Calcined Clay Improves Germination of Arid Plant Species

Abstract

Water conservation efforts in urban landscapes have increased the need for water-wise-plants. A potential source includes multiple native, drought-adapted species. A lack of researched propagation protocols makes commercial production of many species difficult. We examined germination of three native plant species (Purshia stansburiana, Cercocarpus ledifolius, and Forestiera pubescens) in three substrates. Both P. stansburiana and C. ledifolius are endemic to semiarid areas. Forestiera pubescens is found in riparian areas but is drought hardy once established. Stratified seed of each were sown in substrates varying in organic matter (OM) content and water-holding porosity (WHP) characteristics: (1) a commercial germination mix (83% OM); (2) a self-blended combination of a commercial potting soil mixed volumetrically 1:1 with vermiculite (37% OM); and (3) a calcined clay (0% OM). Germination was monitored for 60 days. Percent germination was highest in the calcined clay for each species evaluated (P. stansburiana: 63%, C. ledifolius: 51% and F. pubescens: 83%). These rates were at least 25% greater than the next best medium, the self-blended substrate. The commercial germination blend was the least favorable for germination. These results suggest that the common commercial practice of using germination substrates may not be suited to germinating many species native to arid areas.