In June 1991, a two year field study was initiated to examine if three non-turf groundcovers with reputations for using low amounts of water actually use less water than Kentucky bluegrass (KBG). Irrigation treatments were based on percentages of ET (100%, 75%, 50%, 25%, 0%) and calculated by the modified Penman equation. Results from the 1991 season indicate that at the 100% and 75% treatments Potentilla tabernaemontani and Cerastium tomentosum were significantly better than the other species in terms of establishment and vigor but quality declined significantly at rates below 75%. At the 50% rate both KBG and Sedum acre maintained good quality although growth was slow. At the 25% rate, quality of KBG significantly declined while Sedum acre maintained good quality. Quality of Sedum acre declined only slightly at the 0% treatment and would be a good alternative to KBG if water conservation was a high priority in the landscape.
James E. Klett and David Staats
Herbicides were applied to container grown landscape plants and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. Three preemergent herbicides were applied including: Oxadiazon (Ronstar) at 4.54 and 9.08 kg/ha, Oxyfluorfen + Oryzalin (Rout) at 3.41 and 6.81 kg/ha and Oryzalin (Surflan) at 2.27 and 4.54 kg/ha. There was also a weedy and non-weedy control. The plant species included: Syringa vulgaris (Common Lilac), Wisteria sinensis (Chinese Wisteria), Phlox paniculata (Garden Phlox) and Dahlia hybrid (Garden Dahlia). They were all grown in number one containers in a media of soil, spaghnum peat moss, and plaster sand (1:2:1 by volume). All herbicides tested controlled weeds effectively with no phytotoxicity except with Phlox paniculata. Oryzalin resulted in a phytotoxic effect on Phlox paniculata at both the 1x and 2x rates.
David Hillock and James E. Klett
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.
James E. Klett and David Staats
During the 1999 season, preemergent herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. The herbicides and rates were: Oxyfluorfen + Pendimethalin (Scotts Ornamental Herbicide II) 3 and 6 lb ai/A, Napropamide (G) (Devrinol) 3 and 6 lb ai/A, Oryzalin (Surflan) 2 and 4 lb ai/A, Oxadiazon (Ronstar) 4 and 8 lb ai/A, Oxyfluorfen + Oryzalin (Rout) 3 and 6 lb ai/A, Prodiamine (Barricade) 0.65 and 1.3 lb ai/A, Pendimethalin (Scotts Ornamental Weedgrass Control) 2 and 4 lb ai/A, Trifluralin (Treflan) 4 and 8 lb ai/A. Herbicides were applied to Penstemon mexicali `Red Rocks'™, Osteospermum barberiae compactum `Purple Mountain'™, Gazania linearis `Colorado Gold'™, Agastache rupestris, Diascia integerrima `Coral Canyon'™, and Zauschneria arizonica. All plant and herbicide combinations did not result in any significant decline in plant growth. All herbicides provided good weed control.
James E. Klett and Carl Wilson
Four woody plant species were grown during the 1988 and 1989 growing seasons under three irrigation treatments at two sites in two soil types. The three irrigation treatments which were implemented included: 1) control, 2) drip irrigated with no water stress, and 3) drip irrigated with water stress. Rainfall and additional water applied during the 1988 and '89 growing seasons were recorded. Analysis of this data showed the no stress treatment receiving more water at both sites, especially in 1989. After two years of growth, no statistical differences in new growth (height) were observed with any plant species evaluated at either site from the three water treatments. Comparing new growth, no statistical differences were observed except with Juniperus sabina. No visual differences were observed with Ribes alpinum and Cornus sericea. Visual differences were observed with Potentilla fruticosa and Juniperus sabina. The experiment will be continued during the 1990 growing season.
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.
James E. Klett, Laurel Potts, and David Staats
During the 1998 season, preemergent herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. The herbicides and rates were: Napropamide (Devrinol 10G), 0.72 and 1.44 kg a.i./ha; Oryzalin (Surflan 40AS), 0.36 and 0.72 kg a.i./ha; Oxadiazon (Ronstar 2G), 0.72 and 1.44 kg a.i./ha; Oxyfluorfen + Oryzalin (Rout 3G), 0.54 and 2.16 kg a.i./ha; Oxyfluorfen + Pendimethalin (Scott's OH II), 0.54 and 1.09 kg a.i./ha; and Trifluralin (Treflan 5G), 0.72 and 1.44 kg a.i./ha. Herbicides were applied to Phalaris arundinacea `Picta', Scabiosa caucasica, Sedum × `Autumn Joy', Pennisetum setaceum `Rubrum', Salvia argentea, Penstemon × mexicali `Red Rocks', Osteospermum barberiae v. compactum `Purple Mountain', and Gazania linearis `Colorado Gold'. Phytotoxicity symptoms (visual defects) were apparent with Napropamide on Phalaris (at both rates) but recovered by the end of season. All herbicides provided good weed control.
Scott W. Dunn and James E. Klett
Perennials grown in 5.7-cm containers received two root treatments (mechanical root-pruned and non-pruned) prior to field planting. During the 1996 season, the two root treatments and five irrigation treatments, (0%, 25%, 50%, 75%, 100%) ET0 (reference crop evapotranspiration), were tested on Delosperma cooperii, Delosperma nubigenum, Polygonum affine, and Veronica liwanensis and evaluated on the basis of plant growth and visual ratings. No significant change in height occurred in any species for both root or irrigation treatments. No significant change in width or density occurred in D. cooperii, from root treatment; however irrigation treatments below 50% resulted in a significant decrease in width. Significant deceases in width also occurred in all species from irrigation treatments. Mechanically root-pruned plants resulted in a significant decrease in density of D. nubigenum, P. affine, and V. liwanensis and a decrease in width in P. affine.
Amy Jo Waldo and James E. Klett
Ninety trees are being used and have been in the field since 1994. The three species studied include: Fraxinus pennsylvanica Patmore (Green Ash), Quercus macrocarpa (Bur Oak), and Pinus nigra (Austrian Pine); 30 of each species. Each species has been harvested in three different nursery production methods including balled and burlapped, plastic container, and fabric container. During the 1996 growing season, the following data was recorded for each tree, growth increments, caliper size, and tree heights. For the two deciduous species, both dry weights and leaf area were recorded. Some sap flow measurements were taken using a non-intrusive stem heat balance method, on the same tree species with varying production methods. All three species showed the greatest growth increments and heights for those trees planted in fabric containers. In regards to trunk caliper size, Pinus nigra showed that the balled and burlapped, and fabric containers had larger calipers than those planted in plastic containers. Fabric container trees were larger in caliper than plastic container trees, which was larger than the balled and burlapped on Quercus macrocarpa. The plastic container and balled and burlapped resulted in greater calipers on Fraxinus pennsylvanica than the fabric containers. Quercus macrocarpa also showed that both leaf area and dry weight were greatest for trees planted in fabric containers, followed by the other production methods. Trees in plastic containers exhibited the greatest leaf area and dry weight for Fraxinus pennsylvanica. Overall, the fabric container trees in all three species illustrated the highest-quality trees, followed by those planted in plastic containers, and then balled and burlapped. Minimal data was recorded for transpiration rates in 1996 and will be further investigated in 1997.
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.