Energy-Efficient Bedding Plant Production

Energy-EfficientBedding Plant ProductionErik RunkleProfessor of Horticulture

Energy prices are increasing

Overview: Greenhouse energy-saving tips

• Use infrared anti-condensate polyethylene film• Reduce air leaks / add insulation• Utilize and maintain horizontal air flow fans• Install/operate retractable energy/shade curtains at night• Start with larger transplants grown under high light• Use efficient photoperiodic lighting when growing long-day

annuals• Provide efficient, high-intensity lighting when growing young

plants• Temperature, crop timing, and energy consumption of annuals

Use infrared anti-condensate polyethylene film

• Some films block some of the Infra-red (IR, or heat) radiation.

• A double-poly covering with an IR film as the inside layerreduces heat loss during the night, which reduces heatingrequirements

• A Minnesota study estimated that the return on investment forinstalling an IR double poly plastic was less than 2 months,even when production was seasonal.

Reduce air leaks / add insulation

• Closely inspect the greenhouse glazing, walls, doors, fans,vents and other areas.

• Pay special attention to where the covering material attachesto the foundation, side and walls, and around fans and vents.

• Patch holes in the plastic covering and side walls, or replacecracked or missing glass panes

• Weather-strip doors, vents and fan openings

• Ensure louvers are sufficiently lubricated so that they closetightly

• Shut off some of your exhaust fans from late fall throughearly spring; then cover openings with insulation orplastic to reduce air infiltration

• If you have a double polygreenhouse, it is important thatthe space between the twolayers is properly inflated. Alwaysuse outside air to inflate the twolayers of plastic film.

Reduce air leaks / add insulation

AmericanHort Finished Plant Conference October 12, 2021

Erik Runkle, Michigan State University Page 1

Utilize and maintain horizontal air flow fans

• Horizontal airflow fans (HAFs) are installed in greenhouses to mix the air vertically and horizontally.

• Poor air uniformity results in non-uniform plant growth and development. Risks are elevated during winter, when little or no ventilation is used.

Guidelines for HAFs

• HAFs are typically installed in so-called “raceways” and direct the air in horizontal jets

• The recommended fan capacity is approximately 3 ft3 perminute per ft2 of growing area

• HAFs are typically mounted just below the trusses, but high enough to keep them out of the way for people and equipment

Utilize retractable energy/shade curtains

• Growers have reported seasonal energy savings of up to 30% with the use of a well-maintained energy curtain

• Generally, a computer system is required to automatically control the curtains

• Install stationary skirts around the outer edges of the curtains to prevent unwanted openings

• Shade/energy curtains are commonly made of a woven material containing aluminum strips, and can be of open or closed (using transparent plastic strips) design

Curtain materials

• The aluminum strips efficiently reflect radiation with minimal absorption

• Open strips: shade screen

• Closed strips: energy curtain

Energy curtains (thermal blankets) reduce plant heat loss at night by creating a warmer surface above the greenhouse crop. Thus, more radiant energy is emitted to the crop than a cold glazing material.

30 °F

64F60 °F

65 °F 65 °F

“Hidden” benefit of retractable curtains Factors that can influence production time and energy costs

• Plug/liner size and environment• Day length (photoperiod)• Light quantity (daily light integral)• Temperature management



Snapdragon ‘Rocket Mix’

Day

s to

flow

er

0

10

20

3040

506070

63 73Average daily temperature (°F)

–8days

288 plug128 plug

–7days

Use larger transplants grown under high light Petunia ‘Madness Red’

= Low-intensity lighting (3 μ –2 –1)= High-intensity lighting (90 μ –2 –1)

27 days after seed sow at 68 °F

Each or represents 9 days

The greatest value of supplemental lighting of plugs and liners is during the later production stages

Supplemental lighting during propagation can accelerate flowering

Petunia ‘Madness Red’7-11 –2 –1

044

48

52

56

60

64

cc

abababc

a

Days to flower with stages of supplemental lighting

11-16 –2 –1

044

48

52

56

60

64

dbcd

aabcab

cd

a

Use LEDs to deliver long-day lighting

Philipss GreenPowerr LEDPhilipss GreenPoweG r EDLFlowering DR/W/FR Lamp

Total Grow Night & Day Total Grow Night & DayManagement Lamp

Cosmos ‘Sonata Pink’Short Days Long Days

29 days to flower 65 days to flower

Example of facultative short-day plant

Petunia ‘Fantasy Pink Morn’Short Days Long Days

61 days to flower 34 days to flower

Example of facultative long-day plant



Rudbeckia ‘Indian Summer’Short Days Long Days

Example of obligate long-day plant

Short-day plantsAgeratumAfrican daisyBlue salviaCalendulaDianthusFuchsia (most)Mexican sunflower PansyPetunia (most)SalviaSnapdragonStaticeSunflowerVerbena

Bachelor’s buttonsBlue lobeliaChina asterFuchsia (some)GazaniaLobeliaMonkey flowerNierembergiaPetunia (some: Wave)RudbeckiaStrawflowerSweet peaTuberous begonia

Facultative ObligateLong-day plants

African marigoldCelosiaCosmosDahliaGomphrenaMina vineMoon flowerMorning glorySalviaSignet marigoldZinnia

Common Bedding Plant Responses to Photoperiod

Petunia ‘Wave Purple Classic’After 6 weeks at 68 F, -2 -1

Incandescent9-h day with 4-h night interruption from:

R+W LEDs R+W+FR LEDsNone

(control)

Photoperiodic lamps that work

Lamp type Short-day plants

Long-day plantsLow DLI High DLI

IncandescentFluorescent / XMix incandescent + CFLHID (HPS, MH)White LEDs / XRed LEDs / XRed + far-red LEDs

General efficacy of different lamp types at regulating flowering. = Effective; X = Not effective.

• The term daily light integral (DLI) describes this cumulative number of photosynthetic photons (400-700 nm) per square meter in one day

• The –2 –1, or simply mol/day

Quantity of light: Daily light integral December

February

January

March

Large ModerateBenefit of supplemental lighting

Small



• One of the most economical uses of supplemental lighting is on plugs and liners.

• This is especially important in northern latitudes because a majority of plugs and liners are produced late in the winter and early spring, when the daily light integral is low.

• A typical supplemental lighting recommendation for ornamentals is to deliver 60 to 90 mol m–2 s–1 for up to 18 hours per day

During low-light periods, providehigh-intensity lighting

6 10 16

22 days from seed sow at 73 °FGrown under an average DLI of: (mol m-2 d-1)

Salvia ‘Vista Red’

High-pressure sodium (HPS)

Traditional (single-ended) HPS lamp (400 to 1,000 W)

Double-ended HPS lamp (600 to 1,000 W)

Sources: Nelson and Bugbee, 2017; www.designlights.org/horticultural-lighting

Fixture modelLight output

s–1)Efficacy

J–1)High-pressure sodium (HPS)

Sunlight Supply Sun Star HPS (400 W, magnetic) 416 0.94P.L. Light SON-T PIA HPS (600 W, electronic) 926 1.34Gavita Pro 1000e HPS (1000 W, dbl-end electronic) 1,837 1.72

LEDsFluence VYPR 3P Toplight HR9 (96%R) 2,311 3.69Philips GP Interlight 300 DRB (94% R) 323 3.63Philips GP Toplight Compact 1750 DRW_MB (84%R) 1,700 3.30Fohse A3i 1500 (58% R) 4,971 3.18P.L. Light Systems HortiLED Top 2.0 RWMB (85% R) 1,085 3.18GE Current Arize Lynk GEHL48HPPB3 (79% R) 98 3.04

Examples of supplemental lighting fixture efficacy

Temperature Influences

• Rate of development (time to flower)

• Plant quality

– Flower size and number

– Leaf characteristics

• Plant height (DIF)

Temperature (°F)

Rela

tive

dev

elop

men

t rat

e

0

maximum

32 41 50 59 68 77 86 95

Snapdragon

Pentas

Basetemperature

Optimumtemperature



Angelonia ‘Serena Purple’Constant temperature (°F):

Average DLI: -2 -1

41 45 50 59 68 77

Dead 60 34 29Dead Dead

86

31Days from transplant of 288-cell plug to flowering

Cosmos ‘Cosmic Orange’Constant temperature (°F):

Average DLI: -2 -1

Dead 42 30 29Dead 69 56

41 45 50 59 68 77 86

Days from transplant of 288-cell plug to flowering

• Temperature controls the rate of plant development• DLI influences:

– Shoot and root biomass– Plant temperature– The leaf (node) number at which plants are

induced to flower• Precise scheduling requires temperature,

photoperiod, and DLI inputs

Temperature and DLI interact to controlgrowth and flowering

Virtual Grower 3.1

A software program developed by the USDA-ARS in Toledo, Ohio that can be used to:

• Schedule bedding plants• Predict energy consumption• Assess savings opportunities• Guide potential investments and grant opportunities

Download it free atwww.virtualgrower.net

Geranium ‘Florever Violet’8 weeks from transplant at (°F):

63 68 73

93 76 64

Predicted days to flower from transplant of 288-cell plug

70 57 49

5

12

79

54

41

Petunia ‘Easy Wave Neon Rose’16-hour photoperiod at constant (°F):

54

14mol -2 -1

7mol -2 -1

73 58 49 38 35

55 49 40 32 28Average days to flower from transplant of 288-cell plug

Photos taken 37 days after transplant

59 64 70 75



Transplant Date to Achieve Flowering of Petunia ‘Wave Purple’ for April 1

Apr 1Avg Temp

58 °F

63 °F

73 °F

68 °F

79 °F

Finish

Finish

Finish

Finish

Finish

Mar 20Mar 8Feb 24Feb 12Jan 31Jan 19

64 days

47 days

30 days

37 days

26 days

with a 16-hour photoperiod

*Time to flower is from transplant of 288-cell plugs that were grown at 68 °F and under a 16-hour long day.

Petunia ‘Wave Purple’

Average Daily Temperature (°F):58 63 68 73

Days to flower from transplant

Heating costs to produce crop in Madison, WI for April 1($ per ft2 per crop)

64 47 37 30

0.33 0.25 0.20 0.19

79

26

0.18


Petunia ‘Wave Purple’

Average Daily Temperature (°F):58 63 68 73

Days to flower from transplant

Heating costs to produce crop in Madison, WI for May 15($ per ft2 per crop)

64 47 37 30

79

26


0.13 0.09 0.08 0.08 0.09

Average temperature (°F):7357 6763 78

Effect of Temperature on Flowers

MSU Floriculture Websitewww.canr.msu.edu/floriculture

Take-home messages

• If using poly, use infrared film for the inside layer• Reduce air leaks / add insulation• Install / maintain horizontal air flow fans• Install/maintain retractable energy/shade curtains at night• Start with larger transplants grown under high light• Use low-intensity LED lighting on long-day plants until April 1• Deliver high-intensity lighting when growing young plants• Growing cool may consume more energy on a per-crop basis



MSU Acknowledgments

• MSU Floriculture Team: Matthew Blanchard, Tasneem Vaid, Lee Ann Moccaldi, and Mike Olrich

• Private horticulture companies and granting agencies that have financially supported the MSU Floriculture research program

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Energy-Efficient Bedding Plant Production