Refinement and Stratification of Thinleaf Alder and Water Birch Seeds from New Mexico

Abstract

For multiple seed collections of thinleaf alder (Alnus tenuifolia (Nutt.) Breitung [Betulacae]) and water birch (Betula occidentalis (Hook.) [Betulacae]), response to IDS (Incubation, Drying, and Separation), gravity separation, and stratification was highly variable among seed collections. In thin-leaf alder, drying periods of 18 or 24 h following a 24-h incubation period were comparable to dry seed separation in petroleum ether for increasing percentage of filled seeds. In water birch, IDS treatments resulted in lower percentages of filled seeds than separation in 95% ethanol. Overall, cold (5 °C [41 °F]) wet stratification for 56 d improved water birch germination from 11% to 16%. In thinleaf alder, response to a 56-d stratification ranged from 0% to 16% germination improvement. Using separated seed in combination with appropriate stratification length achieved the largest improvements in germination. Treatment selection is discussed in relation to optimizing use of limited greenhouse space and seed supply.