Four herbaceous perennials Aquilegia caerulea `McKana's Giant', Gaillardia aristata, Gypsophila paniculata `Fairy's Pink', and Callirhoe involucrata were subjected to increasing levels of drought stress and evaluated for ornamental quality and performance in the landscape. Drought stress was imposed by irrigation treatments of 100%, 75%, 50%, 25%, and 0% of reference evapotranspiration (ET0) in 1994. Irrigation treatments resulted in Aquilegia exhibiting a decline in plant growth and appearance below the 50% ET0 treatment. Callirhoe grown at the 100% ET0 irrigation treatment were larger than the plants in any other treatment. Gaillardia receiving some irrigation (25% to 100% ET0) were generally larger than those that received no supplemental irrigation (0% ET0). A decline in plant appearance and growth was observed with Gypsophila with lowering irrigation treatments.
David Hillock and James E. Klett
James E. Klett and David Hillock
Herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control and phytotoxicity. During the 1994 season, seven preemergent herbicides, napropamide (Devrinol) at 4.5 and 9.1 kg·ha–1, metolachlor (Pennant) at 4.5 and 9.1 kg·ha–1, isoxaben (Gallery) at 1.1 and 2.3 kg·ha–1, oxadiazon (Ronstar) at 4.5 and 9.1 kg·ha–1, oxyfluorfen + oryzalin (Rout) at 3.4 and 13.6 kg·ha–1, oryzalin (Surflan) at 2.8 and 4.5 kg·ha–1, and trifluralin (Treflan) at 4.5 and 9.1 kg·ha–1, were tested on Aquilegia caerulea `McKana's Giant', Digitalis purpurea, Gaillardia aristata, Limonium latifolium, and Veronica spicata. Isoxaben (both rates) resulted in visual phytotoxicity symptoms and death to Digitalis. Metolachlor (both rates) resulted in plant death to Veronica. Pennant (both rates), when applied to Limonium, resulted in stunted growth. Aquilegia and Gaillardia were not adversely affected. Most herbicides controlled both dicot and monocot weeds effectively.
David Staats, David Hillock, and James E. Klett
Five preemergence herbicides were applied to seven herbaceous perennials to evaluate weed control efficacy and phytotoxicity. Different species were used each year. The species used during 1992 were coneflower (Rudbeckia fulgida Ait. `Goldstrum'), common foxglove (Digitalis purpurea L. `Excelsior'), Shasta daisy (Leucanthemum ×superbum Bergmans `Alaska'), Stokes's aster (Stokesia laevis Greene `Blue Danube'), and avens (Geum Quellyon Sweet `Mrs. Bradshaw'). The species used in 1993 were woolly yarrow (Achillea tomentosa L.) and woolly thyme (Thymus pseudolanuginosus Ronn.). The herbicides and rates were napropamide (Devrinol 10G) at 4 and 8 lb a.i./acre; metolachlor (Pennant 5G) at 4 and 8 lb a.i./acre; oxyfluorfen+oryzalin (Rout 3G) at 3 and 12 lb a.i./acre; trifluralin (Treflan 5G) at 4 and 8 lb a.i./acre; and oxadiazon (Ronstar 2G) at 4 and 8 lb a.i./acre. Plants were grown in no. 1 containers and weed seeds were sown onto the substrate surface. Two control treatments, no herbicides but with weeds (weedy control), and no weeds or herbicides (weed-free control) also were evaluated. Weed control was effective and similar for all herbicides tested. Napropamide at 8 lb a.i./acre caused stunting in foxglove (20% to 45% less growth compared to weed-free control). Oxyfluorfen + oryzlain at 12 lb a.i./acre caused severe phytotoxicity (≈80% to 95% of plant injured) and stunted the growth (70% to 80% less growth, sometimes plant death) of woolly yarrow. Woolly thyme was stunted by all herbicides when applied at the recommended rates (42% to 97% less growth compared to control) except for oxadiazon and oxyfluorfen + oryzlain. Woolly thyme appeared to be more susceptible to phytotoxicity due to its less-vigorous growth habit and shallow, adventitious roots that were in contact with the herbicide.
James E. Klett, David Staats, and David Hillock
During the 1992 season six preemergent herbicides (Devrinol) at 4.5 and 9.1 kg/ha, Metolachlor (Pennant) at 4.5 and 9.1 kg/ha, Isoxaben (Gallery) at 1.1 and 2.3 kg/ha, Oxyfluorfen + Oryzalin (Rout) at 3.4 and 13.6 kg/ha, Oryzalin (Surflan) at 2.8 and 4.5 kg/ha and Trifluralin (Treflan) at 4.5 and 9.1 kg/ha, were tested on Rudbeckia fulgida “Goldstrum”, Digitalis purpurea “Excelsior”, Chrysanthemum maximum “Alaska”, Stokesia laevis “Blue Danube”, and Geum hybrids “Mrs. Bradshaw”. Gallery at both rates resulted in visual phytotoxicity on Chrysanthemum, Digitalis and stunting in Rudbeckia at the 2.3 kg/ha rate. During the 1993 season the same herbicides plus Oxadiazon (Ronstar) at 4.5 and 9.1 kg/ha, were tested on Achillea tomentosa, and Thymus pseudolanuginosus. Gallery and Pennent at both rates resulted in visual phytotoxicity and stunted growth on Thymus pseudolanuginosus. Rout at the 13.6 kg/ha rate resulted in visual phytotoxicity on Achilles tomentosa.
James E. Klett, David Hillock, and David Staats
Herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. During the 1995 season six preemergent herbicides [(in kg·ha–1) Napropamide (Devrinol 10G), 4.5 and 9.1; Isoxaben (Gallery 75DF), 1.1 and 2.3; Oxadiazon (Ronstar 2G), 4.5 and 9.1; Oxyfluorfen + Oryzalin (Rout 3G), 3.4 and 13.6; Oryzalin (Surflan AS), 2.8 and 4.5; and Trifluralin (Treflan 5G) 4.5 and 9.1, were tested on Callirhoe involucrata, Delosperma nubigenum, Dendranthemum ×morifolium `Jennifer', Festuca cinerea `Sea Urchin', and Gypsophila paniculata `Fairy's Pink'. Isoxaben (both rates) resulted in visual phytotoxicity symptoms and sometimes death to Dendranthemum. Oxadiazon (9.1 kg·ha–1) and Oxyfluorfen + Oryzalin (both rates) resulted in plant chlorosis and necrosis to Delosperma soon after herbicide application, but plants outgrew herbicide damage. Napropamide (both rates), applied to Delosperma, resulted in less dry weight when compared to some of the other herbicide treatments. Oryzalin (4.5 kg·ha–1) resulted in visual phytotoxicity and less plant dry weight to Festuca. Data analysis revealed no significant differences in Callirhoe and Gypsophila. In general, most herbicides controlled weeds effectively.
David Hillock, Matthew Kirkwood, Douglas Needham, and Brenda Sanders
The purpose of a service/learning project is two-fold: to gain skill in one's area of study and simultaneously to provide service to an unrelated community. This project provided such an educational opportunity for our Horticulture and Landscape Architecture students by providing the mechanism for them to develop and practice their skills of garden design, presentation, installation, and maintenance, while also providing a service to Oklahoma's fifth grade teachers and their students. Through their service, our students gained insight into the creation of public gardens, specifically ones for children. This project created a template through which elementary educators could then work with their communities to develop children's gardens at their schools. Our students presented gardening ideas via slides to fifth grade classes, geographically distributed throughout Oklahoma, and then surveyed them for their input into a garden designed for and by children. The survey accessed the needs and dreams of both the fifth grade students and their teachers. The children's and teachers' desires, as expressed in the surveys, were incorporated into garden designs by our students. A prototype of one of the children's gardens was then installed at the Oklahoma Gardening studio grounds with the help of Horticulture and Landscape Architecture students, OBGA Ambassadors (a group of horticulturally trained volunteers from the Greater Stillwater Community), and Oklahoma elementary school teachers, who sought to gain experience in garden installation in order to create a children's garden at their own schools. The processes, from conception through design and installation, and finally utilization for elementary education, were videotaped and incorporated into a “how-to” video and fact sheet, produced and made available through the Oklahoma Cooperative Extension Service (OCES).