Cleaning

As soon as possible after collection, all acorns should be immersed in water. This procedure serves two functions. First, it allows removal of leaves, cups, other trash, and insect-damaged acorns that float. Sound, healthy acorns typically sink in water. The exception to this rule is overcup oak, whose acorns always float with their large cups full of air spaces. Second, immersion helps maintain that all-important high seed moisture. (Bonner, 1993)

If conditions are extremely dry when acorns are collected from the ground, many good acorns will float initially. Under such conditions, acorns should be kept in the water for up to 24 hours to elevate their moisture contents and allow sound acorns to sink. Acorns collected from wet conditions should separate easily at initial floating. One should always cut samples of "floaters" and "sinkers" to determine the effectiveness of flotation to remove bad acorns. (Bonner, 1993)

After flotation and removal of trash, the water should be drained away prior to storage. Insect control measures should be taken at this time. The two common methods of control are immersion in hot water (120?F) for 40 minutes, and fumigation with methyl bromide or other recommended chemicals (Olson 1974). Both of these methods present considerable risk to acorns, and the best alternative may be to do nothing. Most infested acorns will be removed in flotation. The larvae do not attack intact acorns during storage, so infestation does not increase. Damage is further decreased when acorns are put into cold storage. The temperature change encourages larvae to emerge from the acorns to pupate, and they die in the bottom of the container. Additional larval emergence can be encouraged by moving the acorns from cold storage to room temperatures and back again. Larval feeding must destroy the embryonic axis to prevent germination, so damage solely to cotyledon tissue does not prevent germination and development of a normal seedling. (Bonner, 1993)

If acorns are to be sized, the separations should be done at this time. Most nurserymen do not size acorns, but increasing use of mechanical planting, both in nurseries and in direct seeding, may lead to a wider adoption of the practice. Round-hole screens that are used in air-screen cleaners may be used, especially for small acorns. Sizing can have advantages in nurseries through its effect on seedling uniformity. A positive correlation between acorn size and seedling size (height or leaf area) has been reported for (Q. rubra L.) (Farmer 1980), Q. robur L., and Q. petraea (Mattushka) Lieblein. (Kleinschmit and Svalba 1979). (Bonner, 1993)