Germination of seeds of Tamarix ramosissima

Abstract

The germination of seeds of saltcedar (Tamarix ramosissima Ledeb.) was compared at a wide range of constant or alternating temperatures from 0 through 40 degrees C. Germination temperature profiles were developed for seeds of saltcedar collected from the Walker River Delta in western Nevada over a 3 year period. Germination occurred over a wide range of temperatures. For 2 of the 3 years of testing, maximum germination observed was 98 or 100%, indicating the seed lots were highly viable. Germination ranged from 0 to 6% at very cold seedbed temperatures, but jumped to 39 to 43% at cold seedbed temperatures. There was very little difference in germination between moderate and warmer seedbed temperatures. No single temperature always supported optimum germination. The temperatures that most frequently supported optima were 10/20 (10 degrees C for 16 hours and 20 degrees C for 8 hours in each 24 hour period), 10/25, 15/20, and 35 degrees C. Mid summer collections of saltcedar seeds were much more variable in germination response compared to annually repeated late spring collections from the Walker River Delta. Available soil moisture apparently is an important factor in the germinability of saltcedar seeds collected in mid summer. Temperature regimes that supported optimum germination for the Walker River Delta accession of seed collected in mid summer, tended to occur at higher temperatures than for seeds collected from the same stand in late spring. Comparison of the saltcedar profile with germination temperature profiles of seeds of tree willow (Salix lutea Nutt.), coyote willow (S. exigua Nutt.), or Fremont cottonwood (Populus fremontii S. Watson) revealed that germination of saltcedar seeds was equal in the number of regimes with some germination, mean of optima, and maximum observed germination. For all other germination characteristics measured, saltcedar is lower and sometimes distinctly lower than for seeds of the native woody species.