Brassica oleracea (Gongylodes Group) 'Kossak'

RHS Plant Profile
kohlrabi 'Kossak'

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kohlrabi 'Kossak' RHS
kohlrabi 'Kossak' RHS
Annual Biennial
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A large, fast-growing white kohlrabi with a mild taste, ready to eat in three months

Position

Full sun

Soil Types

Chalk, Clay, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
1 year
Max Spread
0.1-0.5 metres
Max Height
0.1-0.5 metres

Growing Conditions

Chalk Clay Loam Sand
Moisture
Moist but well–drained
pH
Alkaline or Neutral or Acid

Position

Full sun
Aspect
East–facing or North–facing or South–facing or West–facing
Exposure
Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

  • H1A: under glass all year (>15C)
  • H1B: can be grown outside in the summer (10 - 15)
  • H1C: can be grown outside in the summer (5 - 10)
  • H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
  • H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
  • H4: hardy through most of the UK (-10 to -5)
  • H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
  • H6: hardy in all of UK and northern Europe (-20 to -15)
  • H7: hardy in the severest European continental climates (< -20)
H5

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Brassicaceae
Native to GB/Ireland
No
Foliage
Evergreen
Habit
Tufted
Genus
Brassicas can be annual, biennial or perennial plants, most are upright with alternate, often glaucous leaves, long taproots and clusters of cross-shaped, yellow or white flowers. The genus includes a number of species bred to produce food crops, such as cabbages, turnips, mustards and oilseed rape, as well as others grown for their ornamental value
Name Status
Accepted

How to Grow

Cultivation

Grow in full sun in firm, fertile soil - including coastal regions

Propagation

Propagate by seed. See sowing vegetable seeds

Pruning

No pruning required

Pests

May be susceptible to flea beetle when young, caterpillars of small white butterflies, cabbage root fly and mealy cabbage aphid. Also to pigeons

Diseases

May be susceptible to brassica downy mildew and brassica white blister. In areas where brassicas have been grown before, club root can build up in the soil