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Open access

Joe J. Hanan

Abstract

Rosa hybrida L. cvs. Forever Yours and Cara Mia, were subjected to split night temperatures from November 1, 1977 to February 8-18, 1978. During the 22 weeks of treatment, split temperatures seriously delayed production and markedly reduced quality. Split temperatures for roses as a means of energy conservation did not appear to be a viable practice. Following the experiment, however, for a 9 week period, after returning night temperatures to 16.7°C, plants in the lowest temperature treatment produced twice as many flowers as compared to the entire previous record with a significant increase in quality and marked increase in bottom shoots. The effect appeared to be cumulative and suggested an inexpensive means for rejuvenating old rose plants.

Free access

Kristin L. Getter and D. Bradley Rowe

As forests, agricultural fields, and suburban and urban lands are replaced with impervious surfaces resulting from development, the necessity to recover green space is becoming increasingly critical to maintain environmental quality. Vegetated or green roofs are one potential remedy for this problem. Establishing plant material on rooftops provides numerous ecological and economic benefits, including stormwater management, energy conservation, mitigation of the urban heat island effect, and increased longevity of roofing membranes, as well as providing a more aesthetically pleasing environment in which to work and live. Furthermore, the construction and maintenance of green roofs provide business opportunities for nurseries, landscape contractors, irrigation specialists, and other green industry members while addressing the issues of environmental stewardship. This paper is a review of current knowledge regarding the benefits of green roofs, plant selection and culture, and barriers to their acceptance in the United States. Because of building weight restrictions and costs, shallow-substrate extensive roofs are much more common than deeper intensive roofs. Therefore, the focus of this review is primarily on extensive green roofs.

Open access

William B. Miller and R.W. Langhans

Abstract

The feasibility of utilizing different patterns of air temperature changes over the light and dark periods was investigated to provide a basis for greenhouse energy conservation. ‘Grand Rapids’ lettuce was grown hydroponically in microprocessor controlled growth chambers, under a light level of 325 µmol s-1m-2 PPF. Air temperatures were: a) increased from 15° to 35°C (late-peak), b) decreased from 35° to 15° (early-peak), and c) increased to 35°, then back to 25° (mid-peak) during the 16-hr light period. The late and mid-peak patterns had a gradual decrease in night air temperature, whereas the early peak pattern had a gradual increase in night air temperature. Each of these patterns averaged 25° during the light period, and 20° during the dark period. “Early-peak” plants grew poorly, whereas plants grown under the mid- and late-peak regimes grew well. Early morning diffusive resistance was similar for early- and mid-peak plants. Transpiration rates followed the air temperature changes.

Open access

J. N. Walker and J. W. Buxton

Abstract

An analysis of using an air-earth heat exchange for controlling the environment in a greenhouse was conducted. For purpose of the analysis, a small greenhouse (2.75 m wide and 4.25 m long) connected to 30.5 m of 45 cm diameter pipe was assumed. In terms of heating, the air-earth heat exchanges proved to be inadequate except for the very southern parts of the United States, and even in these locations the temperature had to be limited to a relatively cool temperature of 10°C. A similar analysis for summer showed that the air-earth heat exchange could effectively limit the occurrence of high temperatures in a greenhouse throughout the United States.

Open access

K. T. Huang and Joe J. Hanan

Abstract

The benefits of an internal cover between a greenhouse roof and the crop, or a cover over the outside of a greenhouse, were developed on a theoretical basis. The analysis indicated that heat savings by the use of an internal shade will be the same on clear or cloudy nights, with the main effect resulting from lower convective losses. Therefore, an internal cover can be inexpensive as long as it reduces convective heat losses. An external cover can reduce thermal radiation losses from the greenhouse roof, and in this case, the emissivity of an external cover should be as low as possible. Radiation properties do not depend upon color. Calculations indicate that heat savings of internal and external covers are about the same under conditions of clear, winter nights. The potential savings with either cover alone approaches 30% of the present average greenhouse heat requirements.

Open access

Carl E. Whitcomb

Abstract

A self-contained solar-heated greenhouse was devised consisting of a quonset structure covered with 3 layers of polyethylene which serves as a solar collector. Water mist circulates between the inner 2 poly layers and the heated water is stored in a sand bed in the floor.

Full access

Richard H. Merritt and K.C. Ting

A phase change material (PCM) energy storage unit operating in a greenhouse from 29 Oct. through 21 Dec. 1992 cooled it on the average 1.7C in the day and warmed it 2.2C at night due to both sensible and latent heat absorbed, released, and circulated. Tagetes patula `Mighty Marietta' and `Early Queen Sophia' marigolds and Viola × Wittrockiana `Yellow Blotch' and `Blue Blotch' pansies were grown in a PCM and a control (no PCM) greenhouse. Temperatures went below 0C 10 days in the control greenhouse and 4 days in the PCM greenhouse. The lowest temperature of -7.8C killed the marigolds in the control greenhouse. Neither marigolds nor pansies were killed in the PCM greenhouse, which attained a low temperature of -3.3C. On 4 Dec., plants were destructively harvested. Morphologically the marigolds were taller, and had more leaf area and dry matter when grown in the PCM greenhouse as compared to the control, but pansies were taller, and had more leaf area and dry matter when grown in the control greenhouse, as compared to the PCM greenhouse.

Open access

John W. White and John A. Biernbaum

Abstract

A crop of Calceolaria herbeohybrida Voss, was grown from December 1979 through March 1980 using a 16-week production schedule and nightbreak lighting to accelerate flowering. A second crop was grown from March through June 1980 without lighting. Root-zone heating of 20° to 22°C increased shoot fresh and dry weights and flower number but had no effect on days to anthesis. Plants at ambient (10° to 12°) root-zone temperature were of poor quality and underdeveloped; while plants with root-zone heating were well-developed with an adequate number of flowers. Root-zone heating was less effective for the March to June crop.

Open access

Adolph J. Laiche Jr.

Abstract

Southern-grown bulbs of ‘Ace’, ‘Croft’, ‘Harson’, and ‘Nellie White’ Easter lily were naturally cooled and greenhouse-forced with either constant minimum thermostat settings of 16.7 to 15.6°C or with thermostat settings lowered to 7.8 to 4.4° for 8 hours during the night to obtain a dual minimum night temperature regime. The actual greenhouse temperatures varied with outdoor temperatures. Average minimum temperatures obtained with constant and dual thermostat settings were 17.0 to 15.4° and 10.7 to 9.9°, respectively. With constant minimum temperature, 20 to 22 days less time was required to force ‘Harson’ as compared to ‘Ace’, ‘Croft’, and ‘Nellie White’. Dual night temperatures delayed flowering of the cultivars tested 9 to 13 days with a slight increase in flower number and a substantial increase in stem height. Although forcing time was increased with dual minimum temperatures, about 50% reduction in fuel usage was obtained.

Open access

Amr A.Ismail and David E.Yarborough

Abstract

No differences in plant stand, stem length, growth habit, flower bud formation or yield were detected between fall vs. spring or between mechanical vs. thermal pruning (burning with oil) of lowbush blueberries Vaccinium angustifolium Ait. This suggests that close flail mowing may be an acceptable alternative to burning for pruning lowbush blueberries.