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- Author or Editor: Gary J. Keever x
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.
`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),
Abstract
Four methods of overwintering container-grown ornamental nursery stock were evaluated. Canopy temperatures of plants unprotected or covered with a thin layer of ice closely followed air temperatures during subfreezing conditions; minimum ambient air temperature was – 16C. Canopy temperatures under white copolymer film fluctuated widely, while canopy and growth medium temperatures of plants continuously irrigated during subfreezing temperatures did not drop below 0C. Root injury of all species and foliar injury of azalea (Rhododendron × ‘Due de Rohan’), euonymus (Euonymus japonica Thunb. ‘Microphylla’ H. Jaeg.), and pittosporum [Pittosporum tobira (Thunb.) Ait.] were least when plants were continuously irrigated or covered with white copolymer film. Foliage of Japanese holly (Ilex crenata Thunb. ‘Compacta’) and dwarf Burford holly (Ilex cornuta Lindl & Paxt. ‘Burfordii Nana’) was not injured with any treatment. Bark splitting of azaleas was most severe under the thinly iced and white copolymer-covered treatments, less severe in the unprotected treatment, and least with continuous irrigation.
Container-grown pecan [Carya illinoensis (Wangenh.) C. Koch] trees with “mouse-ear” symptoms, characterized by small, rounded, cupped, and slightly wrinkled leaflets, were repotted into two types of media amended with three rates of dolomitic limestone (0, 5.4, or 10.7 kg·m-3). In both media [4 milled pine bark: 1 sand; 1 soil: 1 peat: 1 perlite (by volume)], mouse-ear symptoms in the season following repotting were dramatically reduced at the lower lime application rates. Medium Fe, Ca, Cu, and Mn and foliar Ca, Mg, Mn, Zn, and B were affected by lime rate 10 months after repotting in one or both media. Medium pH increased quadratically as lime rate increased. Greatest plant recovery occurred when no lime was added, resulting in a pH of 3.9 in the bark-sand medium and 4.2 in the soil-peat-perlite medium.
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.
`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.
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.
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.
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.