Tissue culture using mature-phase plant material is a useful tool for species conservation, but can be a challenge with oak (Quercus) species, often resulting in low growth and survival. Two different tissue culture media were compared and used to determine whether there was a survival, growth, or contamination response pattern in species representing three North American oak taxonomic sections: red oaks (section Lobatae), white oaks (section Quercus), and golden oaks (section Protobalanus). Mature phase cuttings were harvested in springtime from 12 oak species: arkansas oak (Q. arkansana), canby oak (Q. canbyi), slender oak (Q. graciliformis), nuttall oak (Q. texana), boynton sand post oak (Q. boyntonii), california scrub oak (Q. dumosa), engelmann oak (Q. engelmannii), gambel oak (Q. gambelii), canyon live oak (Q. chrysolepis), palmer oak (Q. palmeri), island oak (Q. tomentella), and huckleberry oak (Q. vacciniifolia). Excised shoot-tip explants were placed onto either Lloyd and McCown woody plant (WP) medium or Gresshoff and Doy (GD) medium. More growth responses and longer survival times were seen on explants grown on the WP medium than GD medium. Explants originating from species native to xeric habitats or those with smooth, glabrous young leaves had significantly higher contamination rates. Although no significant differences were found when grouped by taxonomic section, survival, growth, and contamination varied significantly by species. These findings contribute to the process of establishing tissue culture methods using mature oak material, particularly in relation to medium selection and sterilization protocols, which is critical to the conservation of this iconic group of species.
Landscape plant evaluations were conducted in eight states: Colorado, Minnesota, North Carolina, Ohio, Oregon, Pennsylvania, Texas, and Vermont for 17 switchgrass (Panicum virgatum) and five little bluestem (Schizachyrium scoparium) cultivars. Additional locations in Florida (Fort Lauderdale, Fort Pierce, Quincy, and Wimauma), Nebraska (Lincoln), and Lubbock and San Marcos completed 1 or 2 years of the trials. Plants were established in 2012 and data were collected for 3 years, 2013–15. Sites were asked to compile annual data on plant height, width, flowering time, fall color, pests, foliage color determined by the Royal Horticultural Society’s color chart, plant form, flowering date, floral impact, self-seeding, winter injury, landscape impact, and mortality. Texas A&M Agricultural Research and Extension Center (Overton), Florida (all four locations), and Vermont had the highest mortality rate. Southern Florida locations lost 50% of their plants by the end of 2014. Wide variation was reported for landscape impact, individual cultivar height, and width from different regions of the United States. Three of the 17 switchgrass cultivars, Cloud 9, Northwind, and Thundercloud, had a rating of 4.0 or higher averaged over six or more locations for plant form, floral, and landscape impact. ‘Shenandoah’ and ‘Warrior’ switchgrass had a rating of 4.0 or higher averaged over six or more locations for plant form and landscape impact, but not floral impact. Only one of the five little bluestem cultivars, Blue Heaven® rated 4.0 or higher, for plant form and landscape impact when averaged over six or more locations. This range of variability in landscape plant performance demonstrates the importance of local plant evaluations.