Brassica napus var pabularia
Introduction: As you might guess from the name, this plant originated in Northeastern Europe and neighboring Asia. It is an entirely different species from Scotch kale, but is often grouped together with it. This is understandable as they are both called kale, are both Brassicas and are grown and used in the same ways. However they differ in that most Siberian kales aren’t as hardy, they have thinner leaves and they taste better in warm weather.
I think Siberian kale is a better food plant than Scotch Kale. It is milder in flavor and so tender in texture that it is sometimes used raw in salads. It is a fantastic home garden crop plant, very hardy, nutritious, tasty and easy to grow. I can’t praise it enough.
In Britain this species is known as rape kale, which is a good name because it is actually a type of rape (B. napus) and more closely related to rutabaga than to Scotch kale.
Nutritional content: This plant is rich in all of the nutrients you would expect to find in the Brassicas. These include vitamins A, C and K, chlorophyll, manganese, copper and several important antioxidants. The red colored types are particularly valuable because the red color comes from beneficial carotenoids.
Crop value: This plant is a staple winter green vegetable in my garden. I have planted it in late spring (if you plant it too early it will bolt almost immediately) and it has fed us through the summer, fall, winter (in our mild winters it doesn’t even slow down) and into early spring. It then bolts and produces an abundance of nutritious and tasty flower buds that can be used like broccoli (if they are infested with aphids, blast them off with a jet of water). Eventually the flowers open and go on to produce a lot of seed (often several ounces per plant). This can be used for sprouting, micro-greens and to grow future crops.
This species is good to eat at any time, though it is at its best in cool weather, when the leaves become sweeter in flavor. It is also most useful at that time, when fewer other leafy crops are available.
pH 6.0 – 7.5
Kale is more tolerant of poor soil than other Brassicas, but the most palatable leaves are produced by rapid uninterrupted growth. For this the soil must be rich, well-drained and moisture retentive with lots of organic matter. Of course with a winter crop, drainage is usually more of a concern than water retention. If the soil is too wet in winter the roots may rot.
Soil preparation: Kale likes organic matter, so amend the soil by digging in 2˝ of compost or aged manure. It also likes a neutral pH, so add lime to raise the pH if necessary. Its nutritional requirements are similar to those of cabbage, in that it needs a significant amount of phosphorus and potassium, but not a lot of nitrogen. If your soil isn’t very fertile you may also want to add some fertilizer mix.
| About Kale |
Germ temp: 40 (45 – 95) 95°F
Germination time: 4 – 9 days
15 days / 50°F
9 days / 59°F
6 days / 68°F
5 days / 77°F * Optimum
4 days / 86°F
Seed viability: 4 – 6 years
Germination percentage: 75+
Weeks to grow transplants 5 – 6
Growing temp: 40 (60 – 65) 75°F
Plants per person: 10
Plants per sq ft: to 1
Height: 24 – 48˝
Spread: 18 – 36˝
Start: 6 wks before last frost
Plant out: 2 wks before last frost
Direct sow: Spring: 4 – 6 wks before last frost
Fall: 2 wks before first frost
Days to harvest: 50 – 70 days from transplant
80 – 100 days from seed
Harvest period: 16 – 26 weeks
Yield per plant: 1 – 2 lb
Where: Winter kale will be growing in the coldest part of the year, so should be planted in the warmest, sunniest, most sheltered part of the garden.
Kale is one of the most shade tolerant garden vegetables, though it won’t be quite as productive as when in full sun. In warmer weather it is usually happier in light shade. If this is from a deciduous tree, it will mostly disappear in winter, which is ideal.
Crop rotation: Kale should not be planted where another Brassica has grown in the past 3 years.
Spring: Kale can be planted in spring for harvesting in early summer. It is started indoors 6 weeks before the last frost date and planted out 2 weeks before the last frost date. If you plant too early the plants can be vernalized and may bolt soon after planting out.
Kale will actually grow right through the summer, but doesn’t taste very good in warm weather. It really needs cool weather to make it tender and sweet.
Fall: As I already mentioned kale is most useful as a fall crop, planted in mid-summer, at least 2 – 3 months before the first fall frost date. The plants need to be fairly big by the time of the first frost, so they are vigorous enough to keep growing. In mild climates it will continue to grow all winter without disruption and can be harvested continually for months (it will also be in peak condition in the cool weather).
It is a good idea to plant your autumn kale as an intercrop between an existing summer crop. It will gradually take over the space as the weather gets cooler and the summer crop fades.
Late kale can succeed a mid-season crop such as potatoes or beans.
Winter: Your fall kale crop will gradually become your winter kale crop, especially in milder areas. If you want to use kale as a staple winter crop you should probably grow quite a lot of it. It grows slowly in winter, so you want to have quite a few plants to harvest from (so you don’t stress any one plant too much).
Direct sowing: The easiest way to grow kale is to sow it directly into the garden. The seed germinates easily and grows quickly, even in fairly cool soil. Plant the seeds ¼ – ½˝ deep and 2˝ apart. Start harvest thinning when all the seedlings have emerged and are of sufficient size.
Starting inside: Kale is often started indoors to get an earlier crop in spring. It will germinate and grow much faster in warmer conditions, enabling you to plant out a thriving seedling, rather than a seed. Transplants may also be used where insects or other pests are a problem.
Kale doesn’t mind transplanting so can be started in flats, as well as cell packs and soil blocks. Plant the seed 1˝ apart in a flat and when the seedlings are big enough prick out into another flat, leaving 2˝ between the plants. The plants are ready to go outside when they have 3 – 5 true leaves, a stem diameter of about ⅛˝ and are 3 – 5˝ tall.
Hardening off: If transplants are to go outside while it is still cold, they should be hardened off first. They will then tolerate temperatures as low as 25˚F. You do this by putting the plants outside for 2 hours on the first day, then
4 hours on the second day. Add 2 hours every day for a week and then plant out.
A simpler alternative is to put them in a cold frame, which is opened for longer periods each day and closed at night.
Planting out: Transplant the seedlings slightly deeper than they grew in the flats, up to the depth of their first true leaves. Water well after planting (of course).
Protection: Early growth is often slow in cool weather. You might want to use cloches to keep the plants warmer and so speed this up.
Bolting: In spring a potential problem with using transplants may occur if you are too successful and grow big healthy transplants. If these are then exposed to cold weather they may be vernalized, which will cause them to bolt. To avoid this your transplants should have stems no thicker than ⅛˝.
Starting transplants outside: In terms of bed space, a kale seed takes up as much space as an 8 week old transplant, so direct sowing isn’t very space efficient. You can use bed space more efficiently by sowing your fall kale in an outdoor nursery bed (this only works in warm weather of course). Leave them there until they are of transplant size and then plant them out at their full spacing in early fall.
Spacing: Kale plants can get quite big, so give them plenty of room:
12˝ apart in excellent soil
15˝ apart in good soil
18˝ apart in poor soil
Rows: If you want to plant in rows, space them 18 – 24˝ apart, with 12˝ between the plants.
Weeds: Kale is pretty independent once established, so you only really need worry about weeds while it is young.
Watering: Kale has large leaves and can lose a lot of water in warm weather (another reason not to grow it then). It is actually moderately drought tolerant, but for the best quality (texture and flavor) you must keep it well supplied with water.
Fertilization: If the soil isn’t very fertile, feed the plants with compost tea or liquid kelp. Start feeding them as soon as they have recovered from transplanting and every month thereafter. This is especially important if you are going to be harvesting for weeks on end.
Mulching: Use a mulch in summer to keep down weeds, keep the soil cool and conserve soil moisture. In winter a mulch can help to protect the roots by moderating soil temperature and preventing frost heaving.
Pests and diseases: Kale is less vulnerable to pests than other Brassicas (even to clubroot), but it still has its share, especially in warm weather (aphids are the commonest). See Cabbage for more on these pests and how to deal with them.
Birds In my garden quail have a particular affection for Brassicas such as kale and they may strip whole leaves from the plants. In my last garden they got so bad in winter that I had to net the 4 ft tall plants.
When: Kale produces an abundance of foliage right through the growing season, but it is at its best during cold weather.
You can gather kale leaves for as long as they are produced, sometimes right through the winter. In extreme cold you might cover them with mulch for extra protection. Even the frozen leaves can be eaten and are actually very good.
The new shoots, produced when the plant first starts growing again in spring, are also good.
When kale bolts in spring, the flower buds can (and should) be gathered and used like broccoli. They are a nutritious and tasty treat, that is not to be missed. If they are infested with aphids, blast them off with a jet of water.
How: For a longer and bigger harvest 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.
You may be able to stimulate an old plant to put out tender new growth, by stripping off all of its leaves.
Seed saving: Plants over-wintered in the ground will flower the following spring. Kale will cross-pollinate with any other Brassica crop (broccoli, Brussels sprout, cabbage, collards), so only one variety can be flowering at one time. Save the seed in the same way as you would cabbage.
The plants will produce an abundance of seed. In fact they sometimes get so top heavy with seed they need staking to stop them falling over.
If you save kale seed you will end up with a lot, especially as you should save the seed from at least 5 plants to maintain some genetic variability. This is far more than you will ever need for planting. You can sprout most of it like alfalfa, or use it to grow micro-greens.
Unusual growing ideas
Winter indoors: In very cold areas kale can be grown in winter in an unheated greenhouse or cold frame. It has even been grown indoors as a winter houseplant.
Ornamental use: Some kales have very attractive foliage and can be used in the flower garden. The specially bred ornamental kales are edible too and can be quite good.
Container growing: Kale does well in containers, so long as it has enough room, good soil and plenty of water.
Growing as a perennial: You can get some of the hardier kale varieties to survive for several years, by not allowing them to flower and set seed. You can propagate them by taking green stem cuttings in summer.
Cover crop: Kale is sometimes planted as a green manure or winter cover crop. In areas with mild winters it will produce a lot of foliage over the winter and has the additional benefit that it is edible. In spring you can eat the tender new flower shoots, before incorporating the rest of the plants into the soil.
The drawback to using kale as a cover crop is that it is a member of the Brassica family and so prone to all of the same pests and diseases.
Seed saving: This species won’t easily cross-pollinate with any B. oleracea species, though it will cross with rutabaga. When collecting seed take it from a minimum of 10 of the best plants (remove any poor specimens to prevent them from pollinating the plants you want).
Varieties: This is such a wonderful crop plant it’s becoming increasingly popular with vegetable gardeners and quite a lot of new (and old heirloom) varieties are now becoming available. Some of the most interesting include:
Siberian Kale – Tender enough to be good raw as well as cooked.
Dwarf Siberian Kale – A smaller variation of the above.
White Russian – A hardy type that also tolerates wetter soil than most.
Wild Kale – A very variable type.
Red Russian: 60 days. This old Russian heirloom is also known as Ragged Jack (because of its ragged frilled leaves). It grows well in heat and cold, though is not as hardy as some cultivars. It is one of the best flavored varieties, with succulent and tender leaves.
Western Front – One of hardiest varieties and if you pamper it a bit, it can even be convinced it is a short lived perennial.
These kales tend to be more tender than the Scotch types and don’t need cooking for as long. In fact many are good raw too.
| Colcannon |
This simple Irish peasant dish was traditionally eaten at Halloween.
1 lb kale (strip out any tough midribs and chop finely)
1 lb mashed potatoes
1 finely chopped onion or 2 small leeks or 4 chopped scallions
5 fl oz milk
Cook the kale until tender. At the same time simmer the onions in the
milk for 5 minutes. Mix the finely chopped kale with the mashed potatoes and then add the milk. Reheat for a few minutes then put in a dish.
Sprinkle with salt and pepper and then make a well in the center for the butter.