Interest in hemp (Cannabis sativa) for its medicinal compounds, cannabidiol (CBD), and Δ-9-tetrahydrocannabidiol (THC), continues to increase. Maximizing yield of CBD and/or THC requires female plants because female inflorescences accumulate significantly greater concentrations of these compounds than male inflorescences. Production of all female seed requires induction of female plants to develop male flowers that produce genetically female pollen. Growers would like access to feminized seed to produce all-female crops. We evaluated the efficacy of 0, 0.3, and 3 mm silver thiosulfate (STS) applied as a foliar spray (on three occasions 7 days apart) to produce male flowers on four strains of female hemp (having a THC concentration of ≤0.3%), designated CBD hemp A, CBD hemp B, CBD hemp C, and industrial hemp. Silver thiosulfate at 3 mm was the most efficacious treatment for all strains. The majority of inflorescences had 100% male flowers at 3 mm STS, and terminal inflorescences had ≥95% conversion to male flowers. Silver thiosulfate at 0.3 mm produced partial conversion to male flowers, whereas most inflorescences had around 50% male flowers, except for CBD hemp A, which demonstrated greater levels of masculinization. At 0.3 mm STS, terminal inflorescences of CBD hemp A had 91% conversion to male flowers. This study demonstrates that male flowers can be produced easily and consistently on female plants through application of foliar sprays of STS under short-day conditions.

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Nursery producers are interested in supplying sedum (Sedum sp.)-vegetated modular units for the green roof industry. This research examined the influence of three rates of controlled-release fertilizer (CRF) (50, 78, and 108 g per unit of 15N–3.9P–10K, 8- to 9-month formulation) on production of modules containing one or two Sedum species. Six Sedum species were evaluated independently: ‘Angelina’ sedum (Sedum rupestre), gray sedum (S. pachyclados), ‘John Creech’ sedum (S. spurium), tasteless sedum (S. sexangulare), ‘Weihenstephaner's Gold’ sedum (S. kamtschaticum var. floriferum), and white sedum (S. album). The species were then paired as follows: white sedum/‘John Creech’ sedum, ‘Weihenstephaner's Gold’ sedum/‘Angelina’ sedum, and gray sedum/tasteless sedum. For each pair, three starting proportions of cuttings were studied. In 8 weeks, the medium and high fertility rates produced significantly more units with at least 95% vegetation coverage than the low rate. In general, increasing the fertility rate increased the fresh weight at time of harvest, except for ‘Weihenstephaner's Gold’ sedum and tasteless sedum at the high rate, which developed “melt out.” Melted-out tissues turned brown, desiccated and detracted from the visual appearance of units. ‘John Creech’ sedum and white sedum had the greatest fresh weight followed by ‘Weihenstephaner's Gold’ sedum, ‘Angelina’ sedum, and tasteless sedum. Gray sedum grew substantially slower than all other species and had the lowest fresh weight. For white sedum/‘John Creech’ sedum units, harvest fresh weight proportions were similar to starting cutting fresh weight proportions. For gray sedum/tasteless sedum units, tasteless sedum outgrew gray sedum and gray sedum was barely noticeable in finished units. Harvest fresh weight and digital image analysis (DIA) of ‘Weihenstephaner's Gold’ sedum/‘Angelina' sedum units indicated that ‘Weihenstephaner's Gold’ sedum colonized units faster than ‘Angelina’ sedum, and had greater visual impact in finished units. Units started with 25% ‘Weihenstephaner's Gold’ sedum cuttings, the smallest proportion tested, were roughly 73% covered with ‘Weihenstephaner's Gold’ sedum at harvest. We recommend growers use the medium fertility rate to produce the most units with 95% vegetation or more in the least amount of time and with reduced risk of melt out. To achieve desired final species proportions, growers may need to adjust the ratios of cuttings based on uneven species vigor.

Japanese barberry is an important landscape shrub that has a demonstrated potential to be invasive in ∼30 states across the central and northern United States. Forty-six cultivars were evaluated for their potential to produce fruits and seeds in a randomized, replicated field planting. Seeds from a subset of cultivars were evaluated for their ability to germinate and survive as seedlings in a deciduous woodland. Seed production for cultivars varied from no seeds to more than 12,000 seeds plant−1 and the number of seeds per fruit ranged from 0.1 to 1.8. Five cultivars produced fewer than 100 seeds plant−1, and two cultivars failed to produce fruit. When plants were allowed to mature for 4 to 5 yr beyond the first evaluation time, cultivars exhibited significant increases in fruits per plant, producing as much as 35,000 fruits plant−1 (‘Sparkle’). ‘Golden Devine’ and ‘Red Chief’, fruitless cultivars at the first evaluation, produced 165 and 20 fruit plant−1, respectively, at the follow-up evaluation, demonstrating that long-term evaluation of cultivars is necessary to accurately assess sterility. Between 12.5 and 31% cultivar seed sown in a deciduous woodland germinated, and seedlings survived at rates between 5.6 and 29.3%. Coupling cultivar seed-production data with germination and survival data in a deciduous woodland suggests that even cultivars producing as few as 100 seeds annually have the potential to contribute a few seedlings each year to a natural area.

While japanese barberry (Berberis thunbergii DC.) is an acknowledged invasive plant naturalized throughout the eastern and northern U.S., the danger posed by its popular horticultural forms is unknown and controversial. This work analyzed the reproductive potential and seedling growth of four ornamental genotypes important to the nursery industry. Fruit and seed production was quantified in 2001, 2002, and 2003 for multiple landscape plants of B.t. var. atropurpurea, `Aurea', `Crimson Pygmy', and `Rose Glow'. The average number of seeds produced per landscape specimen ranged from lows of 75 and 90 for `Aurea' and `Crimson Pygmy' to 2968 for var. atropurpurea and 762 for `Rose Glow'. Seed production relative to canopy surface area for `Rose Glow' was similar to `Aurea' and `Crimson Pygmy' and all three cultivars were less prolific than var. atropurpurea in this regard. Cleaned and stratified seeds from var. atropurpurea, `Crimson Pygmy' and `Rose Glow' showed an average greenhouse germination rate of 70% to 75%, while `Aurea' yielded 46% germination. A subpopulation of seedlings from each genotype accession was grown further outdoors in containers for a full season to ascertain seedling vigor and development. The vigor of 1-year-old seedlings, as measured by dry weight of canopy growth, for progeny derived from `Aurea' (0.70 g) and `Crimson Pygmy' (0.93 g) was significantly less than var. atropurpurea (1.20 g) and `Rose Glow' (1.33 g). These results demonstrate that popular japanese barberry cultivars express disparate reproductive potential that, after further study, may be correlated with invasive potential. Some popular commercial cultivars may pose significantly less ecological risk than others.