Improving nursery production of fifteen California native plant species: the effect of air-filled porosity

Abstract

Many studies have shown the importance of air-filled porosity (V_A) for optimal growth and dry weight of container-grown plants, but few have examined its effects on California native plants. Anecdotal evidence suggests that various upland native species require higher substrate aeration or less frequent irrigation than do standard nursery crops. We tested effects of V_A and irrigation frequency on 15 California native species that had been identified by growers as challenging because of their aeration needs and sensitivity to overwatering. Plants were grown in substrates with 10% or 22% V_A and were irrigated once (up to 574 ml) or twice daily (up to total of 972 ml). None of the applied treatments preferentially influenced plant survival or growth. Results indicate that these species may tolerate both normal and high V_A values. The high survival and growth rates in these experiments indicate that growers’ experiences of plant death or poor plant growth are attributable to something other than V_A.