Little Walnut

Size, growth and what to expect

Little walnut grows at a moderate rate, about a foot and a half a year in our growth estimator, and young trees grow fast once rooted. Most trees reach 20 to 30 feet tall and as wide, often with several trunks and low, spreading branches, and trees to 50 feet are known.

Seedling trees first bear at 15 to 20 years, with crops at irregular intervals. It flowers from March to May, and the nuts ripen from August to October. The nut, ½ to ¾ inch across, has a thick, deeply grooved shell around a small, sweet, oily kernel, inside a husk that does not split. Squirrels and other rodents eat the nuts, and the tree is a larval host of the banded hairstreak butterfly.

It grows wild from southwestern Kansas through western Oklahoma and Texas to New Mexico and northeastern Mexico. Its home is rocky creek beds, canyons and dry washes, often under limestone walls, where the narrow woods it forms shelter many birds. NatureServe ranks it imperiled in Kansas, at the northern edge of its range.

How to grow Little Walnut

Little walnut wants full sun or part shade. Give it a well-drained soil, rocky, sandy or loamy. It does well on alkaline ground over limestone. Once rooted it takes heat and drought, but ground that floods from time to time brings root and crown rot. Set trees 20 feet apart, and keep each one 15 feet from a wall and at least 15 feet from overhead wires.

Saplings ship bare-root or potted. Plant a dormant sapling from leaf fall until bud swell, in a hole deep enough for the taproot to hang straight. Set the root flare at the soil line, put the native soil back in, and keep the mulch clear of the trunk. Sow nuts in fall one to two inches deep under hardware cloth, or squirrels dig them up. For spring, hold them damp in the refrigerator for 90 to 120 days first. Never let the nuts dry out, or they will not grow.

Water every week or two through the first summer when rain is short. Cage young trees against deer and rabbits until they are established. Prune only to shape it.

Male and female flowers grow on the same tree but ripen at different times, which favors cross-pollination, so a second little walnut nearby helps. The walnut husk fly spoils ripening nuts after late summer rains, less so on open, windy sites. Little walnut resists walnut anthracnose better than black walnut does. Fall webworms can be a nuisance.