Kohlrabi growing - Kohlrabi how to grow, tips, varieties, cooking.
Kohlrabi…. high in vitamin C and K, potassium, fibre as well as the antioxidant carotenoids b-carotene and lutein. Kohlrabis flavour varies between nutty (uncooked) and broccoli with a hint of radish (cooked). If you seek unusual tastes and looks then this give this member of the cabbage family a second glance.
Area of origin:
Kohlrabi sports a rosette of blueish-green leaves above a swollen stem. This almost globe-like stem makes it appear like a turnip growing on a cabbage root. Depending on the variety the edible swollen stem can be green, white or purple.
Are they easy or hard to grow:
Varieties suitable to grow in Ireland:
Lanro (Fast variety to mature with pure white flesh, sweet and tasty)
Kolibri (Great looking purple-skinned roots, pure white flesh, sweet and crunchy, high yields from one of the best varieties for a late season harvest.
Purple Danube (Attractive coloured globes that taste superb)
Logo (Quick maturing, light green kohl rabi ideal for grating into summer salads)
When to grow:
Normally white, green and purple varieties can be sown from March to the end of July. You can even sow from July to the end of August provided it is a purple variety. For all varieties it’s a good idea to make successional sowings, allowing you harvest continually while the veg is young and tender.
Where to grow, and soil conditions required: Kohlrabi will do best in a sunny spot. Shelter is also beneficial. Avoid soil that becomes waterlogged or conversely dries out rapidly.
Relative acidity or alkalinity (Ph) required: Kohlrabi doesn’t grow very well in a strongly acid or strongly alkaline soil. This is because most essential vegetable nutrients in the soil are soluble and available for use at pH levels of 5.5 to 7.5 (slightly acid to neutral). Most vegetables grow best within this range, as is the case with Kohlrabi where 6.5 is about optimum.
If the pH (relative acidity or alkalinity) of your soil is not suited to the vegetable, then soil nutrients such as Nitrogen, Phosphorus, Potassium, iron, boron, copper, manganese and zinc start to become unavailable, leading to poor crops. You can use a simple home soil test available in most garden centres to determine your soils ph. By taking account of the test results you can then decide how much if any amendments are required to bring the to pH of your vegetable garden soil in line.
The application of ground lime will be helpful in countering the excessive acidity. As a rough rule of thumb, an application of 250g of ground lime per metre squared the autumn before planting/sowing will commonly increase your ph by about one point. However as lime is available in different formulations and soil types vary, I advise also consulting the rates set out on the pack.
If you need to decrease your ph to make the soil more acid, then you can apply sulphate of iron at a rate of 100g per metre squared for each drop in ph point. Apply this product according to the manufacturers instructions and heed safety warnings especially those concerning the use of protective clothing and equipment. An application of 2 inches of peat moss worked in to a spades depth all over the proposed growing area will also go a good way towards dropping your soil by one ph point.
Food reserves required:
For long term feeding of your crop, every 10m2 of growing area should have one wheelbarrow load of well-rotted homemade compost or farmyard animal manure spread over its surface sometime during the autumn/early winter before planting/sowing. Dig this in to a spades depth all over the proposed growing area to enrich it for your crop. Whilst digging, remove any stones and other obstacles that might cause the roots to become malformed.
As a rule of thumb, well-rotted manure/compost will be over six months old, and tend to be dark brown will little if any smell. You should not be able to distinguish individual pieces of straw, hay, vegetable peelings, grass etc. as it will all be rotted down.
A week or two before sowing your seed should lightly rake a well-balanced fertilizer into your growing area followed by lightly treading the soil. Growmore or fish blood and bone (organic option) are both suitable for this purpose. Apply according to the rates on the pack.
How to plant or sow:
In your weed-free and lightly raked growing area you must create a ½ inch (1cm) deep drill/trench with the tip of your trowel. Ideally you should drop a seed every 3 inches (7.5cm) along the drill. Close the drill with soil, then water well and label.
Create as many drills as you like at 12-inch (30 cm) intervals. As a rough rule of thumb you can expect about six to seven globes per metre of row, which may help you make a decision on how much to grow. Any seed not required for sowing that year should be kept dry as it has a life expectancy of 4 years.
The expected seed germination time is approx 10 days. Its time for thinning when your seedlings have produced true leaves, those which are the first set of leaves that emerge after the original germination leaves. Thin them to leave a single plant at each 6-inch interval, then water the crop well afterwards. If you have space in your garden you can replant some of the thinnings as a bonus.
Caring for your crop:
Keep the soil around the Kohlrabi weed-free. Take care when weeding because the roots are easily damaged.
Do not allow the plants to dry out as this will result in woody bitter flesh and plant bolting. A mulch of some form helps preserve soil moisture, for example herbicide-free grass clippings.
During a prolonged spell without rain (week or more) you should water gently but deeply once a week. As a rough rule of thumb apply approx 10 litres per metre squared of soil area. Carry out this watering in the morning and try to avoid splashing the leaves, watering the soil instead.
At about the forth or fifth week after seed germination and while plants are growing strongly you can apply a second application of a well balanced fertiliser. Although not essential, a further scattering of Growmore or fish blood and bone can increase the vegetables vigour and make the less susceptible to plant ills. Once scattered the fertiliser should be lightly scratched into the soils surface followed by gentle but deep watering of the soil.
Pests and Diseases:
Kohlrabi being in the same family as cabbage means it can suffer from the same ills as cabbage. However because Kohl rabi matures so quickly it is rarely badly affected.
After sowing provide protection against birds especially if pigeons are a problem in your area. Bird protection should be provided in the form of netting should be used. Fine netting will also prevent butterflies laying their eggs on your crop, which prevents caterpillar damage.
Other troubles of Kohlrabi include…
Harvesting, when and how:
Time from planting to harvest is from 8 to 12 weeks. When the globes are halfway in size between a golf ball and a tennis ball you can grasp the leaves and pull.
Grasp the leaves and carefully lever out the root from beneath with a hand fork, shake off the soil then twist the leaves off rather than cutting them off; thus preventing “bleeding”. No loss of “blood” ensures the beet retains its intense colour and, as claimed by some gardeners its flavour. The leaves or “greens” as they are known can be cooked and eaten like spinach.
For short-term storage (one to four weeks), place Kohlrabi in the salad crisper compartment of your refrigerator. Longer-term, it will keep for four to five months in a area which is cool (2-4 degrees centigrade), dark and away from strong flavours or scents.
To long-term store, cut the globe into cubes, boil for five minutes, remove and place under cold water, then freeze in plastic bags. This will allows you to store them for approx 12 months.
The young leaves can be clipped for eating as steamed greens throughout the season. However be aware that this will set back the growth rate of the globes. So best to have a certain few plants set aside for the clipping practise.
Young Kohlrabi globes are nice steamed, no need for peeling like this either.
For more mature ones you can peel off the outer skin, then dice and boil for eating with potatoes. Serve mashed with a little melted butter and/or cream
Boiled lightly your whole kohl rabi can be cut into strips and tossed in an oil and vinegar dressing. Chill to serve with cold ham or other meats.
Young Kohlrabi can also be served like this, uncooked, nice and crispy. Add it to coleslaw or grate it over salads for a nutty/turnip/cabbage taste.
Uncooked cubed or strip kohlrabi can be introduced to a stirfry near the end of cooking, adding crunch and flavour.
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