Allium cepa Proliferum Group (Tree onion)

Botanical name

Allium cepa Proliferum Group

Other names

Tree onion, Egyptian onion, Walking onion, Topsetting onion, Allium cepa var. proliferum, Allium x proliferum, Allium cepa 'Proliferum'

Genus

Allium Allium

Variety or Cultivar

Proliferum Group _ Proliferum Group is a perennial cultivated as an annual vegetable with upright, strap-like, dark grey-green leaves and clusters of small, edible bulbs forming at the top of the stems, typically ready for harvest in late summer.

Foliage

Deciduous

Habit

Upright

Toxicity

Can be toxic if consumed in large quantities. Toxic to mammals, particularly dogs.

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Colour

Foliage

Dark-green in Spring; Dark-green in Summer; Dark-green in Winter

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How to care

Watch out for

Pests

Purported to be immune to onion fly. Highly attractive to slugs.

Specific pests

Leek moth , Eelworm (stem and bulb) , Slugs

Diseases

Good tolerance to mildew.

Specific diseases

Bolting , Bull neck , Neck rot , Rust , Saddleback , Shanking , Smut , White rot , White tip

General care

Pruning

Harvest in late summer. Replant immediately or store in a cool, dry, frost-free place and plant out in late winter or early spring. Divide bulbs after leaves die back in late summer.

Propagation

Typically grown from sets, which are quick maturing, adaptable, and less prone to mildew and onion fly. If growing from seed, sow seed in rows from late winter to mid-spring. Think out weak seedlings.

Propagation methods

Seed, Sets

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Monthly care advice

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Where to grow

Allium cepa Proliferum Group (Tree onion) will reach a height of 1.2m and a spread of 0.5m after 1-2 years.

Suggested uses

Add to salads, Beds and borders, Flavouring food and drinks

Cultivation

Plant sets 10cm apart in rows 30cm apart in autumn. Push fairly deep into the soil, deeper than other edible onion sets. Water in dry periods. Stop watering when onions are swollen. Best to rotate site annually. Avoid planting near alfalfa.

Soil type

Loamy, Sandy

Soil drainage

Well-drained

Soil pH

Alkaline, Neutral

Light

Full Sun

Aspect

South, West

Exposure

Sheltered

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

Tender in frost (H3)

Defra's Risk register #1

Plant name

Allium cepa Proliferum Group (Tree onion)

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 cepa Proliferum Group (Tree onion)

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 cepa Proliferum Group (Tree onion)

Common pest name

American serpentine leaf miner; chrysanthemum leaf miner

Scientific pest name

Liriomyza trifolii

Type

Insect

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

Regulated pest already subject to review at the EU level (2013). Regularly intercepted in the trade.

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/