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Madeline W. Olberg and Roberto G. Lopez

Due to the high cost associated with constructing and operating a greenhouse, many growers have begun using alternative, low-input methods for bedding plant production, such as unheated high tunnel and outdoor production. Previous research indicates that bedding plant production in unheated high tunnels may be suitable for cold-tolerant species, but flowering is delayed compared with greenhouse production. To our knowledge, there has been no published research on the effects of outdoor production on bedding plant species. The objectives of this study were therefore to 1) compare the growth and development of 10 cold-tolerant and intermediate annual bedding plant species grown in an unheated high tunnel or in an unprotected outdoor growing area, 2) evaluate the effect of a 1-week acclimation period in the high tunnel before outdoor production, and 3) quantify the effectiveness of these production methods for producing high-quality bedding crops. Seedlings of ‘Antigua Orange’ african marigold (Tagetes erecta), ‘Hot Cakes White’ stock (Matthiola incana), and ‘Lilac Flame’ primula (Primula acaulis), and rooted cuttings of ‘Aloha Kona Hot Pink’ calibrachoa (Calibrachoa ×hybrida), ‘Royal Lavender’ regal geranium (Pelargonium ×domesticum), ‘Bella Oceano’ lobelia (Lobelia erinus), ‘Potunia Plus Red’ petunia (Petunia ×hybrida), ‘Phloxy Lady Purple’ phlox (Phlox maculata), ‘Summertime Pink Charme’ osteospermum (Osteospermum ecklonis), and ‘Empress Purple’ verbena (Verbena ×hybrida) were transplanted on 13 Apr. 2015 (week 16) into an unheated high tunnel or an outdoor growing area, or into an unheated high tunnel for a 1-week acclimation period before being moved outdoors. Average mean daily air temperature was 2.3 °C lower outdoors compared with inside the high tunnel, whereas average daily light integral (DLI) increased by 11.7 mol·m−2·d−1. All plants were delayed when grown outdoors compared with in the high tunnel, and all marigolds grown outdoors died in April when outdoor air temperatures dropped below −4 °C. When plants were acclimated for a 1-week period before outdoor production, all species, with the exception of regal geranium, were delayed by less than 1 week compared with those grown in the high tunnel. Stem length of all species grown outdoors was reduced or similar to those in the high tunnel, whereas biomass accumulation and branch number was unaffected or increased for most species. Overall, high-quality bedding plants could be grown outdoors, although development may be delayed compared with high tunnel production. Growers must be aware of the risk of crop loss due to extreme temperatures and plan for delays when growing annual bedding plant crops outdoors.

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Christopher J. Currey and Roberto G. Lopez

Total crop management (TCM) is a holistic approach to crop production that integrates data collection and interpretation to facilitate decisions that produce a uniform, high-quality, and marketable crop. Our objective was to determine if integrating TCM into poinsettia (Euphorbia pulcherrima) production experiences at two separate land-grant universities would improve student confidence in greenhouse potted plant production decision-making skills. Students produced containerized poinsettias and collected data on the greenhouse environment [light, temperature, and relative humidity (RH)], plant growth, media properties, irrigation water quality, and pest populations weekly at Purdue University (PU) (2011 and 2013) and Iowa State University (ISU) (2013) or biweekly (2015). Students were provided with self-assessments at the beginning and end of each course with statements about TCM and the various components comprising TCM activities. For nearly every statement at both institutions, self-assessments in confidence and understanding increased on the pre- to postsemester surveys. The systematic data collection combined with discussion and reflection provides an opportunity for peer instruction and learning. We believe TCM increases student confidence in their greenhouse plant production skills.

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W. Garrett Owen and Roberto G. Lopez

Under low-light greenhouse conditions, such as those found in northern latitudes, foliage of red leaf lettuce (Lactuca sativa L.) varieties is often green and not visually appealing to consumers. Our objective was to quantify the effect of end-of-production (EOP; prior to harvest) supplemental lighting (SL) of different sources and intensities on foliage color of four red leaf lettuce varieties, ‘Cherokee’, ‘Magenta’, ‘Ruby Sky’, and ‘Vulcan’. Plants were finished under greenhouse ambient solar light and provided with 16-hours of day-extension lighting from low intensity light-emitting diode (LED) lamps [7:11:33:49 blue:green:red:far red (control)] delivering 4.5 μmol·m−2·s−1, or 16-hours of EOP SL from high-pressure sodium (HPS) lamps delivering 70 μmol·m−2·s−1, or LED arrays [100:0, 0:100, or 50:50 (%) red:blue] delivering 100 μmol·m−2·s−1, or 0:100 blue LEDs delivering 25 or 50 μmol·m−2·s−1. Relative chlorophyll content (RCC) and foliage L* (lightness), and chromametric a* (change from green to red) and b* (change from yellow to blue) values were significantly influenced by EOP SL and days of exposure. Generally, RCC of all varieties increased from day 3 to 14 when provided with EOP SL from the HPS lamps and LEDs delivering 100 μmol·m−2·s−1. End-of-production SL providing 100 μmol·m−2·s−1 of 100:0, 0:100, or 50:50 red:blue light for ≥5 days resulted in increasing a* (red) and decreasing L* (darker foliage), b* (blue), and h° (hue angle; a measure of tone) for all varieties. Our data suggests that a minimum of 5 days of EOP SL providing 100 μmol·m−2·s−1 of 100:0, 0:100, or 50:50 red:blue light enhanced red pigmentation of ‘Cherokee’, ‘Magenta’, ‘Ruby Sky’, and ‘Vulcan’ leaves when plants are grown under a low greenhouse daily light integrals (DLIs) <10 mol·m−2·d−1.

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Ariana P. Torres and Roberto G. Lopez

Current market trends indicate an increasing demand for unique and exotic flowering crops, including tropical plants. Tecoma stans (L. Juss. Kunth) ‘Mayan Gold’ is a tropical plant that was selected as a potential new greenhouse crop for its physical appearance and drought and heat tolerance. However, in winter and early spring, when propagation occurs, outdoor photosynthetic daily light integral (DLI) can be relatively low. The objective of this study was to quantify the effects of DLI during propagation of Tecoma and to determine optimum DLI levels for seed propagation. Seeds were propagated under 13 mean DLIs ranging from 0.75 to 25.2 mol·m−2·d−1 created by the combination of high-pressure sodium lamps (HPS) and fixed woven shadecloths of varying densities. Thirty-five days after sowing, height, stem diameter, node number, relative leaf chlorophyll content, leaf fresh weight, leaf number, total leaf area, individual leaf area, leaf area ratio, shoot and root dry mass increased as DLI increased. Average internode elongation and specific leaf area decreased at a quadratic and linear rate, respectively, as DLI increased from 0.75 to 25.2 mol·m−2·d−1. These experiments indicate that high-quality Tecoma seedlings were obtained when DLI was 14 to 16 mol·m−2·d−1 during propagation.

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Ariana P. Torres and Roberto G. Lopez

Tecoma stans (L. Juss. Kunth) ‘Mayan Gold’ is a tropical flowering plant that was selected as a potential new greenhouse crop for its physical appearance and drought and heat tolerance. The objective of this study was to quantify how temperature during the finishing stage and photoperiod during propagation and finishing stages influence growth, flowering, and quality. In Expt. 1, plants were propagated from seed under four photoperiods (9, 12, 14, or 16 h) for 35 days. Under long-day (LD) photoperiods (14 h or greater), seedlings were 3.0 to 3.7 cm taller than those propagated under 9-h photoperiods. During the finishing stage, days to first open flower, shoot dry mass, and number of nodes below the terminal inflorescence were reduced when plants were grown under LD photoperiods. In addition, number of open flowers and branches increased under LD photoperiods. Few plants developed visible buds when grown under short-day (SD) photoperiods (12 h or less). In Expt. 2, plants were forced at average daily temperatures of 19, 20, or 22 °C after transplant. Time to first open flower was reduced by 7 days as temperature increased. Inversely, number of visible buds increased by 57 as temperature increased from 19 to 22 °C. Under the experimental conditions tested, the most rapid, complete, and uniform flowering of Tecoma occurred when plants were propagated and finished under LD photoperiods and forced at 22 °C.

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Annika E. Kohler and Roberto G. Lopez

Domestic production of culinary herbs continues to increase in the United States. Culinary herbs are primarily propagated by seed; however, some herbs have poor germination rates and slow growth. Thus, there are advantages of propagating herbs by vegetative stem-tip cuttings as they lead to true-to-type plants and a shortened production time. Previous research of ornamental young plants and finished culinary herbs have shown a reduction in rooting time and increases in plant quality with increases in the photosynthetic daily light integral (DLI). To our knowledge, little to no research has addressed how the DLI influences culinary herb liner quality. Therefore, the objectives of this study were to quantify morphological traits of five economically important culinary herbs when grown under DLIs ranging from 2.8 to 16.4 mol·m−2·d−1. Stem-tip cuttings of Greek oregano (Origanum vulgare var. hirtum), rosemary ‘Arp’ (Rosmarinus officinalis), sage ‘Extrakta’ (Salvia officinalis), spearmint ‘Spanish’ (Mentha spicata), and thyme ‘German Winter’ (Thymus vulgaris) were excised from stock plants and rooted under no shade or aluminum shading of 36%, 56%, or 76% to create a range of DLI treatments. After 9 days (spearmint) or 16 days (all other genera) of DLI treatments, the root, shoot, and total dry mass of all culinary herb liners generally increased by 105% to 449%, 52% to 142%, and 82% to 170%, respectively, as the DLI increased from 2.8 to 16.4 mol·m−2·d−1 or genus-specific DLI optimums. Stem length of oregano, spearmint, and thyme decreased by 37%, 28%, and 27%, respectively, as the DLI increased from 2.8 to 16.4 mol·m−2·d−1. However, stem length of rosemary and sage were unaffected by the DLI. The quality index of all genera was greatest at DLIs from 10.4 to 16.4 mol·m−2·d−1. Furthermore, all culinary herbs grown under a DLI of ≤6 mol·m−2·d−1 had low root and shoot dry mass accumulation; and oregano, spearmint, and thyme were generally taller. Therefore, DLIs between 10 to 12 mol·m−2·d−1 should be maintained during culinary herb propagation, because a DLI ≥16 mol·m−2·d−1 may be deleterious and energy inefficient if supplemental lighting use is increased.

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Allison Hurt, Roberto G. Lopez, and Joshua K. Craver

In northern latitudes, the photosynthetic daily light integral can be less than 5 mol·m–2·d–1, necessitating the use of supplemental lighting (SL) to reduce bedding plant seedling production time and increase quality. Our objectives were 1) to quantify seedling quality and production time under continuous 16-h or instantaneous threshold SL, continuous low-intensity photoperiodic lighting (PL) for 16 or 24 hours with and without far-red light, or no electric lighting; and 2) to determine whether the described lighting treatments during propagation impact finished plant quality or flowering. Seeds of begonia (Begonia ×semperflorens) ‘Bada Bing Scarlet’, gerbera (Gerbera jamesonii) ‘Jaguar Deep Orange’, impatiens (Impatiens walleriana) ‘Accent Premium Salmon’, petunia (Petunia ×hybrida) ‘Ramblin Peach Glo’, and tuberous begonia (Begonia ×tuberosa) ‘Nonstop Rose Petticoat’ were sown in 128-cell trays and grown under either SL, PL, or no electric lighting (control). SL treatments consisted of high-intensity light-emitting diode (LED) or high-pressure sodium (HPS) lamps providing a photosynthetic photon flux density (PPFD) of either 70 µmol·m–2·s–1 on continuously for 16 h·d–1 or 90 µmol·m–2·s–1 based on an instantaneous threshold. PL treatments consisted of low-intensity red:white (R:W) or red:white:far-red (R:W:FR) lamps for 16 h·d–1 or R:W:FR lamps for 24 h·d–1. Seedlings of gerbera, impatiens, and petunia from each treatment were subsequently transplanted and finished in a common greenhouse environment. The highest quality seedlings were grown under SL compared with PL or control conditions. When comparing SL treatments, seedlings produced under HPS or LED SL using an instantaneous threshold were of equal or greater quality compared with those under continuous SL with a 16-h photoperiod. Although the greater leaf area and internode elongation under PL may give growers the perception that seedling production time is reduced, PL did not increase biomass accumulation and seedling quality. Petunia seedlings propagated under HPS lamps using an instantaneous threshold flowered 4 to 11 days earlier compared with the other SL treatments. In addition, petunia propagated under R:W:FR PL for 16 h·d–1 flowered 5 to 7 days earlier compared with LED SL and the other PL treatments.

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Michael A. Ortiz, Krystyna Hyrczyk, and Roberto G. Lopez

The U.S. specialty cut flower market has grown over the last several years because stems of many specialty cut flower species cannot be transported long distances and therefore need to be grown regionally. High tunnel production of cut flowers is an alternative to field and greenhouse production that has several benefits. Specialty cut flower species Antirrhinum majus L. ‘Potomac Orange’ and ‘Rocket Red’, Celosia argentea L. var. cristata Kuntze ‘Chief Red’, Dahlia ×hybrida Cav. ‘Karma Thalia Dark Fuchsia’, Dianthus barbatus L. ‘Amazon Neon Cherry’, Eustoma russellianum Salisb. ‘Mariachi Blue’, Helianthus annuus L. ‘Premier Lemon’ and ‘Sunrich Yellow’, Matthiola incana (L.) W.T. Aiton ‘Katz Lavender Blue’, and Zinnia elegans Jacq. ‘Benary Giant Scarlet’ were grown in both field and high tunnel environments in the midwestern United States. High tunnel production resulted in a first week’s harvest of 44.8 (46%), 115, and 21.1 (110%) more stems for Antirrhinum ‘Rocket Red’, Dianthus, and Zinnia, respectively. Compared with field production, high tunnel production yielded a greater number of stems/m2 for Antirrhinum ‘Potomac Orange’, Celosia, Dianthus, and Zinnia and longer stems for Antirrhinum ‘Potomac Orange’ and ‘Rocket’, Eustoma, Matthiola, and Zinnia. For example, high tunnel production yielded 185 (39%) and 192 (59%) more stems/m2 and 12.6 (34%) and 8.9 (32%) cm longer stems for Mathiola and Zinnia, respectively. Other stem characteristics such as inflorescence length and flower width showed more variation among cultivars. Our results indicate that cut flower yield and/or quality of Antirrhinum ‘Rocket Red’, Dianthus, Matthiola, Zinnia, Dahlia, Eustoma, and Helianthus ‘Sunrich Yellow’ and ‘Premier Lemon’ significantly increases when produced in high tunnels located in the Midwest.

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Joshua K. Craver, Jennifer K. Boldt, and Roberto G. Lopez

Previous research has shown high-quality annual bedding plant seedlings can be produced in controlled environments using light-emitting diode (LED) sole-source lighting (SSL). However, when only red and blue radiation are used, a delay in time to flower may be present when seedlings of some long-day species are subsequently finished in a greenhouse. Thus, our objective was to evaluate the effects of various radiation qualities and intensities under SSL on the morphology, nutrient uptake, and subsequent flowering of annual bedding plant seedlings with a long-day photoperiodic response. Coreopsis (Coreopsis grandiflora ‘Sunfire’), pansy (Viola ×wittrockiana ‘Matrix Yellow’), and petunia (Petunia ×hybrida ‘Purple Wave’) seedlings were grown at radiation intensities of 105, 210, or 315 µmol·m−2·s−1, achieved from LED arrays with radiation ratios (%) of red:blue 87:13 (R87:B13), red:far-red:blue 84:7:9 (R84:FR7:B9), or red:green:blue 74:18:8 (R74:G18:B8). Four-week-old seedlings were subsequently transplanted and grown in a common greenhouse environment. Stem caliper, root dry mass, and shoot dry mass of seedlings generally increased for all three species as the radiation intensity increased from 105 to 315 µmol·m−2·s−1, regardless of radiation quality. Similarly, stem length of all three species was generally shorter as the radiation intensity increased. Macro- and micronutrient concentrations were also generally lower as the radiation intensity increased for all three species. Pansy seedlings grown under R84:FR7:B9 flowered an average of 7 and 5 days earlier than those under R87:B13 and R74:G18:B8, respectively. These results provide information regarding the specific radiation parameters from commercially available LEDs necessary to produce high-quality seedlings under SSL, with radiation intensity appearing to be the dominant factor in determining seedling quality. Furthermore, the addition of far-red radiation can reduce time to flower after transplant and allow for a faster greenhouse turnover of some species with a long-day photoperiodic response.

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Joshua R. Gerovac, Roberto G. Lopez, and Neil S. Mattson

Commercial bedding plant production in northern latitudes often begins in late winter and continues through spring, when average outdoor temperatures require growers to actively heat their greenhouses (GHs). High tunnels (HTs) offer energy savings as they are passively heated and cooled structures that have a low initial cost. As a result, they have been used in northern latitudes to advance and extend the growing season and improve the quality of high-value horticultural crops. However, there is limited published information on growing bedding plants in HTs in northern latitudes. Our objectives were to quantify the effects of transplant date in an HT with or without a rowcover (RC) compared with a traditional heated GH on the growth and morphology of three cold-tolerant bedding plant species at two northern latitude locations, Purdue University (Purdue) and Cornell University (Cornell). Seedlings of snapdragon (Antirrhinum majus L. ‘Liberty Classic Yellow’), dianthus (Dianthus chinensis L. ‘Telstar Crimson’), and petunia (Petunia ×hybrida Vilm.-Andr. ‘Wave Pink’) were transplanted on weeks 13, 14, and 15 in 2012 (Purdue) and 2013 (both locations) and moved to either a glass-glazed GH or an HT without (HT) or with a rowcover (HT+RC). Several quality measurements increased when plants were grown in the HT compared with those grown in the GH. Dianthus and petunia transplanted at Purdue during week 13 in the HT and HT+RC were 33% and 47% shorter and had 51% and 31% more visible buds, respectively, compared with those grown in the GH. Similarly, petunia transplanted at Cornell during week 13 in the HT and HT+RC were 45% and 43% shorter, respectively, than their GH counterparts. The shoot dry mass of dianthus and snapdragon at Purdue was significantly higher when grown in the HT compared with the GH, regardless of transplant week or the use of RC likely because of increased daily light integral (DLI) in the HT environment. There was about a 1-week delay from transplant to first open flower for week 13 dianthus (at Purdue) and petunia (at both locations) when finished in the HT or HT+RC vs. their GH counterparts. Such a delay would be acceptable to growers who want to reduce the use of chemical growth regulators and heating costs. However, at both locations snapdragon transplanted on week 13 to the HT or HT+RC environments were delayed by 22 to 26 days compared with the GH. A delay of over 3 weeks could interfere with a grower’s production schedule, possibly making this crop unsuitable for production in northern latitude HTs.