Based on experiments by the University of California – Davis, Californian native plant growers can produce high-quality upland native plants by selecting nursery media for container production with as low as 10% air space. As a matter of fact, media at 10% air space reduces production water stress and can give plants a slight boost when they’re planted out, since media will hold more water than surrounding landscape or restoration soils after irrigating.
“One of the main drivers for doing this study was to answer some of the key questions about challenges of producing sufficient [quantities] of good quality native plants,” said Juliet Braslow. Natives can be grown using industry-standard materials. “It’s important to show that many of the plants assumed to be ‘difficult’ to produce don’t require any special media mixes.”
Anecdotally some nurserymen have complained that natives seem to require media with higher aeration than typical and that natives are “difficult to grow.” But based on Juliet’s study of 15 species in typical nursery media and high-porosity media, there were “no consistent observable differences among treatments.”
- Arctostaphylos densiflora Howard McMinn (Vine hill manzanita)
- Arctostaphylos pajaroensis Paradise (Pajaro manzanita)
- Artemesia californica (California sagebrush)
- Aster chilensis (California aster)
- Ceanothus Dark Star
- Cornus nuttallii (Mountain dogwood)
- Dudleya sp. Caespitosa (Sea lettuce)
- Elymus glaucus (Blue wild rye)
- Eriophyllum staechadifolium (Lizard tailor Wooly sunflower)
- Heteromeles arbutifolia (Toyon)
- Lupinus albifrons (Silver bush lupine)
- Mimulus bifidus (Sticky monkey flower)
- Monardella villosa (Coyote mint)
- Penstemon azureus (Azure penstemon)
- Stipa pulchra (Purple needle grass)
Since media didn’t seem to be a limiting factor, did liner quality affect production? Juliet responded saying that she purposely sought uniformly sized liners.
“I acquired more liners than I required just for that reason, to select those that were the most similar in size and quality to test. I did have some qualitative observations about overall growth and flowering, but didn’t notice any significant differences within species or between media or irrigation treatments.”
Upland native species performed well in normal 10% air porosity nursery media. And they didn’t require special irrigation either. Production issues some nurseries experience could be due to other factors besides air porosity, she concluded.
Improving nursery production of 15 California native plant species: the effect of air filled porosity by Juliet Braslow, International Center for Tropical Agriculture (CIAT) Kenya, and Richard Evans, University of California, in Native Plants (Vol. 16 No. 3) Fall 2015. doi: 10.3368/npj.16.3.249
NewTerrain June 1, 2016.