you add lots of organic matter.
Soil preparation: Like most root crops turnips prefer a loose soil. If the soil is heavy, or compacted, it can be loosened by incorporating 2˝ of compost or aged manure. Double digging is also very beneficial. A good practice is to plant turnips on soil that was thoroughly dug and manured for a previous crop (such as potatoes).
Turnips don’t require a lot of nitrogen (unless you are growing them for greens) as this encourages foliage growth rather than root growth. However if the soil is poor you may want to give them some fertilizer mix. You may also want to give them lime, as it supplies calcium and decreases acidity.
Where: If you are growing turnips for their roots they will need full sun. Those grown for their leaves will do quite well in part shade.
Crop rotation: Don’t plant turnips where another Brassica crop has grown in the last 3 years.
When: Turnip really needs cool nights to encourage it to store sugars in the root. If nights are too warm it will use those sugars for growth instead. This can make the roots pungent and quite unpleasant. Of course the only way you can get cool nights is by planting at the right time.
Spring: Biennial root crops store food in their roots as preparation for the coming winter. When you plant them in spring you are going against this natural inclination, so they tend not to do so well.
Spring isn’t the ideal time to plant turnips because the weather gets warmer as they mature, which is the reverse of what you want. It’s only worth planting them in spring if they have time to mature before the temperatures start to rise above 60 – 65°F (and nights are still cool).
Turnip can survive temperatures of 25°F and can be sown as soon as the soil can be worked in the spring (when it may only be 45°F). However it’s generally better to wait until perhaps 4 weeks before the last spring frost. The first plantings may be grown under cloches to speed up their growth.
Fall Turnips do much better as a fall crop, as they have guaranteed cool weather when they are maturing and there are less problems with insect pests.
They are usually planted from late summer onward, maybe 8 – 10 weeks before the first fall frost date (the actual planting date depending upon when the weather starts to cool down). You want them to reach maturity just before it starts to get cold. Then it won’t matter when growth starts to slow down. A few freezes will even improve their flavor.
Winter: In northern Europe fall planted turnips were once an important winter crop.
You can also plant turnips in the fall, for use the following spring as broccoli raab or spring greens.
Succession sowing: You don’t need many turnip plants at one time. Sow a few seeds every 2 weeks, rather than a large number all at once. The exception to this would be a fall planting for storage, or over- wintering in the ground.
Direct sowing: Like most root crops, turnips don’t transplant well, so they are almost always direct sown. The seed germinates easily at low temperatures and the hardy plants grows rapidly. They can be broadcast or sown in drills (shallow furrows). Sow the seeds ¼ – ½˝ deep and 1˝ apart.
Beds: Space the plants 4 – 6˝ apart in the intensive beds.
Rows: If growing in rows, space the plants 3 – 6˝ apart, with 18 – 24˝ between the rows.
The best turnips are those that have grown rapidly, which can only occur if the plants have everything they need in the way of nutrients, light and water.
Thinning: Like other direct sown root crops, they need careful thinning and weeding. Use the thinnings in the kitchen.
Fertilization: Give the plants a feed of compost tea, or liquid kelp, once they get going (remember, not too much nitrogen).
Water: Turnips don’t need a lot of water, but it should be available constantly and not fluctuate too much. If the soil gets too dry, they can get woody and may even bolt. Irregular watering can cause the roots to crack.
Mulch: This is useful to prevent the soil drying out, to suppress weeds, to keep the soil cool and to supply nutrients.
A deep mulch of straw is helpful in winter to prevent the soil from freezing.
Bolting: Though the turnip is a biennial it will bolt in its first year in some circumstances.
The usual reason for bolting in turnips is stress caused by lack of water or nutrients, careless transplanting, or warm weather. It is natural for plants to bolt in the spring of their second year. It is what they are supposed to do.
Pests and disease: Turnips are close relatives of the cabbages and are vulnerable to the same pests and diseases (of which there are a considerable number.) Flea beetles and aphids have been the commonest problems for me, though usually there is no need to do anything about them, as these vigorous plants can handle them.
Roots: Spring roots should be harvested when they are still quite small, from 1½ – 3˝ in diameter (this can sometimes be within a few weeks of sowing). When they get bigger than this they usually start to turn woody.
Winter roots can be harvested when somewhat larger, as they stay in much better condition in the cold weather. They are at their best after their tops have been killed by frost.
After pulling the root you should remove the tops (leave about 1˝ of stem) so they don’t draw moisture from the root. If the tops aren’t too tough you can use them as a green vegetable.
Leaves: If you are growing turnips for the tender young foliage, it can be harvested as needed. As with the roots, the leaves also taste better in cool weather.
It is best to gather single leaves as they get large enough. Don’t take them from the growing point and only take 1 or 2 leaves from a plant at one time, so it can continue to grow strongly.
Storage: In milder areas the roots can be left in the ground and harvested as needed (cover with mulch if it gets too cold). If the roots freeze you want them to stay frozen, so cover with thick mulch. Repeated freezing and thawing will cause them to rot.
Some people say leaving the roots in the ground through the winter is not a good idea as it may help Brassica pests to winter over. They advocate harvesting all of the roots in early winter and storing them in a root cellar at 34 – 40°F (if it’s warmer than this they will eventually start growing). They can also be stored outside in a clamp (see Potato).
The root can be cut into cubes and frozen or canned (I can’t say canned turnip has much appeal for me though). In the Middle East and Japan the roots are popular pickled.
Seed saving: Turnip is cross-pollinated by insects, so only one variety should be flowering at a time (or they should be caged or isolated by a half mile).
The usual method of obtaining seed is to plant it in late summer, protect it over the winter (inside or outside) and allow it to flower in spring. It should be planted in a block so insects are likely to visit many plants without going to other plants nearby. Collect the dry pods when they are ripe (they shatter easily so watch carefully), sift out the seeds, dry further and store.
In milder areas turnips may self-seed if given the opportunity.
Forcing: Any surplus roots can be potted up and forced like those of chicory, for winter greens.
In England and Japan, where turnips are popular, they have different varieties for early and late planting, as well as some very dependable F1 hybrids.
These are sometimes grown for greens as well as their roots.
Purple Top White Globe: The old standard (55 days).
Purple Top Milan – Italian heirloom with white flesh (50 days).
Snowball – Beautiful white roots (40 days).
These are prized for the edible root.
Yellow/Amber Globe – Heirloom from prior to 1840 (60 days)
Golden Ball – Outstanding flavor (50-60 days).
These grow fast and are almost like large radishes. They are quite good raw and are often steamed or stir fried. Good root types include:
Tokyo Cross F1
Nozawana is grown for its leaves.
Shogoin: A dual purpose crop grown for leafy greens or roots.
Seven Top: Important in the southeastern states for turnip greens. It can also be used for broccoli raab.
Tendergreen: This leaf variety is often thought of as a mustard and is treated like one, but it is actually a turnip.
Small turnip roots (about 1½˝ diameter) can be eaten raw as a substitute for radish. They are actually milder and better flavored than most radishes. Cooking turnip can be tricky, under-cooking is definitely better than over-cooking, which can turn them into watery mush.
The flowers and immature seedpods are a tasty minor additions to salads.
In this country this Italian delicacy can be found in markets catering to Italian communities or foodies. The word raab means turnip, so the name means (logically enough) turnip broccoli. This is a pretty good description of the edible flower stalks it produces.
This isn’t a highly productive crop, but it is a welcome one when it appears in early spring, when the garden often has little else to offer. It is grown in the same way as root turnip, with the aim of producing as big a root as possible (there is no worry about it getting tough).
Fall: The best time to plant broccoli raab is in late summer or fall, to mature the following spring. If it gets very cold, cover the plants with mulch to protect them, as they may die if it gets too cold. In early spring the plants bolt and send up slender flower stems. These aren’t nearly as large as broccoli heads, but are used in much the same ways. The top 6 – 8˝ of stem is cut before the flower buds open and is steamed or eaten raw. The plant will then produce more usable side shoots.
Spring: Broccoli raab can also be planted as a spring crop (it will act like an annual, rather than a biennial), started 4 weeks before the last frost date, though it doesn’t usually do as well. When planted at the right time it will grow fast and mature in as little as 5 weeks. In cool climates it may be succession sown several times.
Varieties: There aren’t many, though new ones are appearing.