Allium sphaerocephalon (Roundhead leek)

Botanical name

Allium sphaerocephalon

Other names

Roundhead leek, Round-headed allium

Genus

Allium Allium

Species

A. sphaerocephalon - A. sphaerocephalon is a bulbous perennial with strap-like, mid-green basal leaves and tall stems bearing small round or oval pink to purple-red flowerheads in summer

Foliage

Deciduous

Habit

Erect, Spreading

Awards

RHS AGM (Award of Garden Merit)

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Colour

Flower

Reddish-purple, Pink in Summer

Foliage

Mid-green in Spring; Mid-green in Summer

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How to care

Watch out for

Specific diseases

Downy mildew , Onion rot

General care

Propagation methods

Division, Seed

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Monthly care advice

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Where to grow

Allium sphaerocephalon (Roundhead leek) will reach a height of 0.9m and a spread of 0.1m after 2-5 years.

Suggested uses

Architectural, Beds and borders, Cottage/Informal, Flower Arranging, Gravel, Underplanting

Cultivation

Grows in fertile, well-drained soil. Add grit to clay soils to improve drainage.

Soil type

Chalky, Clay, Loamy, Sandy (will tolerate most soil types)

Soil drainage

Moist but well-drained, Well-drained

Soil pH

Acid, Alkaline, Neutral

Light

Full Sun

Aspect

North, South, East, West

Exposure

Sheltered

UK hardiness Note: We are working to update our ratings. Thanks for your patience.

Hardy (H4)

USDA zones

Zone 9, Zone 8, Zone 7, Zone 6

Defra's Risk register #1

Plant name

Allium sphaerocephalon (Roundhead leek)

Common pest name

allium leaf miner

Scientific pest name

Phytomyza gymnostoma

Type

Insect

Current status in UK

Present (Limited)

Likelihood to spread in UK (1 is very low - 5 is very high)

3

Impact (1 is very low - 5 is very high)

3

General biosecurity comments

Pest of Allium already present in UK and spreading; previous consultation supported awareness raising only; industry should prepare for the event of findings in commercial crops.

Defra's Risk register #2

Plant name

Allium sphaerocephalon (Roundhead leek)

Common pest name

Asain cotton leafworm; Cluster caterpillar; Fall armyworm; Rice cutworm; Taro caterpiller; Tobacco budworm; Tobacco caterpillar; Tobacco cutworm; Tobacco leaf caterpillar

Scientific pest name

Spodoptera litura

Type

Insect

Current status in UK

Absent

Likelihood to spread to UK (1 is very low - 5 is very high)

3

Impact (1 is very low - 5 is very high)

3

General biosecurity comments

Regulated pest; frequently intercepted with occasional outbreaks which have been successfully eradicated in the UK.

Defra's Risk register #3

Plant name

Allium sphaerocephalon (Roundhead leek)

Common pest name

Nematode; common spiral; Spiral nematode; Steiners spiral nematode

Scientific pest name

Helicotylenchus dihystera

Type

Nematode

Current status in UK

Absent

Likelihood to spread to UK (1 is very low - 5 is very high)

2

Impact (1 is very low - 5 is very high)

3

General biosecurity comments

Nematode pest unlikely to be very damaging in its own right; but used as a an indicator species to assess compliance of soil requirements of imported plants to be kept under review in light of EFSA evaluation of soil requirements.

About this section

Our plants are under greater threat than ever before. There is increasing movement of plants and other material traded from an increasing variety of sources. This increases the chances of exotic pests arriving with imported goods and travellers, as well as by natural means. Shoot is working with Defra to help members to do their part in preventing the introduction and spread of invasive risks.

Traveling or importing plants? Please read "Don't risk it" advice here

Suspected outbreak? Click here for contact details to report to the relevant authority.

Date updated: 7^th March 2019 For more information visit: https://planthealthportal.defra.gov.uk/