White Oak

Site and soil

Choose the spot carefully, because this is not a tree you will move later. NC State Extension describes white oak as preferring deep, moist, well-drained, slightly acidic loam while adapting to other soil types, and fairly drought tolerant once established. Wet sites should be avoided. Ours are grown from regional seed sources for Appalachian conditions and are hardy from USDA zone 3 through zone 9.

• Full sun to partial shade. NC State Extension rates it for six or more hours of direct sun, or two to six hours of direct sun in partial shade.
• Dry to moist ground that drains. Skip low places that hold water.
• Mature size is 50 to 80 feet tall and 50 to 80 feet wide. Plan on about 50 feet between trees and the same kind of distance from buildings, drives, septic lines and overhead wires.
• Protect the root zone. NC State Extension lists white oak as sensitive to soil compaction, so keep vehicles, equipment and heavy traffic off the ground under the canopy.

In a food forest this is the canopy layer. Whatever you plant beneath it should be chosen for the shade that is coming, not the sun that is there now.

Planting

White oak sends a deep taproot down early, and NC State Extension notes that the taproot makes the tree difficult to transplant. The working rule is to plant it young, plant it once, and disturb the roots as little as possible. Have the hole ready before the tree leaves its shade, and keep the roots moist and covered until they are in the ground.

WVU Extension's guidance for planting trees:

1. Dig the hole no deeper than the root ball, so the root flare sits level with the surrounding soil surface.
2. Backfill with the original soil mixed with 20 to 30 percent compost or aged wood chips.
3. Water as you backfill to settle the soil and clear air pockets.
4. Mulch 3 to 4 inches deep over the root zone, pulled back about 2 inches from the trunk so the bark stays dry.

If deer or squirrels work your ground, protect the tree at planting rather than after the damage. Mississippi State Extension recommends fences, tree shelters and seedling sleeves to prevent animal damage to young oaks.

First-year care

Water is most of the job in year one. Penn State Extension's schedule for a newly planted tree is daily for the first week or two, every two to three days through about week twelve, then weekly until the first frost.

• Give at least 1 to 1.5 gallons per inch of trunk diameter, spread over the whole root zone instead of poured at the trunk.
• Skip a watering only after an inch or more of rain.
• Check the soil 6 to 9 inches down with a probe or your finger before you water, rather than watering on a calendar alone.
• Keep the mulched circle weed-free and keep the mulch off the trunk.

Expect a quiet first season above ground. A young oak spends its first year putting roots down, and top growth follows once the root system is established.

Pruning

Prune oaks in the dormant season. University of Minnesota Extension recommends November through February, when the fungal pathogens and insect vectors are inactive, and names April through July as the high-risk window: fresh wounds attract sap beetles that can carry oak wilt spores from tree to tree. White oak is the more resilient group, with the disease progressing slowly over two to five years or longer compared with as little as four weeks in red oaks, but the timing rule is worth keeping anyway.

If a limb tears out in the risky months, University of Minnesota Extension says to treat the cut surface immediately with water-based paint or shellac so the beetles are shut out.

A young white oak needs very little. Take out broken, dead and crossing limbs, settle on one leader if two are competing, and otherwise leave it alone. An open-grown canopy tree does not need shaping, and every cut is a wound you have to time.

Harvest

Acorns ripen and drop in September and October of the same year the tree flowers. Bloom is mid to late spring, April into May as the leaves emerge: white oak is monoecious, carrying male catkins and small female flowers on the same tree, and the wind does the pollinating. It is not strictly self-incompatible, so a single tree can set acorns, but nut set is better with several trees nearby. Crops are masting, with heavy years every four to ten years and light years between. Open-grown trees typically begin bearing at 20 to 30 years, with good crops at 50 and up. Forest-grown trees take longer.

Collecting acorns to grow more oaks

White oak acorns germinate in the fall, with no dormancy to break, so timing matters more here than with most seed.

• Let them fall. Mississippi State Extension says not to pick acorns from the tree, because those are immature, and to collect promptly after the drop. In hot, dry weather it may take as few as 3 to 4 days to kill the seed.
• Keep what you gather cool and shaded so it does not dry out or overheat, and collect two to three times more than you need.
• Float test before planting. Iowa State Extension says sound acorns sink and most floating acorns are not viable, so discard the floaters.
• Sow in fall, half an inch to an inch deep. Iowa State Extension notes white oak acorns germinate immediately after sowing and need no stratification.
• If you would rather sow in spring, Mississippi State Extension says to store white oak acorns at 34 to 40 degrees F in cool, moist sand for no longer than 3 to 4 months.
• Cover your seed spots. Squirrels will dig acorns up, and Mississippi State Extension flags both squirrel populations and deer browsing as reasons seedlings fail.

Most of the crop was never yours. A mature white oak in a masting year feeds the whole hillside, and that is a reasonable thing to plant a tree for.