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Allison L. Byrd, Velva A. Groover and Holly L. Scoggins

Herbaceous perennials comprise one of the fastest-growing segments of floriculture crop production. Little information has been published regarding their mineral nutrition requirements, specifically nutrient foliar standards and nutrient deficiency symptoms. Our research documents visual symptoms of nutrient deficiencies in the chronological order in which they appear from incipient to advanced stages, and establishes foliar analysis standards by correlating nutrient levels with initial and advanced stages of symptoms for nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, copper, zinc, manganese, molybdenum, and boron. Rooted cuttings were grown for as many as 12 weeks in a hydroponic system with modified Hoagland's solution minus the element of interest, along with complete nutrient solution controls. Taxa selected for study were representative of commonly grown varieties and of differing families; Verbena canadensis `Homestead Purple' (clump verbena), Heliopsis helianthoides `Bressingham Doubloon' (false sunflower) and Veronica × `Goodness Grows' (speedwell). Days to incipient deficiency symptoms ranged from 5 to 60. Chronological order of appearance was consistent with Fe and Ca symptoms appearing within 10 days for all three taxa. Other deficiency symptoms varied both by taxa and in chronology. Root and shoot dry weights were closely and positively correlated with time to incipient deficiency.

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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.

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James Klett*, Dave Staats and Matt Rogoyski

During the 2003 season, preemergence herbicide was applied to twelve container grown herbaceous perennials and woody plants and evaluated for weed control, phytotoxicity, and effect on plant growth. The herbicide and rates were: Flumioxazin (Broadstar) 113.5 g (label rate), 227 g and 454 g a.i./A. Herbicides were applied to Buxus microphylla `Winter Gem', Cytisus purgans `Spanish Gold', Festuca ovina glauca `Elijah Blue', Hakonechloa macra `Aureola', Lonicera tatarica `Arnold Red', Pachysandra terminalis `Green Sheen', Hydrangea arborescens `Annabelle', Mahonia aquifolium, Phalaris arundinacea `Picta', Carex buchananii, Cerastium tomentosum, and Achillea millefolium `Red Beauty'. Weed control was excellent at all rates and controlled at least 99% of all weeds. No phytotoxicity symptoms were apparent on Mahonia, Buxus, Cytisus, Festuca, Hakonechloa, Pachysandra or Phlaris. Phytotoxicity resulted on some of the other plants. Carex had smaller plants (dry weights) at all rates. Cerastium had severe phytotoxicty at the 227 g and 454 g rates and moderate stunting at the recommended label rate, 113.5 g. Hydrangea became chlorotic and stunted at the 113.5 g rate and some fatal toxicity ocurred at the 227 g and 454 g rates. Phytotoxicity resulted on Lonicera at all rates and ranged from mild chlorosis in leaf veins (113.5 g rate) to plant death (454 g rate). Achillea at the 113.5 g rate only resulted in stunted plant growth while the 227 g and 454 g rates resulted in severe phytotoxcity and plant death.

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Scott Dunn, David Staats and James E. Klett

During the 1996 season, pre-emergent 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/ha; Oxyfluorfen + Pendimethalin (Scott's OH II),0.54 kg a.i./ha; and Trifluralin (Treflan 5G), 0.72 and 1.44 kg a.i./ha. Herbicides were applied to Campanula carpatica, Dianthus gratianopolitanus, Gaillardia × `Baby Cole', Penstemon × `Husker's Red', and Phlox subulata `Emerald Blue'. Phytotoxicity symptoms (visual defects and less height) were apparent with Oryzalin on Penstemon (at both rates) and on Phlox (0.72 kg a.i./ha). Weed control was significantly less with Trifluralin and Napropamide when compared to the other herbicides.

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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.

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David Staats, James Klett, Teri Howlett and Matt Rogoyski

During the 2005 season, three preemergence herbicides were applied to four container-grown herbaceous perennials and evaluated for weed control, phytotoxicity, and effect on plant growth. The herbicides and application rates were: 1) Pendimethalin (Pendulum 2G) 2.24, 4.48, and 8.96 kg/ha; 2) Trifluralin and Isoxaben (Snapshot 2.5 TG) 2.8, 5.6, and 11.2 kg/ha; and 3) S-metolachlor (Pennant Magnum 7.6 EC) 2.8, 5.6, and 11.2 kg/ha. Herbicides were applied to Coral Bells (Heuchera sanguinea), Hopflower Oregano (Origanum libanoticum), CORONADO™ Hyssop (Agastache aurantiaca), and SPANISH PEAKS™ Foxglove (Digitalis thapsi). Treatments were applied twice with 30 days between applications. Plants were evaluated for phytotoxicity after 1, 2, and 4 weeks after applying herbicide treatments. No phytotoxicity symptoms were apparent on any of the plants treated with Pendulum, and plant size (dry mass) was not affected. Snapshot resulted in visual phytotoxicity with Digitalis and Heuchera at the higher rates and also resulted in smaller plants. Pennant Magnum caused phytotoxicity at all rates in all plants and resulted in significantly smaller plants than the control. Weed control was very good with all herbicides, but did not control every weed.

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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.

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Genhua Niu and Denise S. Rodriguez

In order to use reclaimed water to irrigate landscape plants and minimize damage and loss, salinity tolerance of commonly used landscape plants needs to be identified and characterized. Eight herbaceous perennials and groundcovers were obtained from a nursery, transplanted to 2.6-L plastic containers, and grown in the greenhouse for 2 weeks before salinity treatments (1.0, 3.2, 6.4, and 12 dS·m-1) were initiated. Plants were irrigated with measured amounts of saline solutions to obtain a 30% leaching when ≈50% water was depleted. After 12 weeks, half of the plants in each treatment were destructively harvested and dry weights of shoots and roots were taken. Three Penstemon species (pseudospectabilis, eatoni, and strictus) and Lavandula angustifoliaat 6.4 and 12 dS·m-1 and most of them at 3.2 dS/m did not survive. Shoot dry weight of Delosperma cooperidecreased by 25% at 12 dS·m–1, but there were no significant differences among the rest of the treatments. All plants of Teucrium chamaedryssurvived, but growth was reduced significantly with lower visual scores as salinity of irrigation water increased. Although growth was reduced in Gazaniarigensas salinity increased, no other signs of stress were observed. Ceratostigma plumbaginoides had less growth at 3.2 dS·m–1, and older leaves showed reddish pigmentation at 6.4 dS·m-1, whereas those at 12 dS·m-1 did not survive. Among the tested species, D.cooperiand G.rigensindicated a high tolerance to salinity; T. chamaedrysand C. plumbaginoides were moderately tolerant; and the rest were salt sensitive.

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Alison Frane, Royal Heins, Art Cameron and William Carlson

A 4-hr night interruption (NI) is an effective way to promote flowering in many long-day herbaceous perennials. Some perennials are grown outdoors in the early spring and often are exposed to low night temperatures. Long days delivered by NI lighting ineffectively promote flowering under low-temperature conditions in some long-day species. The objective of this experiment was to determine the effectiveness of NI long-day lighting treatments delivered at different night temperatures in promoting flowering of several herbaceous perennials. Ten herbaceous perennial species were grown under natural short days augmented with a 4-hr NI. Night temperatures were 2.5, 5, 10, 15, 20, and 25°C with day temperature of 25°C for all treatments. Plants were transferred to 9-hr days at a constant 20°C after 7 weeks of treatment. Results on flowering percentage, date of visible bud and flowering, node count, flower bud count, and plant height at flowering will be presented.

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L.M. Beckett, B.K. Behe, C.F. Deneke and C.H. Gilliam

There are indications that the U.S. herbaceous perennial plant industry has grown substantially in the last decade. Government census data on perennials is sparse, very general, and collected infrequently. The objective of this research was to define characteristics of the herbaceous perennial plant industry. Questionnaires were sent to members of the Perennial Plant Association in 1990. We requested that the person who made decisions on a daily basis, the owner or active manager, respond. Of 439 surveys distributed, 147 were returned for a 33.5% response rate. The average owner or active manager had a high education level (16 years) which was combined with management experience in at least one other company. Firms sold a mean of 30 genera of perennials. Firms selling primarily perennials were younger and more likely to have less total sales than firms selling primarily other plant products. Firms marketing primarily perennials were more likely to sell products by mail and offer a wider selection of genera.