Fraxinus latifolia

Oregon Ash
Oleaceae
Deciduous, Trees

FRAXINUS

Fairly fast-growing trees, most of which tolerate hot summers, cold winters, and many kinds of soil, including alkaline sorts. Chiefly used as street, shade, lawn, and patio shelter trees. In most cases, leaves are divided into leaflets. Male and female flowers (generally inconspicuous, in clusters) grow on separate trees in some species, on the same tree in ­others. In the latter case, flowers are often followed by clusters of single-seeded, winged fruit, often in such abundance that they can be a litter problem. When flowers are on separate trees, you’ll get fruit on female tree only if a male tree grows nearby.

Ash trees are prone to borers. In some parts of California, ash whitefly is a problem; these chalky white, 1/8-in.-long insects colonize in patches on leaf undersides. Outbreaks are usually controlled by natural enemies; avoid spraying with broad-spectrum insecticides, which are likely to wipe out these beneficial predators.

Fraxinus latifolia

Native to Sierra Nevada and west of the Cascades from Northern California to Bri­tish Columbia. To 40 to 80 ft. tall, 30 to 50 ft. wide. Leaves 6 to 12 in. long, divided into five to seven oblong to oval, light green, hairy or smooth leaflets; end leaflet to 4 in. long, larger than side leaflets. Male and female flowers on separate trees. Will grow in standing water during winter months. Needs no dry-season irrigation. Subject to many pests and diseases; not a first-rate tree.