On 2 Feb. 1996, rooted cuttings of Pelargonium × hortorum L. H. Bailey cvs. Tango and Blues were planted in 750-cm3 (14 cm in diameter) pots containing peatmoss mixed with shredded tire rubber (2–6.0 mm particle size) at 0%, 20%, 40%, 60%, or 80%. Plants were irrigated by hand, drip, or ebb-and-fl ood, and were arranged in a split-plot experimental design. A wetting agent (Aqua Gro 2000 L, Aquatrols Corporation, Cherry Hill, N.J.) was mixed at the rate of 6 ml per 3750 ml of water and 120 ml of solution was applied to each plant. Greenhouse studies indicated that geraniums could be grown successfully in media containing up to 20% shredded tire rubber by volume when irrigated by hand. Plants grown in media containing more than 20% rubber were observed to be slow-growing and chlorotic. Tissue analysis of the plants indicated significantly increased levels of zinc in plants grown in media containing high percentages of rubber. Geraniums grown in media containing 80% rubber and irrigated using ebb-and-fl ood benches had the significantly highest levels of foliar zinc. Media porosity, percent air space, and bulk density increased, while water holding capacity decreased with increasing amounts of shredded tire rubber added to the media.
Mohammad Baqir and Richard L. Harkess
Lynn Burney and Richard L. Harkess
Maintaining annual color throughout the long summer season in warm temperate regions has become an interest to landscapers and nursery operators. Some colorscaping companies have begun implementing a second summer planting season. There is little information available concerning suitable cultivars and species of bedding plants for establishment in late summer. This study examined plant establishment in two container sizes and three dates of transplanting to determine late season establishment in Starkville, Miss. (33°27' latitude, 88°49' longitude). Seeds of 27 different cultivars were grown in plug flats in the greenhouse and transplanted into jumbo 606 or 10-cm square containers. The plants were grown in the greenhouse until transplanting on 16 Aug., 30 Aug., or 13 Sept. 1996. The plants were transplanted into plots containing nine plants with three replications per planting date. The plants were spaced on 20-cm centers among and between plots. The earliest two plantings resulted in better plant establishment and floral display. Some of the cultivars and species were more tolerant of the late season temperature and humidity establishing and providing a good color display from 6 weeks after transplanting until frost, 2 Nov. 1996. Cultivars that performed well included: Impatiens wallerana `Deco Crystal', `Expo Lavender Blush', `Dazzler Salmon', Begonia semperflorens `Varsity Bronze Scarlet', Zinnia `White Pinwheel', Tagetes erecta `Marvel Gold', and Tagetes patula `Bonanza Harmony'. Cultivars that did not establish well under these conditions included: Verbena hybrida `Romance Pink' and Salvia splendens `Salsa Salmon'. The container size did not significantly affect plant establishment.
Amir Rezazadeh and Richard L. Harkess
Purple firespike (Odontonema callistachyum), native to Central America, has potential for use as a new flowering potted plant. The effects of number of pinches (zero, one, or two) and number of cuttings (one, two, or three) per 6-inch pot were evaluated on the control of plant height. Plant height was suppressed as the pinch number increased. The greatest reduction was recorded with one cutting per pot and two pinches. The maximum number of branches per pot was recorded with two pinches and three cuttings per pot. In a second experiment, plant growth regulators (PGR) were also tested for efficacy of height control; 2 weeks after pinching, foliar sprays of paclobutrazol, flurprimidol, daminozide, chlormequat, and a tank-mix of daminozide + chlormequat or media drenches of paclobutrazol, uniconazole, or flurprimidol were applied. Plant height, leaf area, and leaf dry weight were recorded at 3, 6, and 9 weeks after PGR application. Maximum height control was obtained with uniconazole drench at 8 ppm, resulting in plants 22 cm tall, 61% shorter than the untreated control (56 cm); however, it resulted in severe leaf distortion. Plant height was 56% and 46% shorter than the control using drenches of paclobutrazol at 30 ppm and flurprimidol at 15 ppm, respectively. Daminozide spray at 2000 ppm and tank-mix of daminozide + chlormequat at 4500/1500 ppm suppressed stem elongation by 20.3% and 19%, respectively. Plants treated with paclobutrazol drench at 30 ppm reduced leaf area and leaf dry weight compared with other PGRs. Chlormequat spray at tested concentrations was ineffective for controlling firespike plant growth. The most attractive potted plants were produced using a drench application of paclobutrazol at 10 or 15 ppm.
Scarlett L. Walker and Richard L. Harkess
Flowering of Impatiens hawkeri Bul. during production results in an accumulation of dead plant material and directs energy away from vegetative growth. Ethephon is currently used at 500 ppm during the production of cuttings to eliminate flowering on stock plants. In this study, the timing and rate of ethephon application during production was examined. Two cultivars were used: `Innocence' and `Shadow'. Ethephon was adjusted to pH 5.0 and applied at planting (0), or 1, 2, 3, or 4 weeks after planting at 0, 250, or 500 ppm. An additional control of water adjusted to pH 5.0 was also included. Five replications were used in a completely randomized experimental design. The experiment was conducted twice—26 June 26 and 7 Oct.1995—each lasted 10 weeks. The number of branches, plant size, fresh:dry weight ratio, and days to first flower were recorded. `Innocence' did not significantly respond to the treatments, except for branch number and fresh:dry weight ratio, which decreased when treated with ethephon. In `Shadow', a treatment of ethephon at 250 ppm 1 or 3 weeks after transplanting provided the best control of flowering with a minimal delay in production and high plant quality.
Richard L. Harkess and Robert E. Lyons
Combinations of seed rate, spacing and weed control treatments were evaluated for their effect on the performance of The Virginia Tech Transplanted Meadow technique. The treatments consisted of seed rates of 112 g or 56 g per 90 m-2; within-row transplant spacing of 30, 45, or 60 cm; and mulch, oryzalin, or nothing applied for weed control. Plant competition alone was insufficient for effective weed control whereas oryzalin was the best but also reduced the plant stand and floral display. Mulch provided effective weed control with maximum floral display. Close transplant spacing within rows resulted in quick site coverage but this advantage disappeared after 8 weeks when no difference in floral display was observed. Seeding rate did not affect site coverage until the meadow reached maturity at 12 weeks. The lower seed rate allow ed more lodging, resulting in a more open appearance and greater light transmission through the canopy. Chemical name used: 4-(dipropylamino)-3,5dlnitrohenzenesulfonamide (oryzalin).
James M. Rawson and Richard L. Harkess
Three experiments were conducted using Lagerstroemia `Victor' and `Zuni', one on pinching, another on photoperiod, and the third with fertilizer rates. Liners were potted with either one or three liners per container. In the pinching experiment, treatments were 0, 1, 2, 3, or 4 pinches at 0, 2, 4, or 6 weeks after planting. In the photoperiod experiment the plants were exposed to 0, 4, 8, or 12 weeks of short days before being moved to long days. In the fertilizer experiment the plants were fertilized at 0, 200, 400, 600, or 800 mg.L-1 nitrogen from 20-10-20 liquid feed and 0 or 6 g per container of 15-11-13 slow-release fertilizer. For both `Victor' and `Zuni', three liners per container resulted in plants that were wider and shorter than those with only one liner. Neither timing nor number of pinches significantly affected plant size. Short days prevented vegetative growth and floral development in both cultivars. `Victor' grew and flowered best after receiving 8 weeks of short days before moving to long days. `Zuni' grew and flowered best when moved directly to long days after potting. Both `Victor' and `Zuni' grew best when receiving either 200 mg·L-1 or 6 g of slow-release fertilizer.
Janet Waterstrat, Jacquelyn Deeds and Richard L. Harkess
Recent trade journals and magazines report a widespread and increasingly popular trend encouraging the use of native plants in the landscape. A random sample of 528 Southern Nurserymen's Association 1996 members were surveyed to determine 1) if they had perceived the trend reported in trade and consumer publications towards the selection of native plants, and 2) if there are consistencies in demographic characteristics and aspects of advertising plans among the respondents. Forty-two percent of those surveyed responded. Respondents perceived an overall interest in native plants higher in 1996 than in 1991. Almost half of the respondents had increased quantity and variety of native plants in response to their perceptions; 28% had not responded in any way. Plant professionals who had responded to the perceived trend did not differ significantly from those who had not on selected demographic characteristics. Selected aspects of advertising did not differ significantly except for the extent to which consumer magazines were used as references for marketing strategies.
Robert F. Brzuszek and Richard L. Harkess
Recent studies have shown that the use of native plants by landscape architects and contractors in the southeastern United States has increased as has the clientele interest level in native plants. Recommendations to increase the use of native species by the landscape industry in this region include increasing the number of nurseries carrying native plants and the quantities and species currently available. To understand how green industry professionals view the opportunities and constraints of the current southeastern United States native plant market and to synthesize the connections between landscape architect's demands and the supplies of the nursery industry in this region, a questionnaire was developed and e-mailed to southeastern U.S. wholesale and retail nurseries in six states. The survey included questions regarding nursery stock, demand, and species sold. A total of 129 responses were received, and they revealed that while there is a perceived increase in customer interest in native plants, market demand and enhanced public education play a key role in further development of this growing market.
Amir Rezazadeh, Richard L. Harkess and Guihong Bi
Red firespike (Odontonema strictum) is an ornamental shrub with potential for use as a flowering potted plant due to its dark green foliage and attractive red flower spikes. To stimulate branching and improve quality of red firespike, foliar spray applications of dikegulac sodium (DS) and benzyladenine (BA) and hand pinching were evaluated across two seasons (Spring and Summer 2014). There were three pinching treatments: one, two, or three pinches. Plant growth regulators (PGRs) were applied at 400, 800, 1600, or 2400 ppm DS or 600, 1000, 1250, or 1750 ppm BA. Both studies included an untreated control. Red firespike treated with all concentrations of BA and 1600 and 2400 ppm DS had increased branching compared with the control, except 1000 ppm BA in Expt. 1. Pinching did not affect the number of branches. Dikegulac sodium at 1600 and 2400 ppm and all concentrations of BA resulted in shorter plants than the control. Phytotoxicity was observed in plants treated with 1600 or 2400 ppm DS. In both experiments, DS at 1600 and 2400 ppm had the least plant dry weight compared with the control. Treatment with BA at 1750 ppm resulted in greatest leaf area compared with control. Dikegulac sodium at 800 ppm increased the number of flowers compared with control. Pinching and BA did not affect number of inflorescences. All concentrations of BA and DS delayed flowering, except 1000 ppm BA. Plants treated with 800, 1600, and 2400 ppm DS had shorter inflorescences compared with control plants. Benzyladenine decreased the length of the inflorescence at high concentrations, 1250 and 1750 ppm. Pinching treatments did not affect inflorescence length.
Amir Rezazadeh, Richard L. Harkess and Guihong Bi
This study evaluated the effects of paclobutrazol (PBZ) and flurprimidol on the morphological and physiological characteristics of potted red firespike (Odontonema strictum) under drought stress. PBZ and flurprimidol were applied as a soil drench at 0.24 mg/pot. Untreated plants acted as a control. The plants were exposed to drought stress 2 weeks after plant growth regulator (PGR) application. Another group of plants treated with PGRs was watered regularly. A reduction in plant height, plant diameter, and growth index (GI) was observed in plants treated with PGRs and drought stress 5 weeks after beginning the study. Drought stress reduced plant height by 45% compared with control. Flurprimidol under drought stress decreased plant diameter and GI by 36% and 76%, respectively, compared with the control. The least leaf area and plant dry weight were observed in plants drenched with flurprimidol and grown under drought stress. Drought stress also delayed flowering and the number of plants flowering. Plants treated with PBZ had the highest photosynthesis rate, 54% more than untreated plants under drought stress alone. The lowest stomatal conductance (g S) was measured in plants under drought stress alone or drought plus PBZ. Application of PBZ-enhanced red firespike drought tolerance reducing adverse effects of water stress on photosynthesis during the experiment.