Amur corktree

not listed

NNA - Not applicable

not listed

Amur corktree is listed as an invasive terrestrial plant by the Minnesota Department of Natural Resources.

Specially Regulated Plant

In 2023, the Minnesota Department of Agriculture added Amur corktree to the Specially Regulated Plant list.

Only sales of named male cultivars permitted. Sales of all other Phellodendron amurense are prohibited. All existing planted and escaped fruit producing trees must be controlled, by tree removal or other means, such that no seed is disseminated.

When allowed to become established Amur corktree can create dense stands consisting of a large number of small trees that crowd out native species. It produces massive amounts of berry-like fruits which remain on the tree into winter. Seeds are spread by American Robins and other birds.

Amur corktree is a moderate- to fast-growing, 30′ to 45′ tall deciduous tree rising on a single trunk from a wide-spreading root system.

The trunk is short and divided low into several large branches. The crown is broad and often flat topped.

The bark on young trees is light golden brown or yellowish-gray. On mature trees the bark is gray, thick, deeply furrowed, and slightly spongy or corky. Inner bark is bright yellow.

First year twigs are light green to green, hairless, slender, and round in cross section. They have white pith. Second-year twigs are brown, smooth, slender, and shiny, with scattered pale, raised dots (lenticels). Third-year twigs are slender and dull brown. They have tan pith. The leaf scars are large, raised, and U-shaped, almost encircling the bud. They have 3 groups of small bundle scars. The bud is concealed by the leaf stalk (petiole) until the leaf drops. It is brown, naked, broadly rounded, and covered by 2 brown, fuzzy, immature, scale-like leaves.

The leaves are deciduous, opposite, 10″ to 15″ long, and pinnately divided into usually 7 to 11, sometimes 5 or 13, leaflets. The petiole and central leaf axis (rachis) are light green, pale reddish-green, or almost white, and may be hairy or hairless. The rachis is slender.

The leaflets are lance egg-shaped to egg lance-shaped, 2⅜″ to 4¾″ long, and 1″ to 1¾″ wide. They are rounded at the base and taper to a point at the tip with concave sides along the tip. The upper surface is dark green, shiny, and hairless. The lower surface is pale green and either hairless or hairy just along the veins. The margins are untoothed and have a fringe of short hairs. In autumn the leaves turn bright yellow.

Male and female flowers are borne on separate trees. They appear from May to June. The inflorescence is a loose, open and spreading, 2″ to 3″ long cluster at the end of a stem.

Each flower is about ⅛″ in diameter and is borne on a slender stem (pedicel). There are 5 sepals and 5 petals. The sepals are green or maroon, united at the base, and separated into 5 teeth at the tip. The petals are yellowish-green, united at the base, and separated into 5 lobes. Male flowers have 5 stamens with white filaments and bright yellow anthers protruding well beyond the petals. Female flowers have a pistil and 5 rudimentary staminodes that do not project beyond the petals.

The infructescence is loose, open, and spreading. Each fruit is a ¼″ to ½″ in diameter berry-like drupe with 5 seeds. It ripens from mid-June to mid-July. It is green at first, turning black when mature. The fruits remain on the tree until early winter.

30″ to 45″

There is no Minnesota state champion of non-native trees.

Yellowish-green

Moist but well-drained. Full to partial sun, but saplings are highly shade tolerant. Rich soil.

May to June

None

Sources

2, 3, 4, 7, 22, 29, 30.

Native to eastern Asia. Cultivated in Europe and Australia. Introduced in North America around 1856. Naturalized.

Adventive. Rare in Minnesota.