ALDERS
Alnus species

Height: 15-50'
Width: 15-30'
Hardiness Zone: 3a
Exposure: Full sun or partial shade
Origin: North America, Europe

Description:

Alders are large shrubs or small to medium sized trees. They have unusual fruiting structures (strobili) that resemble small, dark brown pine cones. These are some of the most commonly available alder species:

• European Alder (Alnus glutinosa) is a medium sized tree with a narrow pyramidal crown. It grows rapidly and often develops an irregular form. Foliage is clean, glossy dark green.
   
• White (or Gray) Alder (Alnus incana) has a pyramidal to oval form and grows to 30-50' tall. Foliage is dark green. Native to Europe, it is very cold hardy and does well in wet sites.
   
• Speckled Alder (Alnus rugosa) is native in boggy areas in the Great Lakes region. It is a large, upright growing shrub about 12-15' in height. Good choice for naturalistic plantings near ponds and streams.

Site and Cultural Requirements:

Alders grow naturally in bogs or along stream banks where the soil is often quite wet so they are good choices for damp landscape sites. They also grow in well-drained soils but do not tolerate drought conditions. Alders tolerate a range of soil pH and generally perform well in poor, infertile soils. Alders can be somewhat short lived, especially if grown in very dry, compacted sites.

Insect/Disease Issues:

Generally trouble-free, though alder psyllid, alder blight aphid, and tent caterpillars can cause damage to the foliage.

Cultivars:

• European Alder (Alnus glutinosa) cvs. include cutleaf 'Laciniata' and strongly upright ‘Pyramidalis’ (syn. ‘Fastigiata’)
• White (or Gray) Alder (Alnus incana) cvs. include cutleaf 'Laciniata' and weeping 'Pendula'

We would like to thank the Landscape Plant Development Center and Minnesota Landscape Arboretum for the botanical information and photos.

 

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Phone: (515)-992-4211
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