Photo: Mason Brock, Public domain · Wikimedia Commons

Blackjack Oak

Quercus marilandica

Also called jack oak, barren oak.

A tough red oak for poor, dry sand and clay, with leathery, bell-shaped leaves and near-black bark broken into blocks like alligator hide.

RareDrought tolerantWildlife value

Type: Small tree
Mature height: 20–40 ft
USDA zones: 6–9
Growth rate: Slow
Sun: Full
Soil moisture: Dry, Average
Grows wild in: Dry uplands, sandy barrens and rocky ground
Native range: 26 states and the District of Columbia, north to New York, south to Florida and west to Nebraska
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Alabama, Arkansas, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, Nebraska, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, West Virginia and the District of Columbia
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Blackjack oak is a red oak of dry ridges, barrens and sandhills, common across the East and South on ground too poor for most trees. With post oak it forms the Cross Timbers, the band of small oaks where forest gives way to prairie in Oklahoma and Texas. It is rarely planted, and it is best in naturalized or woodland settings. Given good soil and room, it grows a full, symmetrical crown. Plant it on a dry bank, a thin-soiled slope or a sandy corner where other trees have failed.

Size, growth and what to expect

Blackjack oak seedlings in Missouri averaged under 2 inches of height a year over six years. That is far below the foot a year our growth estimator gives a slow tree. Expect a compact 20 to 40 feet, with a crown as wide. On poor, dry ground the same record keeps it under 30 feet, and better sites grow it to 45 or 50.

It flowers from March to May, and the acorns ripen from September to November of their second season. It bears younger than many oaks, and on burned ground sprouts only 3 or 4 years old have borne acorns. The acorns are half an inch to an inch long, in a deep cup with loose scales, and jays, turkeys, squirrels and deer eat them.

It grows wild from Long Island to northwest Florida and west to central Texas and eastern Kansas. It keeps to dry, poor sand, gravel or clay, and after a fire it sprouts from the root crown.

How to grow Blackjack Oak

Blackjack oak wants full sun and a dry, well-drained soil, acid and poor if need be. It will not grow in shade, and wet, poorly drained ground often kills young trees. Set trees 20 feet apart, and keep each one 20 feet from a wall and at least 15 feet from overhead wires.

Saplings ship potted. Blackjack oak moves badly unless its roots are trained while it is young, so plant it once. Plant from leaf fall until bud swell, in a hole wider than the pot and no deeper. Set the root flare at the soil line, put the native soil back in, and keep the mulch clear of the trunk. Red oak acorns need a winter before they sprout. Sow them in fall an inch deep under hardware cloth. For spring, hold them damp in the refrigerator for 60 to 90 days first.

Water every week or two through the first summer, then only in a long drought. Deer and rabbits browse young oaks, so guard each sapling with a tube or cage for its first three years. Dead lower branches tend to hang on for years, and you can cut them off in the dormant season.

The flowers are wind pollinated, and an acorn crop wants another oak nearby. As a red oak it can catch oak wilt, so prune only in the dormant season, to avoid the beetles that spread it. The two-lined chestnut borer and a canker fungus have been found on dying trees. In the wild it crosses with many red oaks, among them Georgia oak, bear oak and shingle oak.

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

Sources (10)