Potted Plant Production Research Articles

565 Use of Cooperative Learning Exercizes to Introduce Concepts in Potted Plant Production Classes

In production classes, students often commence the class by learning complicated crop-specific production cycles. Rarely are they afforded the opportunity of spending several class periods to first understand the major differences between commercial crops for production time, labor input, and market share. A cooperative learning exercise was created for the first week of lectures in potted plant production class (Hort 4051) at the Univ. of Minnesota (n = 18 students). Students were assigned to working groups for discussion and synthesis of the assignment. One week later, each group turned in their recommendations and one lecture session was devoted to in-class discussion of their answers. The exercise was in the form of a memo from a commercial company, Floratech, addressed to the students as the newly hired potted plant production specialists. In the memo, a graphical summary was presented of 13 major and minor potted crops, contrasting total production time, labor input, and market share for each crop. As production specialists, the student's primary task was to interact with all staff (other students role-playing various positions within the company) to answer the following question: “What is the most realistic, cost-effective location on the graph that Floratech should aim to move all crops?” Group discussions, both within and outside of class, focused on the noticeable trends depicted by the graph and the limiting factors that prevented crops from moving to the ideal location. Growers and breeders were quizzed on what factors kept each crop in the specific locations on the graph. The majority of student chose the midpoint of the graph as the best location. The exercise successfully peaked student's awareness of crop differences and the limiting production factors. Throughout the semester, students referred back to this graph to pinpoint the location for each crop covered.

574 Capital Investment Analysis of Adopting Zero Runoff Subirrigation Systems in Greenhouse Operations

Adoption of technology to achieve environmental stewardship and remain competitive is a high priority for greenhouse businesses. Zero runoff subirrigation (ZRS) technology offers great promise to manage fertilizer inputs while improving production efficiency. This study applied economic engineering methodology to quantify costs and returns associated with adopting ZRS systems and compare profitability of producing crops using alternative ZRS systems for greenhouse operations in the northeastern and north central United States. The production models showed that using ZRS systems to grow greenhouse crops can be profitable if growers select a system best suitable for their crop choices. Among the four ZRS systems studied (ebb-and-flow rolling benches, Dutch movable trays, flood floors and trough benches), the Dutch movable tray system returned the highest profit per square foot week (SFW) greenhouse area for small potted plant production ($0.244/SFW), and the flood floor system returned the highest profit when producing large potted plants ($0.002/SFW) and bedding crop flats ($0.086/SFW). The trough bench system was least profitable had the lowest profit for the two applicable crop categories—small potted plants ($0.183/SFW) and large potted plants (–$0.006/SFW). Sensitivity analysis showed that changes of cost variables generally did not affect the profitability rankings for alternative ZRS systems. Except for labor costs, as the hourly wage increased, the Dutch movable tray system gained advantages for small potted plant and large potted plant production. Among selected costs variables, changes in labor costs and tax rate had the highest impact on the profitability of small potted plant production, and changes in labor costs and initial investment costs had the highest impact on the profitability of large potted plant and bedding crop flat production.

206 Risk Analysis of Adopting Zero Runoff Subirrigation Systems in Greenhouses Using Monte Carlo Simulation

Although zero runoff subirrigation (ZRS) technology has great promise to manage fertilizer inputs while improving production efficiency in greenhouse operations, high initial investment costs and inadequate technical background are major impediments for initiating the change. In a world of uncertainty, greenhouse operators face the challenge of making an optimal investment decision to satisfy environmental compliance expectations and meet the companies' financial goals. Using Monte Carlo simulation, cost risk was analyzed to compare the relative risks of investing in alternative ZRS systems for greenhouse crop production. An investment model was defined for greenhouse production with alternative ZRS systems. Each cost variable was allowed to vary based on a probability distribution. Random numbers were generated to determine parameters for the probability distributions for the uncertain variables. The simulation process was repeated 300 times for each production model. Simulation results showed that among the four ZRS systems studied (ebb-and-flow benches, Dutch movable trays, flood floors, and trough benches), the Dutch movable tray system returned the highest average profit for small potted plant production and the flood floor system returned the highest average profit for large potted plant and bedding crop flat production. Risk of the production models were compared by the variability of simulation results. The Dutch movable tray system is the least risky for small potted plant production, and the flood floor system is the least risky for large potted plant and bedding crop flat production. Despite its low initial costs of adoption, the trough bench system was least competitive as a ZRS technology for a greenhouse operation because of the relative low profitability and high risk of production due to volatile profitability.

Bacterial Blight of Geranium: A History of Diagnostic Challenges.

Geraniums (Pelargonium spp.) have been an important part of greenhouse potted plant and bedding plant production for almost a century. Cultivars produced by vegetative propagation and by true seeds are grown and sold worldwide. In 1996, the wholesale value of geraniums exceeded $205 million in the United States alone (2). Pelargonium species are affected by a number of fungal diseases, including rust (Puccinia pelargonii-zonalis), gray mold (Botrytis cinerea), and root rot (Pythium spp.). Several bacteria and numerous viruses also cause diseases on geranium. Indeed, the most destructive disease of geraniums is bacterial blight (Xanthomonas campestris pv. pelargonii). Although hybrid geraniums grown from seed are susceptible to bacterial blight, it is the vegetatively propagated cultivars of florists’ geranium (P. × hortorum) and ivy geranium (P. peltatum) that are most commonly affected, because the causal organism inhabits the vascular tissue of infected plants and is carried in the cuttings. Munnecke (22) and Nichols (24) estimated 10 to 15% annual losses due to bacterial blight in the 1950s and 1960s, and such losses continue today (22,24). These loss figures are somewhat misleading because they are based on the industry-wide production of geraniums. In individual greenhouse operations, entire geranium crops have been destroyed by this disease. The reputations of several specialty propagators of Pelargonium have been ruined or severely damaged when these growers unknowingly sold infected cuttings and distributed them throughout the bedding plant industry. Despite efforts to eliminate this disease from geranium production systems, it continues to occur annually.

Modelling operational adaptations of tactical production plans on pot plant nurseries: a simulation approach

During the implementation of tactical production plans on pot plant nurseries actual conditions deviating from tactical planning premises may give reason for operational adaptation of the current plan. Therefore, in the present study, operational decision-making in pot plant production under uncertainty with respect to crop growth and price formation was analysed by means of simulation and subsequent regression metamodelling. Stochastic patterns of crop growth and price formation lead to considerable variation in annual net farm income. The regression metamodelling analysis, nevertheless, showed that more comprehensive strategies of operational decision-making improved profitability. Moreover, the largest improvement of profitability was found for inferior tactical production plans. In conclusion, operational decision-making may contribute to the nursery's profitability, although management costs and long-term effects should also be taken into consideration. ©

In vitro PPFD and media composition affect both in and ex vitro performance of Alstroemeria Butterfly-hybrids

The objective was to reduce in vitro production costs while retaining or improving plant quality, in particular the suitability for pot plant production. Plants were grown at photosynthetic photon flux densities (PPFD) of 0–40 μmol m-2 s-1 and sucrose concentrations of 3–7% during the multiplication phase and the effects of sucrose, BA, and NAA during root formation were investigated. Ex vitro growth were tested in both experiments. A small reduction in the rhizome multiplication rate was found with increasing PPFD and sucrose concentration. Increasing sucrose concentration reduced the number of aerial shoots. Aerial shoots were etiolated when cultured in darkness and their number increased with increasing PPFD at 3% sucrose, whereas PPFD did not affect the number of aerial shoots at 5 or 7% sucrose. During the multiplication phase a synergistic promoting effect of PPFD and sucrose was observed on root formation. Root formation after transfer to rooting medium was affected by sucrose and PPFD during the multiplication phase. PPFD did not influence root formation after propagation on 7% sucrose, whereas on 3 or 5 % sucrose root formation was gradually inhibited when PPFD was decreased below 17 μmol m-2 s-1. The formation of thick roots was promoted by propagation in light, and not influenced by sucrose concentration. Ex vitro growth was not affected by in vitro conditions, except for 7% sucrose during the multiplication phase that reduced flowering. Root formation on rooting medium was reduced by BA and promoted both by NAA and high levels of sucrose. The root inhibiting effect of BA could not completely be overcome by simultaneous application of NAA and high sucrose concentrations. Thick roots were only produced in the presence of NAA, and not affected by sucrose treatment. Ex vitro flowering was negatively influenced by the presence of BA during root formation and by high levels of sucrose if BA was absent in the rooting medium. High sucrose levels and NAA could partially compensate for the negative effect of BA on flowering.

Prediction of the Effects of CO2 Enrichment and Artificial Lighting on the Performance of a Greenhouse Production System: Application to Begonia × hiemalis Pot Plant Production

In this study, we tried to predict the influence of artificial lighting and/or CO2 enrichment on the production system of flowered Begonia x hiemalis pot plants. At this aim, a global simulation model was developed including the main four components of the production system: the external climate (stochastic model), the crop (growth and development model), the greenhouse and its equipment (physical model) and the grower (decisional model..Taking the gross margin of production as performance criterion of the system. the sirmulator was used to analyse the behaviour and the performance of the system with four configurations : a) only heating, b) heating and CO2 enrichment, c) heating and artificial lighting and d) heating, CO2 enrichment and artificial lighting.The simulation outputs gave useful information on the performances of these production strategies.

Validation of a Model for Simulating the Effect of Daminozide Application on Chrysanthemum

Daminozide is a growth retardant used in potted plant production as a foliar spray to inhibit shoot elongation. It has its greatest inhibitory effect immediately after application, becoming less pronounced thereafter; continued retardation is accomplished by reapplication at 7to 14-day intervals. A model for this retardation effect is useful in developing decision support tools, as well as in optimizing (perhaps minimizing) the use of this growth retardant. Such a model, as developed and described earlier, simulates the effect of a foliar spray application of daminozide at various concentrations on various days during the production cycle. The objective of this work was to validate this model for various varieties of chrysanthemum. Using the model to simulate the effect of one application of daminozide resulted in predicted plant heights very close to the observed heights for most of the varieties tested. Of four methods used to implement the multiple-application effect, two resulted in very good simulation of the observed plant heights. In summary, the model was shown to be valid for all the varieties of chrysanthemum tested.

Chemical and environmental manipulation of ornamental Acacia Mill. species for pot plant production

Chemical and environmental control of vegetative growth and flowering were investigated in ornamental Acacia species for pot plant production. High night temperature (20 °C/25 °C day/night vs. 25 °C/20 °C day/night) was ineffective in reducing height or width, but paclobutrazol (PBZ) controlled plant size of most species. Neither pruning nor 6-benzylamino purine (BAP) were effective in stimulating branching. Plants of some species flowered after 17 months from seed, but there was no stimulation of flowering by PBZ. Floral initiation of Acacia drummondii elegans occurred at both 15 °C day, 10 °C night ( 15 10 ) and 25 °C day, 20 °C night ( 25 20 ), but only plants at 15 10 flowered. Scanning electron microscopy showed that the flower buds at 25 20 had small underdeveloped anthers. Plants of five species were grown under 15 10 and 25 20 conditions for 6 months, after which time they were transferred between the two environments. All species produced fewer open inflorescences at 25 20 than at 15 10 , and some did not flower at 25 20 . Following transfer from 15 10 to 25 20 , flowering was reduced, in contrast with the plants transferred from 25 20 to 15 10 in which flowering was increased. The results show that flowering pot plants of Acacia can be produced using PBZ, and that manipulation of flowering time using low temperature is possible.

Alstroemeria plantlets can be induced to flowering by cold treatment during in vitro culture

Micropropagation seems to be the most promising method for large-scale production of Alstroemeria plantlets for pot plant production. Flowering of Alstroemeria is induced by cold treatments and if this can be an integrated part of the micropropagation process an efficient method for flower induction can be developed. To investigate flower induction, four temperature regimes (5, 10, 15 and 20 °C for 6 weeks) and three methods of reproduction (by seeds, rhizome division and micropropagation) were tested in nine genotypes. For micropropagated plants, temperature treatments were performed during root formation in vitro. Seedlings and rhizome divided plants were given the temperature treatment as established plantlets in 9 cm pots. For all reproduction methods flower induction was possible at temperatures of 15 °C or below. No substantial differences in the percent of flowering plants were observed between the reproduction methods. Genotypes reacted differently with respect to effective temperature ranges. In general, plants treated at 10 °C flowered faster, had the lowest number of aborted buds, the shortest flowering stems, and the highest percentage of reproductive stems as compared to those treated at other temperatures. The time from end of temperature treatment to flowering was longer for micropropagated plants than for the other plant types. This delay is probably not due to the in vitro culture per se, but to differences in plantlet size during the cold treatment. In a second experiment, root formation during in vitro culture was improved, resulting in a reduced time to flowering of the micropropagated plants. Reproductive stems were thicker than the vegetative stems and the diameter of emerging stems increased during ex vitro growth.

Iron toxicity in Pentas Lanceolata

Interveinal chlorosis of lower (oldest) leaves followed by development of interveinal necrotic spots, marginal necrosis, downward cupping of leaves, and leaf abscission were symptoms of a disorder commonly observed during production of potted pentas. The disorder was determined to be an Fe toxicity problem associated with accumulation of extremely high levels of foliar Fe (649 to 1124 ppm). Cultivars varied in their response to soil-applied Fe-DTPA chelate solutions: `Starburst', `Mauve' and `Ruby Red' were very susceptible, `Pink Profusion' was intermediate, and `White', `Lavender Delight', and `Pink Rose' were resistant. Potted plant production in a root medium with an initial pH of 6.7 ± 0.1 and a end pH of 6.4 ± 0.2 reduced the accumulation of foliar Fe to levels ranging from 59 to 196 ppm and prevented development of significant visual symptoms for all Cultivars.

`NuMex Centennial' and `NuMex Twilight' Ornamental Chiles

Table 1. Characteristics in millimeters of ‘NuMex Centennial’ and ‘NuMex Twilight’ grown in 0.35-liter Fig. 1. ‘NuMex Centennial’ (top) and ‘NuMex Twilight’ (bottom). New Mexico State Univ. Agricultural Expt. Station announces the release of ‘NuMex Centennial’ and ‘NuMex Twilight’, ornamental piquin chiles (Capsicum annuum L.) (Bosland, 1992). Fruit ripens from purple, to yellow, then to orange, and lastly to red. The various fruit colors enhance their value as commercial greenhouse pot plants. These cultivars likely will be accepted favorably by the pot plant industry. Unlike standard chile cultivars that have a dichotomous growth pattern, the polychotomous branching of the basal branches makes these new cultivars ideal for pot plant production.

490 PB 140 MARIGOLD GROWTH IN SOILLESS MEDIA AMENDED WITH PHOSPHORUS-CHARGED ALUMINA

Soilless growing media are used extensively in the greenhouse, especially for the potted plant production. Unlike soil having a phosphorus (P)-fixing ability, soilless media allows greater P leaching from the media. Leaching of excess P results in inefficient fertilizer utilization and effluent pollution. In hydroponic and sand-culture systems, alumina adsorbed with P (P-alumina) has been developed as a P source to maintain buffered P concentrations in nutrient solutions. This P-alumina has not been used with soilless media; however, it may have a potential of serving as a P source for plant growth and a P buffer to alleviate P leaching in soilless media. Marigolds were grown in soilless media (peat moss: vermiculite: sand=2:2:1, v/v/v) with P-alumina at various concentrations being substituted for sand. These marigolds were fertilized with a nutrient solution containing no additional P, while the control was fertilized with complete nutrient solution. In four cultivars of marigolds, me P-alumina treatments produced comparable or superior growth and floral production compared to plants provided with complete nutrient solutions or conventional fertilizer. 70% of applied P was leached in conventional treatments compared to only 2% in the P-alumina treatments.

Phytopathological aspects of closed irrigation systems

European and in particular German growers have to struggle with environmental programs, public concern, drastical decrease in the number of available pesticides and high costs for manpower and energy. Some of these problems may be solved by soilless cultivation and/or recirculating irrigation systems. For pot plant cultivation closed subirrigation systems (troughs, flooding benches) are widely used in European greenhouses. In Germany in an increasing extent also for the outdoor production of pot plants and woody container plants. As far as soilless cultivation is concerned open system are still predominant in cut flower and stock plant production. The hesitant introduction of soilless, closed irrigation systems may be due to high investments and growers fear of spreading diseases. A closed irrigation system is defined as one in which losses of water, nutrients and pesticides are widely avoided thus preventing pollution of soil or ground water. Depending on the path of water movement, recirculating irrigation systems can be classified as demonstrated in figure 1 (Molitor and Wohanka, 1992). Case A describes systems in which nutrient solution is applied to the top and drain water is collected after passing through the roots and the substrate, e. g. rockwool culture with trickle irrigation. Case B demonstrates subirrigation systems in which the nutrient solution is applied to the bottom and soaks up into the root zone while the rest of the nutrient solution remains in the circulating system, e. g. subirrigation with pot plants. Case C represents substrate free cultivation such as NFT, plant plane hydrponic or aeroponics in which the bare root system is continually in contact with the circulating solution. The risk of disease dispersal depends to great extent on the type of irrigation system and on the water movement is the root zone in particular.

Biological control of pests in Swedish pot plant production

Biological control of glasshouse pests is nowadays an important factor in the production of pot plants in Sweden. During 1990, more than 100 growers applied one or more methods of biocontrol, some only in propagation units but many during the entire production of several crops. Poinsettia is the major crop in this context. Eighty growers were interviewed about their experiences of various biocontrol methods. The use of Neoaplectana carpocapsae against sciarids and Otiorhynchus sulcurus was the most popular and reliable method. Next comes Encarsia formosa against whiteflies. Other methods include Verticillium lecanii against whiteflies and thrips, Aphidius matricariae against aphids, and predatory mites against thrips and spider mites.

LONG DAYS PROMOTE FLOWERING OF ARMERIA MARITIMA

Armeria maritima was studied to provide guidelines for flowering potted plant production. Seed and vegetatively propagated plants were exposed to 9-hr, 13-hr, or 17-hr photoperiods. Flowering was enhanced under the 13-hr and 17-hr photoperiods. Peduncle and leaf length were shorter, and plants were more compact under short days (SD, 9-hr photoperiod) than under long days (LD). When grown under SDs then moved at monthly intervals to LDs, the degree to which the compact growth habit (CH) was expressed was dependent upon the length of exposure to SDs. Plants with the CH produced fewer inflorescences than full growth habit plants. Plants held in cold storage (4C) flowered more profusely under LDs, but had a delay in flowering. There was more uniform flowering for plants held in cold storage than those held in a cool greenhouse (7C night temperature).

Stem elongation and flowering of the long-day plant Campanula isophylla Moretti in response to day and night temperature alternations and light quality

Stem elongation and plant height at flowering in Campanula isophylla Moretti were greater when plants were exposed to far red (FR) light or light from incandescent lamps which had a low red (R)/FR ratio (0.7). The difference in final stem length between FR- and R-light-treated plants was greatest when the light treatments were given during the entire night or as a 3 h end-of-day (EOD) lighting period. Only minor differences existed between R and FR light treatments when plants were given light in the middle of the night. However, FR light suppressed lateral branching compared with R light. The reduction in plant height as a result of a lower day temperature (DT) than night temperature (NT) was nullified by day-extension lighting with incandescent lamps. With fluorescent lamps (R/FR ratio 4.2), plant heightwas significantly less at 15/21°C (negative DT-NT (DIF)) than at 21/15°C DT/NT (positive DIF). Continuous lighting (CL) during the entire night or with 3 h night interrupttion (NI) treatments with R or FR light immediately after the middle of the night was equally effective at inducing flowering, and much more effective than EOD or end-of-night (EON) lighting. DIF had a slight influence on the rate of flower development, but negative DIF grown plants had 24% more flowers and flower buds, and 26% higher dry weight, than positive DIF plants. Practical applications of light quality and negative DIF treatments for the production of high-quality pot plants of C. isophylla are discussed.

THE ECONOMIC EFFECT OF AVERSION TO RISK DURING TACTICAL PLANNING IN POT PLANT PRODUCTION

Two risk avers strategies are applied during tactical planning in pot plant production. Production risk should be reduced by an extra optional week added to the cultivation-schedule and price risk should be reduced by a staggered selling-schedule. However, the effect of these risk avers strategies after a simulated implementation of tactical plans is limited. The first strategy results in a lower financial result. And with respect to the second strategy no significant difference can be proved. Therefore other approaches should be developed and attention should be directed to operational management. Futhermore, the present study shows the relation between the financial result and the efficiency of space utilization.

A crop growth simulation model for operational management support in pot plant production

A crop growth simulation model has been developed to support operational management in pot plant production. The model takes into account essential crop growth determining physiological processes and links up with prospective economic models. The time steps and the complexity of the crop growth model should be tuned to the economic models. The presented application of the model, specified for Schefflera arboricola ‘Compacta’, indicates that further economic research relating to this model could have a beneficial effect on operational management in pot plant production.

OPTIMIZING RESOURCE ALLOCATION FOR GREENHOUSE POTTED PLANT PRODUCTION

ABSTRACT A procedure for studying the profitability of greenhouse potted plant production systems subject to resource constraints was developed. The constrained condition and resources were the crop production schedule, greenhouse space, labor, and budget. A database containing the information for determining the required resources and operating costs for growing various crops was established. The database also provides the estimated revenue from sales of the crops, on a per pot basis. An algorithm was developed to determine first the feasibility of a given production plan and then determine the quantities of crops to be grown in order to yield an optimum profit. The result of this algorithm may serve to optimize allocation of resources for year-round production. The algorithm along with the crop database was incorporated into a user-friendly micro-computer program..