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Gary J. Keever

Eight species of container-grown woody landscape plants received a single foliar spray of 0, 25, 50, 100, or 200 mg a.i. ASC-66952 ·liter-1 on 13 June 1990. (ASC-66952 is a proprietary chemical being developed by ISK-Biotech.) Axillary, rhizomatous, and total shoot numbers of `Harbour Dwarf' nandina were increased with increasing concentrations of ASC-66952. Relative to those of the control plants, axillary shoot numbers were increased from 350% with 25 mg·liter-1 to 950% with 200 mg·liter-1, while rhizomatous shoot numbers were increased 144% with the lowest concentration and 477% with the highest concentration. Growth indices were decreased from 2.1% with 25 mg·liter-1 to 9.7% with 200 mg·liter-1. Branching and growth indices of other species tested were minimally affected by ASC-66952 application.

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Gary J. Keever and J. Raymond Kessler Jr.

In previous studies, night-interrupted lighting (NIL) promoted earlier flowering of summer-blooming herbaceous perennials grown under outdoor nursery conditions in the southeastern U.S. However, NIL promoted excessive plant height, thus reducing product quality. Our objective was to control plant height of Coreopsis grandiflora `Early Sunrise' (ES) and Rudbeckia fulgida `Goldsturm' (RG) grown under NIL with plant growth retardants (PGR) without offsetting earlier flowering promoted by NIL. Treatments under NIL were three rates of daminozide, daminozide plus chloromequat, flurprimidol, uniconazole, and NIL and natural controls. Plant height was reduced 3% to 38% in ES and 8% to 31% in RG and time to visible bud was unchanged by all PGR treatments compared to the NIL control. Time to visible bud was unchanged in RG by all PGR treatments and flurprimidol in ES, but the remaining PGR treatments increased time to visible bud compared to the NIL control in ES. Only ES plants treated with daminozide and daminozide plus chloromequat at the two highest rates and all rates of uniconazole were similar in height to the natural control. RG plant heights with the two highest rates of flurprimidol and uniconazole and the highest rate of daminozide plus chloromequat were less than the natural control; heights of plants in the remaining PGR treatments were similar to the natural control. Quality rating was unchanged in RG but was increased in ES by all PGR treatments compared to the NIL control.

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J. Raymond Kessler Jr. and Gary J. Keever

Vegetative offsets of Achillea x `Coronation Gold' were rooted under mist for 3 weeks and potted into 10-cm pots in a greenhouse. Plants were grown under short photoperiods for 6 weeks before being vernalized for 6 weeks at 6 °C. Plants then were provided long photoperiods from night-break lighting. Foliar sprays of daminozide at 0, 2550, 5100, or 7650 mg·L-1, chlormequat at 0, 767, 1534, or 3201 mg·L-1, daminozide + chlormequat at 0, 1275 +, 2550 + or 3825+1534 mg·L-1, flurprimidol at 0, 40, 80, or 120 mg·L-1, paclobutrazol at 0, 32, 64, 96, 128, or 160 mg·L-1 or uniconizole at 0, 11, 22, 33, 44, or 55 mg·L-1 were applied as a spray 1 week after vernalization. Highest market quality ratings were achieved with paclobutrazol at 96 or 128, uniconizole at 22 or 33, daminozide + chlormequat 3825 + 1534, chlormequat at 2301 or flurprimidol at 40 mg·L-1. Peduncle length and growth index decreased linearly for daminozide, chlormequat, and daminozide + chlormequat, and decreased quadratically for flurprimidol, paclobutrazol, and uniconizole with increasing rate. Time to flower increased most in treatments receiving high rates of daminozide. Flower diameter was reduced by the highest rates of flurprimidol and paclobutrazol.

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Gary J. Keever and William J. Foster

`Redwings' and `Gloria' azaleas (Rhododendron × `Redwings' and `Gloria') were treated with foliar sprays of uniconazole, paclobutrazol, or daminozide to suppress bypass shoot development and promote flower initiation and development. Uniconazole at 5 and 25 mg·liter-1 suppressed bypass shoot development of `Redwings' and `Gloria', respectively. Flowering of `Gloria', but not `Redwings', was delayed slightly with uniconazole sprays up to 25 mg·liter-1 ; with the highest uniconazole concentration, 200 mg·liter-1, flowering was delayed as much as 18 days. Flower count of `Gloria' was not affected by lower concentrations of uniconazole, but it was greatly reduced in both cultivars with concentrations above 75 mg·liter-1. Uniconazole was more active than paclobutrazol sprays of similar concentrations or than two daminozide sprays of 3000 mg·liter–1 . Chemical names used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (uniconazole); (2RS,3RS)-1-(4-chlorophenyl)-2-(1,1-dimethylethyl)-(1H-1,2,4,-triazol-l-yl-)pentan-3-ol (paclobutrazol); butanedioic acid mono(2,2-dimethylhydrazide (daminozide),

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J. Raymond Kessler Jr. and Gary J. Keever

Vegetative cuttings of Coreopsis verticillata `Moonbeam' were rooted under intermittent mist, pinched, and potted into 10-cm pots in a greenhouse. Plants were sheared to 6.5 cm above the pot rim 2 weeks after potting and given foliar sprays of daminozide at 0, 2550, 5100, or 7650 mg·L-1 or flurprimidol at 0, 50, 100, or 150 mg·L-1. Night-break lighting to provide long photoperiods was started the day of shearing. Growth retardants were applied at 0, 3, 6, 9, 12, or 15 days after shearing. Daminozide reduced shoot height, growth index, and lateral shoot length compared to the control by 69.3%, 69.2%, and 70.0%, respectively, while increasing quality rating by 67.3% and time to flower by 8 days at 5100 and 7650 mg·L-1. Response surface regression predicted that minimum plant size and maximum quality rating occurred when growth retardants were applied 5.7 to 8.3 days after shearing. Application timing had no effect on responses to flurprimidol. Shoot height, growth index, and lateral shoot length decreased quadratically with increasing rate while quality rating only improved compared to control. Flurprimidol did not cause a flowering delay.

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Gary J. Keever and Mark S. West

Uniconazole was applied once as a soil drench (15, 30, or 45 mg a.i./plant) or foliar spray (500, 1000, or 1500 mg liter-1, about 175 ml/plant) to established, field-grown thorny elaeagnus (Elaeagnus pungens Thunb. Fruitlandii) and leyland cypress [× Cupressocyparis leylandii (A.B. Jacks. & Dallim.) Dallim. & A.B. Jacks]. At the end of the second growing season following treatment, shoot dry weights (SDW) of thorny elaeagnus decreased with increasing rates of drench-applied uniconazole, while SDW of plants receiving the foliar application were not affected by increasing rates. Growth indices of leyland cypress, determined twice during the first growing season and at the end of the second growing season, were not influenced by application method or rate. Uniconazole applied as a soil drench at 15 to 45 mg a.i./plant suppressed growth of established thorny elaeagnus for at least two growing seasons, but leyland cypress was not affected by uniconazole drench or foliar spray at tested rates. No phytotoxicity was observed on either species in any treatment during the experiment.

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C. Frederick Deneke and Gary J. Keever

`Kees Nelis' tulips were potted five bulbs per 0.8-1 container using a commercial peat moss and perlite growing medium. Bulbs were exposed to 9C for 4 weeks, followed by 5C until the emerging shoots were 4 to 5 cm long. One day after plants were moved from the cooler to a greenhouse (14C minimum), the following treatments were applied: drench or spike (International Spike, Inc.) of 0.062, 0.25, or 1.00 mg paclobutrazol per pot; or drench of 0.25 mg ancymidol per pot. Flowering height was reduced linearly as concentration of paclobutrazol increased for both application methods; flowering height was 24.0 cm with the highest rate of paclobutrazol, 23.8 cm with ancymidol, and 27.7 cm with untreated plants. Treatments had no effect on flower diameter or time to flowering.

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Gary J. Keever and John A. McGuire

Container grown `Shishi-Gashira' camellias received a single foliar spray of 0, 5, 10, 15, 20, 40, or 60 mg a.i. liter uniconazole on 26 May 1989. Growth indices were determined about every 4 weeks during the 1989 growing season and following the spring 1990 growth flush. Flowering was also monitored. Growth was suppressed linearly or quadratically over the duration of the test, with growth inhibition 12 months after treatment ranging-l from 3.7% (5 mg a.i. liter-1) to 20.6% (60 mg a.i. liter-1) relative to the control Flower number increased from 52.6% (5 mg a.i. liter-1) to 100% (60 mg a.i. liter-1) compared to the control. Time to flower was not affected by 5 to 20 mg a.i. liter-1 uniconazol but increased 4 to 7 days with the 40 and 60 mg a.i. liter-1 rates. Uniconazole rate did not affect flower diameter.

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Gary J. Keever and C. Fred Deneke

Vegetative growth and flowering of Mandevilla `Alice du Pont' in response to foliar-applied uniconazole were determined in 3 experiments. Plants pruned to 2 nodes were treated with foliar applications of 30, 60, 90, and 120 ppm uniconazole. All uniconazole rates induced temporary leaf cupping and suppressed growth excessively for at least 6 weeks; thereafter, plants grew similarly to the control. Single applications of 5, 10, 15, and 20 ppm uniconazole were not effective in controlling vegetative growth, but multiple applications of 5.0, 7.5, 10.0, 12.5, 15.0, 17.5, and 20.0 ppm uniconazole provided acceptable, but not excessive, suppression of internode elongation. As the concentration of uniconazole increased, the interval between applications increased. Flowering was delayed and bloom size was reduced as uniconazole rate increased.