Speckled alder

Leaves of speckled alder.

Speckled alder is a smaller tree that is appropriate for planting under power lines. Early spring flowers are interesting, but not really showy. This tree may be difficult to find in local nurseries.

This species is native to the Chicago region according to Swink and Wilhelm's Plants of the Chicago Region, with updates made according to current research.  

Botanical name:

Alnus incana subsp. rugosa

All Common Names:

speckled alder

Family (English):

Birch

Family (Botanic):

Betulaceae

Tree or Plant Type:

  • Shrub,
  • Tree

Foliage:

  • Deciduous (seasonally loses leaves)

Native Locale:

  • Chicago area,
  • Illinois,
  • North America

Planting Site:

  • Residential and parks,
  • Under utility lines

Landscape Uses:

  • Hedge,
  • Massing,
  • Screen,
  • Utility

Size Range:

  • Small tree (15-25 feet),
  • Compact tree (10-15 feet),
  • Large shrub (more than 8 feet)

Mature Height:

15-25 feet

Mature Width:

15-25 feet

Light Exposure:

  • Full sun (6 hrs direct light daily),
  • Partial sun/shade (4-6 hrs light daily)

Hardiness Zones:

  • Zone 3,
  • Zone 4,
  • Zone 5 (Chicago),
  • Zone 6

Soil Preference:

  • Moist, well-drained soil,
  • Wet soil

Acid Soils:

  • Tolerant

Alkaline Soils:

  • Intolerant

Salt Spray:

  • Moderately Tolerant

Soil Salt:

  • Intolerant

Drought Conditions:

  • Moderately Tolerant

Poor Drainage:

  • Tolerant

Planting Considerations:

  • May be difficult to find in nurseries

Ornamental Interest:

  • Spring blossoms,
  • Persistent fruit/seeds,
  • Attractive bark

Season of Interest:

  • Early winter,
  • Mid winter,
  • Late winter

Flower Color & Fragrance:

  • Inconspicuous

Shape or Form:

  • Multi-stemmed

Growth Rate:

  • Moderate,
  • Fast

Transplants Well:

  • Yes

Wildlife:

  • Browsers,
  • Small mammals,
  • Songbirds

More Information:

Tree & Plant Care

This species is best in moist sites and is able to tolerate short-term flooding.

Disease, pests, and problems

Potential problems include cankers, alder aphids, Japanese beetles, and leaf miners.

Native geographic location and habitat

C-Value: 8

Bark color and texture 

Bark is smooth, dotted with warty lenticels.

Leaf or needle arrangement, size, shape, and texture

The oval leaves are 2 to 4 inches long and alternately arranged.  The edges of the leaves are doubly-toothed.  The upper leaf surface is dull green and the lower surface is grayish.  Little color change in fall.

Flower arrangement, shape, and size

Male flowers in dangling catkins, yellow-red, in early spring before leaves appear.  Female flowers small, pink, egg-shaped.

Fruit, cone, nut, and seed descriptions

Fruit are cone-like structures.

Location of Alnus incana subsp. rugosa (Speckled alder) at the Arboretum