Guide to NJ Alders

There are three Alders (Alnus sp. ) in NJ: Smooth (A. serrulata), Speckled / Gray (A. incana, used to be A. rugosa), and European (A. glutinosa)

Alders have woody "cones" for fruit that are generally present all year round. Any tree with cones and broad leaves is generally an alder.

Alders have twice-serrated leaves, that are alternate

Alders have buds that are on stalks (and are alternate)

Alders have long male catkins and very small (smaller than a pencil eraser) female catkins.

Alders live in damp soil near water.

Alders are usually multi-trunked shrubs.


Species (in NJ):

An alder that is a tree, or more than about 20 feet high is European alder.

An alder with blunt-tipped leaves, or especially with any leaves where the tip is indented, is European alder.

An alder in the winter with female catkin cluster clearly drooping below the main branch is speckled alder.

An alder with leaves whose bases are tapered into the stem rather than blunt which also has a taper at the tip end is smooth alder.

An alder with cones upright, not drooping below the stem is smooth alder.

An alder with single teeth (not double toothed) is smooth alder.

An alder with orange hair on veins below is European.


Smooth alder:

Leaves are oval, tapered at both ends, single or double toothed, usually not hairy

Female catkins are upright. Sometimes cones are upright. Sometimes cones droop. Cones have fat and short stems.

Bark is only slightly speckled on twigs, pretty much not speckled on trunks.


Speckled alder:

Leaves are tapered at tip, fairly straight across near stem. Usually very obviously double toothed. Sometimes hairy below.

Female catkins are not upright, either straight out or drooping. Cones have thick, short stems.

Bark nearly always white speckled (short horizontal lines) on twigs and on trunks.

Buds are rounder, fatter than other alders.


European alder:

Leaves blunt or even indented at tip. Not long tapered at tip. Leaves quite wide for length sometimes nearly as wide as long. Sometimes leaf tip indented. Generally very obviously double toothed. Underside of leaf has orange hair on veins. Leaves are shiny above.

Female catkins are upright or straight out from branch, but not obviously drooping. Cones usually dangle. Cones are on long and thin stems.

Bark not generally light speckled on trunks, sometimes dark speckled, sometimes broken into small plates. Bark on twigs can have some speckles but generally not many.