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W. Garrett Owen and Roberto G. Lopez

Crown division, tissue culture, and culm cuttings are methods for propagating purple fountain grass [Pennisetum ×advena Wipff and Veldkamp (formerly known as Pennisetum setaceum Forsk. Chiov. ‘Rubrum’)]. However, propagation by culm cuttings is becoming an economically attractive method for quick liner production. Our objective was to quantify the impact of propagation daily light integral (PDLI) and root-zone temperature (RZT) on root and culm development of single-internode purple fountain grass culm cuttings. Before insertion into the rooting substrate, cuttings were treated with a basal rooting hormone solution containing 1000 mg·L−1 indole-3-butyric acid (IBA) + 500 mg·L−1 1-naphthaleneacetic acid (NAA). The cuttings were placed in a glass-glazed greenhouse with an air temperature of 23 °C and benches with RZT set points of 21, 23, 25, or 27 °C. PDLIs of 4 and 10 mol·m−2·d−1 (Expt. 1) or 8 and 16 mol·m−2·d−1 (Expt. 2) were provided. After 28 d, culm and root densities (number) increased as the RZT increased from 21 to 27 °C, regardless of PDLI during Expt. 1. Compared with 4 mol·m−2·d−1, a PDLI of 10 mol·m−2·d−1 generally resulted in the greatest root biomass accumulation. For example, as PDLI increased from 4 to 10 mol·m−2·d−1, root dry mass increased by 105%, 152%, and 183% at RZTs of 21, 25, and 27 °C, respectively. In Expt. 2, as the RZT increased from 21 to 23 °C, root dry mass increased by 70% under a PDLI of 8 mol·m−2·d−1. However, root dry mass was similar among all RZTs under a PDLI of 16 mol·m−2·d−1. Our results indicate that single-internode culm cuttings of purple fountain grass can be most efficiently propagated under PDLIs of 8–10 mol·m−2·d−1 together with RZT set points of 23 to 25 °C for quick liner production.

Free access

Roberto G. Lopez and Erik S. Runkle

The vegetatively propagated `Fire Kiss' clone of the hybrid Zygopetalum Redvale orchid has appealing potted-plant characteristics, including fragrant flowers that are waxy lime-green and dark maroon with a broad, three-lobed, magenta and white labellum. We performed experiments to quantify how temperature influenced leaf unfolding and expansion, time from visible inflorescence to flower, and longevity of individual flowers and inflorescences. Plants were grown in controlled-environment chambers with constant temperature set points of 14, 17, 20, 23, 26, and 29 °C and an irradiance of 150 μmol·m-2·s-1 for 9 h·d-1. As actual temperature increased from 14 to 25 °C, the time to produce one leaf decreased from 46 to 19 days. Individual plants were also transferred from a greenhouse to the chambers on the date that an inflorescence was first visible or the first flower of an inflorescence opened. Time from visible inflorescence to open flower decreased from 73 days at 14 °C to 30 days at 26 °C. As temperature increased from 14 to 29 °C, flower and inflorescence longevity decreased from 37 and 38 days to 13 and 15 days, respectively. Data were converted to rates, and thermal time models were developed to predict time to flower and senescence at different temperatures. The base temperature was estimated at 6.2 °C for leaf unfolding, 3.5 °C for time to flower, and 3.7 °C for flower longevity. These models could be used by greenhouse growers to more accurately schedule Zygopetalum flowering crops for particular market dates.

Free access

W. Garrett Owen and Roberto G. Lopez

Under low-light greenhouse conditions, anthocyanin pigmentation in vegetative tissues of red- or purple-leafed floricultural crops is not fully expressed and, consequently, plants are not as visually appealing to consumers. Our objective was to quantify the effect of end-of-production (EOP; before shipping) supplemental lighting (SL) of different light sources, qualities, and intensities on foliage color of geranium (Pelargonium ×hortorum L.H. Bailey ‘Black Velvet’) and purple fountain grass [Pennisetum ×advena Wipff and Veldkamp (formerly known as Pennisetum setaceum Forsk. Chiov. ‘Rubrum’)]. Plants were finished under early (Expt. 1) and late (Expt. 2) seasonal 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 light ratio (%); 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, 87:13, 50:50, or 0:100 red:blue) delivering 100 μmol·m−2·s−1, or 0:100 red:blue LEDs delivering 25 or 50 μmol·m−2·s−1. Geranium and fountain grass chlorophyll content and leaf color were estimated using a SPAD-502 chlorophyll meter and Minolta tristimulus colorimeter, respectively. Relative chlorophyll content (RCC) and foliage L* (lightness), C* (chroma; a measure of saturation), and h° (hue angle; a measure of tone) values were significantly influenced by EOP SL and days of exposure. Generally, RCC of geranium and fountain grass increased from 3 to 14 days of exposure to EOP SL from HPS lamps and LEDs delivering 100 μmol·m−2·s−1. Under low daily light integrals (DLIs) [8.6 mol·m−2·d−1 (geranium) and 9.4 mol·m−2·d−1 (purple fountain grass)] EOP SL providing 100 μmol·m−2·s−1 of 100:0, 87:13, 50:50, or 0:100 red:blue light for ≥14 days resulted in lower L* (darker foliage), C* (saturated), and h° (orange to violet-red hues). Our data indicate that a minimum of 14 days of EOP SL providing 100 μmol·m−2·s−1 of 50:50 or 0:100 red:blue light enhanced foliage color of geranium and fountain grass leaves when plants were grown under a low greenhouse DLI ≤ 9 mol·m−2·d−1.

Free access

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.

Open access

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.

Free access

Christopher J. Currey and Roberto G. Lopez

Increasing photosynthetic daily light integral (DLI) by supplementing with high-pressure sodium (HPS) lamps during propagation has been shown to enhance photosynthesis and biomass accumulation of cuttings. The development of high-intensity light-emitting diodes (LEDs) is a promising technology with potential as a greenhouse supplemental lighting source. Our objective was to quantify the impact of narrow spectra supplemental lighting from LEDs on growth, morphology, and gas exchange of cuttings compared with traditional HPS supplemental lighting. Cuttings of Impatiens hawkeri W. Bull ‘Celebrette Frost’, Pelargonium ×hortorum L.H. Bailey ‘Designer Bright Red’, and Petunia ×hybrida Vilm. ‘Suncatcher Midnight Blue’ were received from a commercial propagator and propagated in a glass-glazed greenhouse at 23 °C air and substrate temperature set points. After callusing (≈5 mol·m−2·d−1 for 7 days), cuttings were placed under 70 μmol·m−2·s−1 delivered from HPS lamps or LED arrays with varying proportions (%) of red:blue light (100:0, 85:15, or 70:30). After 14 days under supplemental lighting treatments, growth, morphology, and gas exchange of rooted cuttings were measured. There were no significant differences among Impatiens and Pelargonium cuttings grown under different supplemental light sources. However, compared with cuttings propagated under HPS lamps, stem length of Petunia cuttings grown under 100:0 red:blue LEDs was 11% shorter, whereas leaf dry mass, root dry mass, root mass ratios, and root:shoot ratio of cuttings grown under 70:30 red:blue LEDs were 15%, 36%, 17%, and 24% higher, respectively. Supplemental light source had minimal impact on plants after transplant. Our data suggest that LEDs are suitable replacements for HPS lamps as supplemental light sources during cutting propagation.

Full access

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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Christopher J. Currey and Roberto G. Lopez

The influence of pre-plant bulb dips in paclobutrazol solutions on final plant height, days to flower, and flower bud number were evaluated for easter lily (Lilium longiflorum). ‘Nellie White’ easter lily bulbs were placed in solutions of paclobutrazol containing 0, 30, 60, or 120 mg·L−1 for 15 min preceding planting. Days to flower and flower bud number were unaffected by paclobutrazol. Plant height at flowering for bulbs dipped in paclobutrazol solutions was 15% to 26% shorter compared with untreated bulbs. Additionally, dipping bulbs in 120 mg·L−1 paclobutrazol resulted in plants that met target height specifications for commercially grown easter lily. Based on these results, dipping easter lily bulbs in paclobutrazol solutions can be an effective strategy for reducing stem elongation without negatively impacting days to flower or flower bud number for commercially grown easter lily.

Free access

Roberto G. Lopez and Erik S. Runkle

A majority of commercial propagation of herbaceous ornamental cuttings occurs during the winter when the photosynthetic daily light integral (DLI) is relatively low. We quantified how the mean DLI influenced rooting and subsequent growth and development of two popular vegetatively propagated species, New Guinea impatiens (Impatiens hawkeri Bull.) and petunia (Petunia ×hybrida hort. Vilm.-Andr.). Three cultivars of each species were propagated under a mean DLI ranging from 1.2 to 10.7 mol·m−2·d−1. Cuttings were rooted in a controlled greenhouse environment maintained at 24 to 25 °C with overhead mist, a vapor-pressure deficit of 0.3 kPa, and a 12-h photoperiod. Rooting and growth evaluations of cuttings were made after 8 to 16 d. In a separate experiment, rooted cuttings under DLI treatments were then transplanted into 10-cm containers and grown in a common greenhouse at 21 ± 2 °C under a 16-h photoperiod to identify any residual effects on subsequent growth and development. In both species, rooting, biomass accumulation, and quality of cuttings increased and subsequent time to flower generally decreased as mean propagation DLI increased. For example, root number of petunia ‘Tiny Tunia Violet Ice’ after 16 days of propagation increased from 17 to 40 as the propagation DLI increased from 1.2 to 7.5 mol·m−2·d−1. In addition, cutting shoot height decreased from 6.3 to 4.5 cm, and root and shoot dry biomass of cuttings harvested after 16 days of propagation increased by 737% and 106%, respectively. Subsequent time to flower for ‘Tiny Tunia Violet Ice’ from the beginning of propagation decreased from 50 to 29 days as propagation DLI increased from 1.4 to 10.7 mol·m−2·d−1 regardless of the DLI provided after propagation. In New Guinea impatiens ‘Harmony White’, root and shoot dry weight of cuttings increased by 1038% and 82%, respectively, and subsequent time to flower decreased from 85 to 70 days as the propagation DLI increased from 1.2 to 10.7 mol·m−2·d−1. These experiments quantify the role of the photosynthetic DLI during propagation on the rooting and subsequent growth and development of vegetatively propagated herbaceous ornamental cuttings.

Full access

Roberto G. Lopez and Diane M. Camberato

Biodegradable, compostable, and traditional plastic containers were evaluated for production of ‘Eckespoint Classic Red’ poinsettia (Euphorbia pulcherrima), a long-term greenhouse crop (12–16 weeks transplant to finish, depending on cultivar). Containers were rated for appearance and durability during the 14-week production period and plant quality parameters were measured at anthesis. Plastic, rice hull, wheat starch-derived bioresin, and molded fiber containers remained unchanged in appearance and integrity and received a rating of 5 (1–5 rating scale, where 1 = container integrity compromised substantially and 5 = container was intact, no visible changes in terms of color or construction). However, straw, coconut coir, composted cow manure, and Canadian sphagnum moss and wood pulp containers had an average rating of 2.9, 2.7, 1.4, and 1.6, respectively. Both shoot and root dry weights were greatest in plants produced in molded fiber and straw containers. The root to shoot dry weight ratio and days to anthesis was not significantly different among container types. Bract area index (a measurement derived to estimate bract area) was greatest for plants produced in molded fiber containers and lowest for those produced in the wheat starch containers. When adjusted for container height, final plant height was greatest in molded fiber containers and lowest in wheat starch containers. Plants produced in molded fiber containers, on average, exhibited the greatest height, bract area index, and total root and shoot weight, with no visible changes to container integrity. Based on these results, plant quality was not negatively impacted by any of the seven containers, though marketability of finished plants can be affected by container integrity.