Alnus rubra (Red alder)

Botanical name

Alnus rubra

Other names

Red alder, Western alder, Oregon alder

Genus

Alnus Alnus

Species

A. rubra - A. rubra is a medium sized, upright, fast growing tree with large, green leaves and good autumn colour. It has catkins that decorate the tree from late autumn until spring.

Foliage

Deciduous

Habit

Conical

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Colour

Flower

Pale-yellow in Winter

Foliage

Green in Spring; Dark-green in Summer; Yellow in Autumn

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How to care

Watch out for

Specific pests

Alder sucker , Leaf-mining sawflies

Specific diseases

Bark canker

General care

Propagation methods

Hardwood cuttings, Seed

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Monthly care advice

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Where to grow

Alnus rubra (Red alder) will reach a height of 25m and a spread of 10m after 20-50 years.

Suggested uses

Hedging/Screens, Low Maintenance, Wildlife, Waterside, Resistant to pollution

Cultivation

Thrives in poor, wet conditions.

Soil type

Chalky, Clay, Loamy

Soil drainage

Boggy damp conditions, Moist but well-drained, Well-drained

Soil pH

Acid, Alkaline, Neutral

Light

Partial Shade, Full Sun

Aspect

North, South, East, West

Exposure

Exposed, Sheltered

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

Hardy (H4)

USDA zones

Zone 10, Zone 9, Zone 8, Zone 7, Zone 6, Zone 5

Defra's Risk register #1

Plant name

Alnus rubra (Red alder)

Common pest name

Scientific pest name

Melampsoridium hiratsukanum

Type

Fungus

Current status in UK

Present (Limited)

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

5

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

4

General biosecurity comments

Pathogen of alder; established in the UK and elsewhere.

Defra's Risk register #2

Plant name

Alnus rubra (Red alder)

Common pest name

Alder bleeding canker; Alder Phytophthora root disease

Scientific pest name

Phytophthora alni

Type

Oomycete

Current status in UK

Present (Widespread)

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

4

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

4

General biosecurity comments

Damaging pathogen of Alder; first detected in the UK in 1993; which has subsequently spread to most areas. Alders are important in the context of watercourse management. No prospect of eradication or containment but possible co-ordinated action to mitigate impacts to be considered with stakeholders.

Defra's Risk register #3

Plant name

Alnus rubra (Red alder)

Common pest name

Scientific pest name

Phytophthora siskiyouensis

Type

Oomycete

Current status in UK

Present (Unknown Distribution)

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

3

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

4

General biosecurity comments

Pathogen causing disease of Alder and other tree species in the USA and Australia; now detected in the UK. Could possibly be mistaken for P. alni. A PRA will help to better assess the risk to the UK.

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/