Methods of Tree Seed Treatment by Species
Hickory - This tree nut is generally considered to exhibit embryo dormancy. The common treatment is to stratify the nuts in a moist medium at 33 to 50 degrees F for 30 to 150 days. If cold storage facilities are not available, stratification in a pit with a covering of about 0.5 m of compost, leaves, or soil to prevent freezing will suffice. Prior to any cold stratification, nuts should be soaked in water at room temperature for 2 to 4 days with 1 or 2 water changes each day.
Black Walnut - A walnut is generally considered to exhibit embryo dormancy. The common treatment is to stratify the nuts in a moist medium at 33 to 50 degrees F for two or three months. Although the seed coat is extremely hard it usually cracks, becomes water permiable and does not need scarification.
Pecan - A pecan does not fall into dormancy like other hickories and can be planted at any time with the expectation that the embryo will germinate. Still, the pecan nut is often collected and cold-stored for planting the next spring.
Oak - Acorns of the white oak group generally have little or no dormancy and will germinate almost immediately after falling. These species should usually be planted in the fall. Acorns of the black oak group exhibit variable dormancy and stratification is usually recommended before spring sowing. For best results, moist acorns should be held for 4 to 12 weeks at temperatures of 40 to 50 °F and can be placed in plastic bags without medium if turned frequently.
Persimmon - Natural germination of common persimmon usually occurs in April or May, but 2- to 3-year delays have been observed. The main cause of the delay is a seed covering that causes a major decrease in water absorption. Seed dormancy also needs to be broken by stratification in sand or peat for 60 to 90 days at 3 to 10 °C. Persimmon is hard to artifically germinate.
Sycamore - American sycamore needs no dormancy, and pregermination treatments are usually not required for prompt germination. Germination rate of sycamore can be increased by treating with gibberellin (GA3) at 100 to 1,000 mg/l.
Pine - Seeds of most pines in temperate climates are shed in the autumn and germinate promptly the next spring. Seeds of most pines germinate without treatment, but germination rates and amounts are greatly increased by pretreating the seeds. This means storing seeds, using moist, cold stratification.
Elm - Under natural conditions, elm seeds that ripen in the spring usually germinate in the same growing season. Seeds that ripen in the fall germinate in the following spring. Although seeds of most elm species require no planting treatment, American elm will remain dormant until the second season.
Beech - Beech seeds need to overcome dormancy and requires cold stratification for prompt germination. The seeds may take a combination of stratification and storage. Seed moisture level is the key to successful stratification in beech. Beech is hard to artifically germinate in significant amounts.