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  • Author or Editor: Jessica D. Lubell-Brand x
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Epimedium is a genus of shade tolerant herbaceous perennials and groundcovers that are slow growing and command high prices. This research examined the influence of division size and timing on propagation success and growth of E. pinnatum ssp. colchicum Boiss., E. × rubrum Morren, E. × versicolor `Sulphureum' Morren and E. × youngianum Fisch. To determine an appropriate division size for each species, small (single bud) and large (three bud) divisions were made in mid-June 2002 and 2003. For the timing study, uniform divisions (three to five buds for E. pinnatum ssp. colchicum and E. × versicolor `Sulphureum'; four to seven buds for E. ×rubrum and E. × youngianum) were made in March, late June and late August, when plants were dormant, had just completed foliage expansion, or were summer dormant. Half of the plants were destructively harvested in the fall and half were overwintered and forced in the greenhouse in early spring. By the end of the growing season, plants grown from large divisions were larger than those grown from small divisions and had produced more buds, however, plants from small divisions produced more buds per initial bud than plants from large divisions, demonstrating a faster increase in growing points. For each species, March divisions produced more vegetative growth, buds, buds per initial bud and potential propagules than June and August divisions, by the end of the growing season. However, by the following spring, both March and June divisions had produced plants of similar size and appearance, while plants grown from August divisions were smaller and of lower quality.

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Genetically female seed is sought for cannabidiol (CBD) hemp production because CBD is extracted from the flowers of female hemp plants. The production of all female seed requires masculinization of female plants to produce genetically female pollen that reliably generates female seed. Of the five female hemp genotypes that we masculinized using foliar sprays of silver thiosulfate (Abacus, Cherry Wine, Mountain Mango, Youngsim10, Wife), all genotypes produced fewer large and more irregular or misshapen pollen grains than genetically male plants. The masculinized female genotypes Wife and Cherry Wine produced pollen with germination rates similar to those of the male genotype Kentucky Sunshine. Female hemp genotypes vary in their ability to produce usable pollen that disperses well, is easily collected, and germinates as well as pollen from genetically male hemp plants.

Open Access

Aroniaberry (Aronia mitschurinii) produces small pome fruits that possess health promoting compounds. Management practices for orchards are lacking, since aroniaberry is a relatively new crop. Pruning is an important cultural practice to optimize fruit yield in orchards. The response of an established aroniaberry orchard to pruning was evaluated over three years (2020 to 2022). Pruning treatments were as follows: 1) renewal pruning (removal of shoots to the base) only in year 1; 2) renewal pruning in year 1 + thinning to 18 shoots in year 2; 3) renewal pruning in year 1 + thinning to 9 shoots in year 2; and 4) no-pruning (control). In response to renewal pruning, plants grew uniformly and vigorously, producing 28 new vegetative primary shoots with an average length of 66 cm by the end of the first growing season. Limited flowering and fruiting occurred in the second season for plants receiving pruning treatments. Fruit yield on pruned plants was significantly less than for unpruned controls. In season 2, increased thinning of renewal-pruned plants negatively affected the number of inflorescences per plant, but positively affected individual fruit fresh weight and fruit °Brix:titratable acidity ratios. Fruits from all treatments had similar monomeric anthocyanins, total phenolics and mineral content. In season 3, flower production and predicted fruit yield from pruned plants and unpruned controls were similar, even though pruned plants were substantially smaller. In the third season, there were no longer any differences between renewed + thinned plants and those that received only renewal pruning, making shoot thinning an unnecessary practice. The results of this study demonstrate that renewal pruning can be an effective way to manage and rejuvenate an aging aroniaberry orchard.

Open Access

To maximize yield, cannabidiol (CBD) hemp producers prefer female plants, and this is accomplished by using expensive feminized seed, vegetatively propagated female clones, or by removing male plants from dioecious seed lots. Hemp pollen drifts long distances on wind, and pollination of females reduces CBD content. Induction of triploidy is a common strategy used by plant breeders to produce sterile cultivars of agricultural crops. Triploid (3n) hemp, with three sets of chromosomes, was developed by crossing naturally diploid (2n) hemp with tetraploid (4n) hemp. Tetraploid plants used to create triploids were produced using pregerminated seeds and the mitotic spindle inhibitor colchicine. Seedlings from seeds of ‘Abacas’ × [(‘Otto2’ × ‘BaOx’) × (‘BaOx’ × ‘Colorado Cherry’)] treated with 0.05% colchicine or 0.02% colchicine for 12 hours and longer were significantly shorter than controls and ≤1 cm tall at 10 days after sowing. Surviving seedlings exhibited thickened cotyledons and hypocotyls, which indicated a potential change in ploidy. Tetraploid induction ranged from 26% to 64% for pregerminated seeds of five different hemp cultivars (Abacus × Wife, Cherry Wine, Mountain Mango, Wife, and Youngsim10) treated with 0.05% colchicine for 12 hours. Tetraploids had nearly twice the DNA content as diploids according to flow cytometric analysis. Tetraploid ‘Wife’ had larger stomates and reduced stomatal density compared with diploid ‘Wife’. Four triploid ‘Wife’ genotypes produced from crossing tetraploid ‘Wife’ with diploid ‘Wife’ were acclimated to greenhouse conditions after embryo rescue. DNA content and stomate size of triploid ‘Wife’ was intermediate between the parents. This is the first report of triploid plants of hemp. Future research will evaluate the sterility of triploid hemp.

Open Access

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.

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Winged euonymus [Euonymus alatus (Thunb.)] is an important landscape shrub that has demonstrated its potential to be invasive in numerous states across the central and northern United States. Nine cultivars were evaluated for their potential to produce fruits and seeds in a randomized, replicated field planting. Seeds from all cultivars were evaluated for germination rate and initial survival in a deciduous woodland. Seeds collected from ‘Compactus’ were also sown in five natural environments (full sun meadow, edge of woods, moist woods, dry woods, pine woods) to determine which habitat types support its germination and establishment. Seed production for cultivars varied from 981 to 6090 seeds per plant. The dry deciduous woods and pine woods were the only environments that supported significant germination rates that could be as high as 37.8%. Seedling survival was at least 77% in the deciduous dry woods and at least 55% in the pine woods. In the first replication, establishment rates for cultivars in the dry deciduous woods ranged from a low of 6.5% for ‘Odom’ Little Moses™ to a high of 42.5% for ‘Monstrosus’. In the second replication, all cultivars achieved over 30% establishment and most exceeded 40% establishment. An estimate of the annual seedling contribution per plant per cultivar was calculated by combining seed production data with establishment data for each cultivar. This estimate was predicted to range from 588 to 3763 and therefore none of the nine cultivars evaluated should be considered non-invasive based on our findings. Our findings show that germination and seedling survival rates are high for E. alatus and because the species is long-lived, cultivars will likely have to be completely seed-sterile to be considered non-invasive according to demographic models.

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Comptonia peregrina is a desirable native ornamental plant for challenging landscapes, but it cannot be produced using conventional softwood stem cuttings. We demonstrate that C. peregrina can be successfully propagated using young shoots (6 to 8 cm in length) recently emerged from rhizomes taken as cuttings. Although significantly more cuttings rooted using intermittent mist (99%) than propagation dome (70%), cuttings under propagation domes had greater shoot counts. Due to the drier and warmer conditions under propagation domes, cutting shoot tips were killed, which relieved apical dominance and stimulated lateral budbreak. Cuttings rooted under propagation domes produced plants having greater height, width, and size after 90 d than cuttings rooted under intermittent mist. Treatment of cuttings with talc-based rooting hormone at 3000 and 8000 ppm indole-3-butyric acid (IBA) significantly improved rooting percentage and shoot count over untreated cuttings. Cuttings treated with 8000 ppm IBA produced the most roots. Container plants grown from cuttings and pruned to 7 cm in height produced twice as many shoots as unpruned plants. Using cuttings taken from young shoots (6 to 8 cm) produced from rhizomes, 3000 or 8000 ppm IBA, and intermittent mist nursery growers can achieve rooting percentages for C. peregrina above the 80% benchmark preferred for commercial plant production.

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Interest in native landscape plants to support pollinators has increased. Most native plants sold by nurseries are cultivars, and some consumer and conservation groups question the suitability of native cultivars to support pollinators. In 2017 and 2018, insect pollinator visitation was quantified for six native shrub species and one or more cultivars of each species (Aronia melanocarpa, A. melanocarpa ‘UCONNAM012’ Ground Hog®, A. melanocarpa ‘UCONNAM165’ Low Scape Mound®, Clethra alnifolia, C. alnifolia ‘Hummingbird’, C. alnifolia ‘Ruby Spice’, Dasiphora fruticosa, D. fruticosa ‘Goldfinger’, D. fruticosa ‘Pink Beauty’, Hydrangea arborescens, H. arborescens ‘Annabelle’, Kalmia latifolia, K. latifolia ‘Sarah’, Physocarpus opulifolius, and P. opulifolius ‘Monlo’ Diabolo®). Insects were identified into 12 categories (Apis mellifera, Bombus spp., Andrenidae, Halictidae, Megachilidae, other bees, Lepidoptera, Syrphidae, other flies, wasps, Coleoptera, and other insects). The number of inflorescences and insect visitation was similar for C. alnifolia and its cultivars, and the compact cultivar Hummingbird had the greatest floral density. A. melanocarpa had more total visitors of Andrenidae than both of its compact cultivars because it was larger and produced more inflorescences. Compact Aronia cultivars and the straight species were mostly similar for Andrenidae visitation when compared on a per-inflorescence basis. D. fruticosa had more visitors of Bombus spp. and Megachilidae than both of its cultivars. These insects may have been less attracted to ‘Pink Beauty’ because of its pink flower color and ‘Goldfinger’ because of its wider flowers, which result from it being a tetraploid. H. arborescens ‘Annabelle’ had one-third the number of Bombus spp. visitors as H. arborescens because ‘Annabelle’ produces >50% fewer fertile florets. P. opulifolius ‘Monlo’ attracted more syrphids than P. opulifolius possibly because flowers contrasted more strongly with the reddish purple foliage of ‘Monlo’ than with the green foliage of the straight species. Insect visitation was similar for K. latifolia and K. latifolia ‘Sarah’. Based on this work, we determined that native shrub cultivars are not universally less or more attractive to pollinators and must be evaluated on a case-by-case basis.

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