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Jeff S. Kuehny, Matt Taylor, and Michael R. Evans

Biodegradable and plastic containers were evaluated for greenhouse and landscape production of ‘Score Red’ geranium (Pelargonium ×hortorum), ‘Grape Cooler’ vinca (Catharanthus roseus), or ‘Dazzler Lilac Splash’ impatiens (Impatiens wallerana) at Louisiana State University (LSU), Baton Rouge, LA; Longwood Gardens (LWG), Kennett Square, PA; and University of Arkansas (UA), Fayetteville, AR. Of the 5-inch containers, the highest geranium and vinca shoot growth occurred in plastic containers compared with bioplastic and rice straw containers. Of the 4-inch containers, paper containers produced the greatest geranium shoot growth compared with the peat containers at LSU and LWG. Shoot growth in impatiens was similar for all container types at all three locations. When all container types were considered, there was no difference in the root growth of geranium or impatiens at all three locations. However, vinca had the highest root growth in paper containers compared with that in peat and coconut fiber. The root:shoot (R:S) ratio of geranium were mixed for all pot sizes, types, and locations. Vinca R:S ratio was highest in both the 4- and 5-inch plastic control containers at LSU and lowest in both plastic containers at LWG. Direct plant containers generally performed well in the landscape as the plants grown in plastic containers at LWG. Plants grown in all tested containers produced marketable plants for both the retail and landscape markets. However, growers and landscapers should be aware of growth differences that may occur when using biodegradable containers and align production practices accordingly.

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T.K. Howe and W.E. Waters

Nineteen vinca (Catharanthus roseus) cultivars were evaluated for days to flower, flower diameter, flower color, plant dimensions, and appearance during the summer and fall of 1993. Summer: Days from sowing to flower ranged from 58 days for `Pretty in Pink' to 64 days for `Pretty in Rose'. Flower diameter ranged from 4.3 to 5.8 cm for `Orchid Cooler' and `Parasol', respectively. `Parasol' produced the largest flower. The `Carpet' entries (creeping types) were shorter than all others. Appearance ratings were similar among all entries at 85 and 109 days after sowing. Fall: Days from sowing to flower ranged from 51 days for `Grape Cooler' to 58 days for `Tropicana Rose'. Flower diameter ranged from 4.3 to 5.1 cm for `Orchid Cooler' and `Parasol', respectively. `Peppermint Cooler', `Grape Cooler' and `Orchid Cooler' were the only entries with significantly smaller flower size than `Parasol'. Appearance ratings at 109 and 141 days after sowing were similar for all entries, however at 166 days `Dawn Carpet' and `Pink Carpet' had significantly lower ratings than 15 other entries due to frost damage.

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Michael R. Evans

Aggregates produced from finely ground waste glass [Growstones (GS); Earthstone Corp., Santa Fe, NM] have been proposed to adjust the physical properties of peat-based substrates. The GS had a total pore space (TPS) of 87.4% (by volume), which was higher than that of sphagnum peat and perlite but was similar to that of parboiled fresh rice hulls (PBH). The GS had an air-filled pore space (AFP) of 53.1%, which was higher than that of sphagnum peat and perlite but lower than that of PBH. At 34.3%, GS had a lower water-holding capacity (WHC) than sphagnum peat but a higher WHC than either perlite or PBH. The bulk density of GS was 0.19 g·cm−3 and was not different from that of the perlite but was higher than that of sphagnum peat and PBH. The addition of at least 15% GS to sphagnum peat increased the AFP of the resulting peat-based substrate. Substrates containing 25% or 30% GS had a higher AFP than substrates containing equivalent amounts of perlite but a lower AFP than substrates containing equivalent PBH. Substrates containing 20% or more GS had a higher WHC than equivalent perlite- or PBH-containing substrates. Growth of ‘Cooler Grape’ vinca (Catharanthus roseus), ‘Dazzler Lilac Splash’ impatiens (Impatiens walleriana), and ‘Score Red’ geranium (Pelargonium ×hortorum) was similar for plants grown in GS-containing substrates and those grown in equivalent perlite- and PBH-containing substrates.

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James E. Altland and Charles Krause

Switchgrass (Panicum virgatum) biomass is being evaluated as a potential alternative to pine bark as the primary potting component in containerized nursery crops. Substrates composed entirely of switchgrass have higher pH than what is considered desirable in container substrates. The objective of this research was to evaluate the influence of elemental S, sphagnum moss, and municipal solid waste compost (MSC) as amendments for reducing substrate pH and buffering it against large changes over time. Three experiments were conducted; the first two experiments were conducted using annual vinca (Catharanthus roseus ‘Pacifica Blush’) to quickly assess how pH was affected by the three amendments, and the final experiment was conducted with blueberry (Vaccinium corymbosum ‘Duke’) to assess the long-term effects of substrate amendments. Summarizing across the three experiments, elemental S was effective in reducing substrate pH; however, rates 1 lb/yard3 or greater reduced pH below the recommended level of 5.5 and lower S rates did not maintain lowered pH over time. Sphagnum moss and MSC together at 20% and 10% (v/v), respectively, were effective at reducing substrate pH and buffering against change. Sphagnum moss and MSC provided the additional benefit of improving physical properties of the switchgrass substrates.

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Timothy J. Smalley

Ornamental annuals were planted in field beds amended to a depth of 15 cm with 0, 98, 196, or 392 g·m–3 of Hydrosource (Western Polyacrylamide, Castle Rock, Colo.). Hydrosource is a sodium-based, cross-linked, polyacrylamide hydrogel. Salvia splendens `Redtop' and Catharanthus roseus `Peppermint Cooler' were planted on 3 June 1993 and sampled for dry shoot weight and growth index 6 and 12 weeks after planting. Salvia splendens `Red Hot Sally' and Begonia sempervirens `Vodka' were planted on 13 June 1994 in the same beds, with no additional amendments added, and were sampled for dry shoot weight and inflorescence weight 5 and 10 weeks after planting. Plants were irrigated as needed in both years until the first sampling date, and then irrigation ceased. For 1993, a dry experimental period, amending beds with Hydrosource increased dry weight and growth index of both annuals after 12 weeks. In 1994, a wet experimental period, Hydrosource increased shoot weight of plants after 5 weeks, but no differences existed among the weights of the plants after 12 weeks. The inflorescence weight increased with Hydrosource for salvia after 12 weeks. The data indicated that Hydrosource can increase growth of annuals during drought and have no detrimental effect on growth during a wet growing season.

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Holly L. Scoggins, Douglas A. Bailey, and Paul V. Nelson

There is a need for a substrate testing method suited for plug plant production. Methods currently used by most growers and analytical labs include the saturated media extract (SME) and the 2 water: 1 substrate (v/v) suspension. These methods are not particularly well-adapted to plug production. The press extraction (PE) method has been developed as a simple and quick alternative to these methods. However, interpretive standards for chemical analysis of plug substrates do not exist for PE. This study was designed to provide the necessary correlations between these methods to allow for development of pH, electrical conductivity (EC), and nutrient interpretive ranges for plugs. Plugs of begonia (Begonia ×semperflorens-hybrida Hort.), impatiens (Impatiens walleriana Hook. f.), marigold (Tagetes erecta L.), petunia (Petunia ×hybrida Hort. Vilm.-Andr.), salvia (Salvia splendens F. Sellow ex Roem. & Schult.), and vinca (Catharanthus roseus L.) were collected from commercial greenhouses and the substrate solution extracted with the PE, SME, and 1:2 methods. Plugs of begonia, celosia (Celosia argentea L. var. cristata (L.) Kuntze Plumosa Group), marigold, petunia, and vinca were grown with three fertilizer rates of 50, 150, and 250 mg·L-1 N. Shoots were harvested 30 days after planting and the solution was extracted from each flat using the three methods. For both experiments, PE EC was equal to or higher than the SME EC, and the pH was equal to or lower than the SME pH. The pH from the 1:2 was also similar to the PE. However, 1:2 EC results were consistently the lowest because of the dilution inherent in the 1:2 method. Interpretation ranges for pH and EC relationships were calculated to compare results from the PE with published sufficiency ranges for the SME and 1:2.

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Carrie L. Whitcher, Matthew W. Kent, and David Wm. Reed

The objective of this study was to quantify the optimum rates of water-soluble phosphorus (P) under constant nitrogen and potassium on the growth of new guinea impatiens (Impatiens hawkeri Bull.) `Paradise Violet' and vinca Catharanthus roseus `Pacifica Red' in soilless media in a recirculating subirrigation system. The experiment was designed so that only phosphate varied between treatments while all other nutrients remained constant. The ammoniacal N to nitrate N ratio was varied to counter balance increases in phosphate. Sodium was used as a counter ion to phosphate at higher concentrations of phosphate; sodium proved to be toxic at concentrations above 6 mm. In the new guinea impatiens experiment, there was a small increase in K due to the use of dibasic K phosphate to buffer pH. All growth parameters measured (height, leaf number, flower number, and shoot fresh and dry weight) showed significant differences with increasing P rate. Depending on the growth parameter measured, quadratic–linear models revealed an optimum P rate of 0.1 to 0.96 mm for new guinea impatiens `Paradise Violet' and 0.45 to 1.25 mm P for vinca `Pacifica Red'. For dry shoot weight, a common measure of optimum plant growth, the optimum P rate was 0.75 mm P for new guinea impatiens `Paradise Violet' and 0.67 mm P for vinca `Pacifica Red'. For flower number, a common measure of floral quality, the optimal P rate was 0.96 mm P for new guinea impatiens `Paradise Violet' and 1.25 mm P for vinca `Pacifica Red'. Electrical conductivity (EC) of the growing media increased significantly with increasing rate of P. At all rates, EC was significantly greater in the top layer than in the bottom and middle layers. The pH of the growing medium did not vary in relation to P concentration.

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Clydette M. Alsup and Pamela A. Trewatha

The rocky Ozarks soils make it difficult for some homeowners to establish ornamental gardens. An alternative to digging in rocky soils is planting into bags of potting soil. This study evaluated “Gardening in a Bag” for herbaceous bedding plants. The growth and appearance of Alternanthera, Capisum annuum, Dianthus, Gazania, Tagetes `Wave', and upright petunias, Salvia splendens, Spilanthes, Verbena, and Catharanthus roseus were evaluated in 2002 under two planting methods: in the ground vs. in bags of potting soil. Wave petunias, Dianthus, C. roseus, and Portulacagrandiflora were evaluated in 2003. All plants were mulched with 3 inches of coarse sawdust. In 2002, planting method had no effect on average height for 16 of the 25 cultivars tested. Seven cultivars were taller when grown in the ground while two cultivars were shorter in that treatment. Planting method had no effect on average plant width of 13 of the cultivars. Plant width was greater for nine cultivars grown in bags, while three cultivars were wider when grown in the ground. Visual ratings were similar for 14 of the cultivars, regardless of planting method. In 2003, performance of five species was evaluated on 3 and 29 July and 5 Sept. Plant height and width were greater on plants grown in the ground than plants grown in bags on 3 July and 5 Sept. Only plant width was significantly greater in the soil-grown plants on 29 July, although the greater height trend was still evident. Plants in the ground had more flowers than plants in bags on 3 July, but there were no differences in flower number the other two dates. Visual quality ratings were taken on the second and third dates, with no differences between treatments. Root soil temperature was higher in bags than in the ground on all three dates in 2003.

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Robert D. Wright, Brian E. Jackson, Michael C. Barnes, and Jake F. Browder

The objective of this study was to evaluate the landscape performance of annual bedding plants grown in a ground pine tree substrate (PTS) produced from loblolly pine trees (Pinus taeda) or in ground pine bark (PB) when transplanted into the landscape and grown at three different fertilizer rates. Begonia (Begonia ×semperflorens-cultorum) ‘Cocktail Vodka’, coleus (Solenostemen scutellarioides) ‘Kingswood Torch’, impatiens (Impatiens walleriana) ‘Dazzler White’, marigold (Tagetes erecta) ‘Bonanza Yellow’, petunia (Petunia ×hybrid) ‘Wave Purple’, salvia (Salvia splendens) ‘Red Hot Sally’, and vinca (Catharanthus roseus) ‘Cooler Pink’ were evaluated in 2005, and begonia ‘Cocktail Whiskey’, marigold ‘Inca Gold’, salvia ‘Red Hot Sally’, and vinca ‘Cooler Pink’ were evaluated in 2006 and 2007. Landscape fertilizer rates were 1 lb/1000 ft2 nitrogen (N) in 2005 and 0, 1, and 2 lb/1000 ft2 N in 2006 and 2007. Visual observations throughout each year indicated that all species, whether grown in PTS or PB, had comparable foliage quality in the landscape trial beds during the growing period. With few exceptions, dry weight and plant size for all species increased with increasing fertilizer additions, regardless of the substrate in which the plants were grown. For the unfertilized treatment, when comparing plant dry weight between PB and PTS for each species and for each year (eight comparisons), PTS-grown plant dry weight was less than PB-grown plants in three out of the eight comparisons. However, there were fewer differences in plant dry weight between PTS- and PB-grown plants when fertilizer was applied (PTS-grown plants were smaller than PB-grown plants in only 2 of the 16 comparisons: four species, two fertilizer rates, and 2 years), indicating that N immobilization may be somewhat of an issue, but not to the extent expected. Therefore, the utilization of PTS as a substrate for the production of landscape annuals may be acceptable in the context of landscape performance.

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Genhua Niu, Denise S. Rodriguez, and Yin-Tung Wang

The effect of drought on the growth and gas exchange of six bedding plant species—agastache [Agastache urticifolia (Benth.) O. Kuntze `Honeybee Blue'], dusty miller (Cineraria maritima L. `Silverdusty'), petunia (Petunia ×hybrida `Wave Purple'), plumbago (Plumbago auriculata Lam. `Escapade'), ornamental pepper (Capsicum annuum L. `Black Pearl'), and vinca [Catharanthus roseus (L.) G. Don `Titan']—was quantified under greenhouse conditions. Seeds were sown in January and seedlings were grown in the greenhouse until 18 Apr., when two irrigation treatments—drought (D, ≈18% volumetric moisture content at reirrigation) and control (C, ≈25% volumetric moisture content at reirrigation)—were initiated. Leaf net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration (E) were determined in response to a range of substrate moisture content (from ≈5% to 30% by volume) and temperature (from 20 °C to 40 °C). Dry weight of agastache, ornamental pepper, and vinca was unaffected by drought, whereas that of other species was reduced. Leaf area of plumbago and height of plumbago and vinca were reduced by drought. As substrate moisture content decreased from 25% to 10%, Pn, E, and gs decreased linearly in all species except petunia and plumbago. Leaf net photosynthetic rate of all species declined as leaf temperature increased from 20 °C to 40 °C. In contrast, E of all species, except petunia, increased as temperature increased. Transpiration rate of petunia increased as temperature increased from 20 °C to 30 °C, and then decreased between 30 °C and 40 °C. Although petunia had the highest Pn among the tested species, its Pn and gs declined more rapidly compared with the other species as temperature increased from 20 °C to 40 °C or as substrate moisture content decreased, indicating that petunia was most sensitive to high temperature and drought.