Allium cepa (Cepa Group) 'Keravel'

RHS Plant Profile
onion 'Keravel'

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Synonyms

Allium cepa 'Rose of Roscoff'

Herbs - Culinary Bulbs
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A bulbous perennial grown as a vegetable with upright, blueish-green leaves. Medium-sized, rounded bulbs with pinkish flesh and brown-pink skins with a sweet aroma and flavour. A French Heritage variety which stores well

Position

Full sun

Soil Types

Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
1–2 years
Max Spread
0.1-0.5 metres
Max Height
0.1-0.5 metres

Growing Conditions

Loam Sand
Moisture
Well–drained
pH
Alkaline or Neutral

Position

Full sun
Aspect
South–facing or West–facing
Exposure
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)
H4

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Amaryllidaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Clump forming
Genus
Allium are bulbous herbaceous perennials with a strong onion or garlic scent, linear, strap-shaped or cylindrical basal leaves and star-shaped or bell-shaped flowers in an umbel on a leafless stem
Name Status
Accepted

How to Grow

Cultivation

Grow in free-draining, fertile soil in full sun. Keep well watered in dry periods but stop watering when bulbs become swollen

Propagation

Propagate by seed or by onion sets. See how to grow: onions or sowing vegetable seeds

Suggested planting locations and garden types

  • City and courtyard gardens
  • Cottage and informal garden
  • Flower borders and beds

Pruning

Remove any flowerheads that appear. Harvest when leaves fade to yellow and droop

Pests

May be susceptible to stem and bulb eelworm, leek moth and onion fly

Diseases

May be susceptible to rusts