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  • Author or Editor: Curtis Jones x
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Green roofs provide multiple environmental and economic benefits, such as roof surface temperature reduction, reduced internal cooling needs, storm water management, and extended life span of roofing materials. However, green roof substrates must be relatively lightweight, so it is typically coarse with limited water holding capacity. We hypothesize the physical characteristics that make the substrates successful on a roof are likely to reduce seed germination. For this study, we tested the germination of three perennial species and one annual: shasta daisy (Leucanthemum ×superbum), yarrow (Achillea millefolium), and indian blanket (Gaillardia pulchella), and pinto bean (Phaseolus vulgaris) (as a control) across five different substrates: peat/perlite/large expanded shale, compost/sand/expanded shale, compost/black dirt/expanded shale, compost/expanded shale, and peat/perlite (control). Substrate physical and chemical properties were analyzed, and a germination test conducted using a randomized complete block design, with each species/substrate combination appearing once per block. Germination was defined as seedling emergence, and monitored every 7 days for 28 days. Pinto bean had the highest germination (76.2%) across all substrates, compared with 43.4% for indian blanket, 40.4% for yarrow, and 23.0% for shasta daisy. Seed germination, across all species, was lower in green roof substrates. Germination success was very strongly correlated with seed length, seed width, and seed area, while no relationship was found between seed germination and substrate pH or electrical conductivity (EC). Therefore, it is likely that the physical characteristics of green roof substrates create poor conditions for seed germination.

Free access

The Ebony series of crepe myrtle (Lagerstroemia indica) cultivars includes several (Ebony Embers, Ebony Fire, Ebony Flame, Ebony Glow, and Ebony and Ivory), marketed today under the Black Diamond® brand. These are relatively new crepe myrtle cultivars unique for their dark foliage, but with little information concerning their performance in north-central Texas, especially in low-input landscapes. The study was conducted from 2014 to 2017 at three locations in north-central Texas with three soil types, an acidic fine sandy loam, a neutral pH silt loam, and an alkaline heavy clay. Although soils and environmental conditions caused variations between sites, overall performance among cultivars was consistent across all study sites, with Centennial Spirit having better landscape performance than any of the Ebony cultivars tested. ‘Ebony and Ivory’ and ‘Ebony Blush’ had the overall lowest landscape performance. Ebony cultivars grew more slowly, had fewer blooms, and were more susceptible to powdery mildew than Centennial Spirit. While the trees may perform better in more intensively managed landscapes, the Ebony cultivars did not perform as well as Centennial Spirit in low-input landscapes in north-central Texas.

Open Access