Alnus × mayrii
Common Name: alder 
Type: Tree
Family: Betulaceae
Native Range: Korea, China
Zone: 4 to 7
Height: 30.00 to 50.00 feet
Spread: 20.00 to 40.00 feet
Bloom Time: March
Bloom Description: Yellowish-brown (male) Purple (female)
Sun: Full sun to part shade
Water: Medium to wet
Maintenance: Low
Suggested Use: Shade Tree, Rain Garden
Flower: Insignificant
Tolerate: Erosion, Wet Soil

Culture

Best grown in medium to wet soils in full sun to part shade. Tolerates some moderately dry, infertile soils plus occasional flooding. Best in cool climates. Does not perform well south of USDA Zone 7. Propagate by softwood cuttings.

Noteworthy Characteristics

Alnus x mayrii, commonly called alder, is a medium-sized deciduous tree of the birch family that typically matures over time to 30-50' tall with a narrow-oval habit. Parents are Alnus japonica (Japanese alder) and Alnus hirsuta (Manchurian alder). This tree is a naturally occurring hybrid cross which occurs in certain areas of Japan and Manchuria where the growth of its parents coincide. Glossy, finely serrate, ovate-lanceolate, dark green leaves (to 3-4” long) are pale green beneath. No appreciable fall color. Flowers are monoecious, appearing in separate male and female catkins (catkins are aggregates of individual flowers in a single structure). Pendant male catkins in clusters with yellowish-brown flowers and short erect less conspicuous female catkins with purplish flowers bloom in late winter to early spring (March). Female catkins are followed by persistent ellipsoidal fruiting cones (to 1” long) with winged seeds which when ripe are dispursed by wind and water. Fruiting cones somewhat resemble the small true cones of some conifers. This hybrid is most similar to its Alnus japonica parent, except its leaves are broader with acute (not acuminate) tips, and it typically grows more vigorously.

Problems

No serious insect or disease problems. Leaf curl, powdery mildew, rust and canker are potential disease problems. Aphids, flea beetles, mealybugs, psyllids and lace bugs are potential insect problems.

Garden Uses

Uncommon in the U.S. Good selection for difficult sites such as moist low spots or dry sites with poor soils. Shade tree. Woodland areas.