Six durable but slow-to-establish groundcover species, and three fast-growing but short-lived groundcover species, were planted singly and in paired combinations under mature landscape trees to test for relative weed suppression. Installations were replicated on an urban site and a rural site, monitored for two growing seasons, and weeded periodically by hand. All weeds were dried and weighed, and subplot averages (160 observations) for each plant combination were tested by analysis of variance. Weeds were significantly fewer and smaller in the mixed species than in single species subplots. Weed biomass was also significantly less in monospecific groundcover subplots than in unplanted control plots. These results suggest that reduced maintenance cost (and input) for weed control, along with better initial coverage appeal of the paired plantings, may increase marketability of perennial groundcovers.
Martin F. Quigley and Stephen Mulhall
Goldenseal (Hydrastis canadensis) is an herbaceous perennial valued for its fleshy rhizomes, which contain the alkaloids hydrastine and berberine. While it is understood that relative shade influences growth and yield of goldenseal, optimal shade level for maximum rhizome mass and plant vigor under cultivation has not been established. Goldenseal plants grown from cold stratified rhizomes were kept under shade for 5 months in the greenhouse. Treatments were five different shade levels ranging from 60% to 95% of full shade, plus a control group in full sun. Measured variables included rootlet length, bud development, and rhizome mass. Plants grown under moderate shade (60 to 70%) produced longer and more numerous rootlets, more bud primordia, and had greater rhizome mass and healthier leaves than plants grown under extreme shade (95%) or in full sun. Decreasing shade density had a major impact on plant condition and growth. Those plants grown with the greatest sun exposure displayed 100% scorch damage to the foliage, in comparison to <35% damage in the moderate shade (30 to 40%). The results suggest that moderate shading may double yield in rhizome mass, and promote increased bud proliferation in subsequent seasons. Late season leaf vigor is not correlated with rhizome mass.
Yulia Kuzovkina and Martin F. Quigley
The study addresses the problem of diversification and quality of willow (Salix) cut stems. Very few ornamental willow species are currently in production for the cut-stem trade in temperate North America, and they have a relatively short annual harvest period. This study selected 20 taxa of willow with the potential for cut-stem industry based on observations of more than 150 taxa in central Ohio for 4 years. Growth and ornamental qualities of branches and inflorescences of those species, hybrids, or cultivars were measured and evaluated. The species range in hardiness from USDA zones 2 through 7, but the majority are best suited to zone 4 and 5 conditions. Specific descriptions of each species are provided, focusing on those details important for the floral industry including stem length, bark and bud colors, catkin color and quality, optimal harvest time, and the sequence of bloom among species. Stems for catkin display can be harvested and marketed from January through April. Branches used for bark and bud color displays and for stem shape have an even longer harvest period. New selections provide a greater range of stem size, catkin characteristics, bark and bud color, and prolonged harvest period, than commonly used pussy-willows.
Tina M. Rivera, Martin F. Quigley and Joseph C. Scheerens
The commercial and ornamental potential of three apple-berry polyculture systems was ascertained by monitoring the above-ground performance of component species in plots of `GoldRush' apple (Malus ×domestica Borkh.) trees on M.7 rootstock cropped with either blackberry (Rubus spp. L. `Navaho'), edible honeysuckle (Lonicera caerulea L. `Blue Belle' and `Blue Velvet'), or jostaberry (Ribes nidigrolaria Bauer `Josta') as understory plants. Polyculture plots and corresponding monoculture controls were established in 1999, with berry plants at recommended (R) or close [(C), half-recommended] spacings. Blackberries and jostaberries planted in monoculture at recommended spacings [i.e., control (R) plots] amassed dry weights >1 kg/plant by Fall 2001; the dry weight of edible honeysuckle from comparable plots was slightly >0.3 kg/plant. In 2001, blackberry yield (3.1 kg/plant) and fruit weight (3.4 g) were typical of `Navaho' plantings of similar age, whereas jostaberry was only moderately productive (yield = 286 g/plant; fruit weight = 1.4 g). Edible honeysuckle productivity (yield = 13 g/plant, fruit weight = 0.5 g) was minimal, due to disparate flowering phenology between cultivars. `GoldRush' apple growth and productivity (yield = 25 kg/tree; fruit weight = 158 g) was consistent with values expected for trees of similar age. Blackberry plant dry weights were reduced by 20% to 33% when planted at close spacing, whereas blackberry yields were reduced 35% to 38% when grown in polyculture with apple. Both polyculture and plant spacing significantly reduced jostaberry dry weights (i.e., 12% and 24%, respectively) relative to the control, but neither significantly affected jostaberry yield. Conversely, both close-spaced planting and the presence of an apple tree improved the yield of edible honeysuckle. Apple performance was not affected by the presence of an edible honeysuckle understory, but apple growth factors were reduced in blackberry and jostaberry polycultures by as much as 65%. Apple bloom, fruit set, and yield were also significantly reduced in apple-blackberry and apple-jostaberry plots, with fruit numbers/tree averaging <5 in all except the apple-blackberry (C) treatment. None of the polyculture treatments studied were suitable for profitable fruit production. However, each of the polyculture constituents exhibited unique, beneficial attributes with respect to their use as components within an edible landscape.