Establishment of Piper’s daisy (Erigeron piperianus) in the shrub-steppe of south-central Washington

Abstract

We studied protocols to enhance introduction of Erigeron piperianus Cronquist (Piper’s daisy [Asteraceae]) to a habitat similar to that of other existing populations in the shrub-steppe of south-central Washington. Seed from a population of E. piperianus growing within 4 km (2.5 mi) of the introduction site was used to propagate seedlings in a greenhouse. Germination was 50 ± 8%. We evaluated the effects of planting density and cover of existing vegetation on plant establishment and survival. Ultimately, seed production and recruitment were assessed. Density of outplanted E. piperianus seedlings had minimal effect on survival. Interference by perennial bunchgrasses reduced survival during the first year of growth. Interference by Salsola kali L. (Russian thistle [Chenopodiaceae]) significantly reduced populations in the second growing season. By spring of the second growing season, survivorship had dropped to 21% but summer seed production occurred on 99% of the remaining plants, resulting in 121 new plants in the summer of the third growing season. Two unplanned events allowed observation of natural impacts on seedling reintroduction. First, outplanting seedlings in late winter resulted in significant losses associated with a severe freeze. Establishment of plantings after the freeze was more successful. Second, severe insect herbivory was evident during the first growing season but appeared to have no impact on plant survival.