Energy-Efficient Annuals: Petunias

Energy-Efficient Annuals: Petunias Images

Escalating fuel costs have made it important for greenhouse growers to improve production efficiency and schedule crops more efficiently. At Michigan State University (MSU), we have performed experiments with many seed-propagated annuals to quantify how temperature and daily light integral (DLI) influence flowering time and plant quality. In the sixth article of this series, we present crop timing data on petunias and then use this information to estimate greenhouse heating costs at different locations, growing temperatures and finish dates.

Petunias are among the top 10 bedding plants produced in the United States. In 2008, the 15 largest floriculture-producing states collectively sold 34.5 million flats, pots and hanging baskets at a total wholesale value of $120 million. Among the different species and hybrids of petunias available, our studies have included grandiflora petunia ‘Dreams Neon Rose,’ milliflora petunia ‘Fantasy Blue,’ and spreading petunias ‘Easy Wave Coral Reef’ and ‘Wave Purple.’

Materials and Methods

Seeds of each petunia variety were sown in 288-cell plug trays by C. Raker & Sons, then grown in controlled environmental growth chambers at MSU at 68°F (20°C). Inside the chambers, the photoperiod was 16 hours (an inductive long day) and the DLI was 9 to 11 mol∙m¯²âˆ™d¯¹.

When plugs were ready for transplant (27 to 35 days after seed sow), they were thinned to one seedling per plug and transplanted into 4-inch pots and grown in greenhouses with constant temperature set points of 57, 63, 68, 73 and 79°F (14, 17, 20, 23 and 26°C). At each temperature, plants were grown under a 16-hour photoperiod with two different DLIs provided by a combination of shade curtains and different supplemental lighting intensities from high-pressure sodium lamps.

Some petunia varieties such as ‘Dreams Neon Rose’ do not require long days for flowering, but flower faster if grown under long days. Other petunia varieties such as ‘Wave Purple’ are obligate long-day plants and must be grown under long days for flowering. Therefore, when producing petunias under naturally short day lengths (less than 13 to 14 hours), photoperiodic lighting will accelerate flowering and shorten cropping time.

Our experiments were performed twice to obtain average DLIs that ranged from 4 to 20 mol∙m¯²âˆ™d¯¹. To give perspective, a DLI of 4 mol∙m¯²âˆ™d¯¹ is representative of light conditions received by a northern greenhouse on a cloudy day in the winter; a DLI of 20 mol∙m¯²âˆ™d¯¹ is typical for a mid- to late spring day. The flowering date was recorded for each plant when the first flower opened, and at that time, plant height, number of leaves and number of flowers and flower buds were recorded.

Crop timing data were used to develop mathematical models to predict flowering time and plant quality under different temperature and DLI conditions. The scheduling models were validated by growing petunias at three different constant temperatures to compare predicted flowering times with actual times. The Virtual Grower software (available free at VirtualGrower.net) was used to estimate the cost to heat a 21,504-square-foot greenhouse (about half an acre) to produce each crop for different finish dates and at different locations in the United States.

Results

In all petunia varieties, time to flower decreased as average daily temperature increased. For example, in ‘Dreams Neon Rose’ grown under a DLI of 10 mol∙m¯²âˆ™d¯¹, time to flower from a 288-cell plug decreased from 40 days at 58°F to 20 days at 73°F (Figure 1). At the same DLI, ‘Wave Purple’ flowered almost five weeks later at 58°F versus 73°F (Figure 2). Petunia ‘Fantasy Blue’ grown under 10 mol∙m¯²âˆ™d¯¹ and at 58, 63, 68, 73 or 79°F flowered in 27, 22, 19, 17 and 15 days, respectively. Petunia ‘Easy Wave Coral Reef’ grown under 10 mol∙m¯²âˆ™d¯¹ and at 58, 63, 68 or 73°F flowered in 46, 35, 28, 23 and 19 days, respectively.

An increase in DLI also accelerated flowering of petunia. For example, for plants grown at 63°F, time to flower decreased by four days in ‘Dreams Neon Rose,’ 13 days in ‘Fantasy Blue,’ and 11 days in ‘Easy Wave Coral Reef’ and ‘Wave Purple’ when DLI increased from 4 to 10 mol∙m¯²âˆ™d¯¹. The estimated saturation DLI for the shortest time to flower was 10.5 mol∙m¯²âˆ™d¯¹ for ‘Dreams Neon Rose,’ 16 mol∙m¯²âˆ™d¯¹ for ‘Easy Wave Coral Reef,’ and 14 mol∙m¯²âˆ™d¯¹ for ‘Wave Purple.’ In other words, increasing the DLI above these values did not shorten crop time. Flowering time continued to decrease as DLI increased for ‘Fantasy Blue’ and thus, the saturation DLI is greater than 20 mol∙m¯²âˆ™d¯¹. Using this research data, we identified dates that 288-cell plugs grown under long days need to be transplanted for two market dates when grown at different temperatures under long days (Table 1).

The number of flower buds at first flowering increased as average daily temperature decreased and as DLI increased. For example, in petunia ‘Wave Purple’, the number of flower buds increased by 75 percent as DLI increased from 5 to 15 mol∙m¯²âˆ™d¯¹. In all petunias, plants had the fewest flowers when grown at the warmest temperature (79°F) and under the lowest DLI (4 mol∙m¯²âˆ™d¯¹). Plant height at flower increased as DLI decreased.

As most growers already know, crop timing varies significantly among petunia varieties. In the four petunias we studied, crop timing at 68°F varied from 19 to 37 days even when light conditions were nearly identical during the plug and finish stages. Similarly, increasing the DLI had different promotive effects on the varieties studied. However, all crops flowered faster, and plants were of higher quality, when the DLI was increased to at least 10 mol∙m¯²âˆ™d¯¹.

Heating Costs

This crop timing information can be used with Virtual Grower to identify the most energy-efficient production temperature for different dates and locations. According to our predictions, heating costs for a crop of petunia ‘Dreams Neon Rose’ grown for April 1 in San Francisco, Calif., Tallahasee, Fla., Charlotte, N.C., or Fort Worth, Texas, would be 13 to 38 percent lower at a constant 58°F versus 73°F (Table 2). To produce the same crop in northern locations such as Grand Rapids, Mich., New York, N.Y., or Cleveland, Ohio, heating costs per square foot would be 22 to 29 percent higher at 58°F versus 73°F. In other words, it is more energy-efficient for growers in the north to start spring production later and grow at a warmer temperature.

Petunia ‘Wave Purple’ grown under 10 mol∙m¯²âˆ™d¯¹ for April 1 in Grand Rapids, Mich., New York, N.Y., or Cleveland, Ohio would cost 9 to 21 cents less per square foot if grown at 68 or 73°F versus 58°F. Therefore, a grower with a half-acre greenhouse would save $1,960 to $4,574 on heating costs per crop by transplanting later and growing warm. In addition, ‘Wave Purple’ grown at 68 or 73°F would flower four to five weeks earlier than at 58°F, which would make production space available for additional crops.

The cost of energy for heating is just one of the many production expenses for greenhouse crops. Other factors, such as the number of crop turns and overhead costs, should also be considered when choosing the most economical growing temperature for each floriculture crop producer.

Leave a Reply

More From Annuals...

June 30, 2015

Opportunities Abound For Women In Horticulture, Says Dosatron International’s Lela Kelly

My love for horticulture goes back to my grandparents who were farmers in upstate New York. My family’s involvement in agriculture left a lasting impression that has spanned decades, and still drives my passion for our industry today. I started my career in horticulture when I owned a greenhouse, nursery and garden center in Sayville, Long Island, N.Y. We specialized in ground cover production, later branching out to producing perennials and bedding plants.     I then went onto wholesale hard goods distribution. In the 1980s, I was the first woman salesperson on Long Island. What an eye opener that was! New York is a very special place, different from anywhere else in the country. You cannot imagine how difficult it was walking into greenhouses and nurseries as a woman, in a man’s world. Luckily, I grew up in New York City in an Italian family, who taught me great […]

Read More
Medal of Excellence Award

June 30, 2015

Get To Know The 9 Variety Finalists For Editor’s Choice And Industry’s Choice Awards

Greenhouse Grower‘s Evening Of Excellence reception is rapidly approaching. Here, you can learn more about the varieties that are finalists for the Medal Of Excellence Editor’s Choice and Industry’s Choice Breeding Awards. Thank you to the 2015 sponsors of Greenhouse Grower‘s Medal Of Excellence Awards, Landmark Plastic, Nufarm and Stockosorb. Editor’s Choice Asclepias ‘Monarch Promise’ (Hort Couture) Basil ‘Balsamic Blooms’ (EuroAmerican Propagators) Celosia ‘Dragon’s Breath’ (Sakata Seed) Dianthus Jolt Series (PanAmerican Seed) Salvia Grandstand Series (Green Fuse Botanicals) Scabiosa ‘Kudos Pink’ (Hishtil Nurseries) Industry’s Choice Basil ‘Balsamic Blooms’ (EuroAmerican Propagators) Bidens BeeDance Series (Suntory Flowers) Celosia ‘Dragon’s Breath’ (Sakata Seed) Dianthus Jolt Series (PanAmerican Seed) Lobelia ‘Starship Deep Rose’ (Kieft Seed) Vinca Valiant Series (PanAmerican Seed)     Join us Monday, July 13 in Ballroom 2 at the Columbus Convention Center to find out which varieties will receive the coveted awards. The reception begins at 5:15 p.m. and the ceremony […]

Read More
lighting feature

June 29, 2015

Customizing Crop Foliage Color With LEDs: Red Leaf Lettuce

In the first of a four-part series highlighting the multiple uses of light-emitting diodes (LEDs), researchers share how end-of-production supplemental lighting with LEDs enhances red leaf lettuce color prior to harvesting and shipping.

Read More
Latest Stories
WavePetunias-GrowIt_contest_featured

June 18, 2015

Wave Petunias Sponsors Photo Contest Through GrowIt! Ga…

The gardening season is heating up and the Wave Petunias Team wants to see the #WildestWave. The popular plant brand has joined forces with the GrowIt! Garden Socially app to host a two week contest in June that encourages Wave Fans to share and rate photos of their favorite Wave Petunias. The grand prize is a $100 gift card to the garden center of the winner’s choosing. “We are excited to work with GrowIt! and see our Wave Petunias tagged in cities from coast to coast,” says Claire Watson, brand manager for Wave. “Seeing gardeners’ creative photography, awarding a winner, and learning what each region likes about Wave Petunias will be extremely useful as we further promote our ‘Wow ’em With Wave’ ad campaign this season.” Gardeners can place an entry into the contest by downloading GrowIt!, filling out a profile, and uploading photos of Wave Petunias. Placing the tag #WildestWave in the photo’s comments section […]

Read More
Salvia 'Ember's Wish'

March 11, 2015

Annual Salvias – Not Just Red Bedding Plants Anym…

Salvias are popular — and they need not all be the same. Here are a few you know well, and perhaps a few you do not. All are easy to grow and may be found through a broker or grower.

Read More

February 18, 2015

California Spring Trials Sneak Peek: New Annuals For 20…

If you're like us and you can't wait until the 2015 California Spring Trials to see some of the new genetics that will be hitting the market in 2016, never fear. We contacted the breeders who will be displaying their new varieties in California in April, and they gave us a sneak peek. Check out our slideshow to see some of the new annuals making their debut to the trade this spring.

Read More

November 14, 2014

First Vegetatively Propagated All-America Selections (A…

All-America Selections (AAS) honors two vegetatively propagated impatiens with AAS winner status.

Read More

October 13, 2014

Growing Tips For Verbena

Rich Schoellhorn, product manager at Proven Winners, shares some tips for growing verbenas successfully.

Read More

October 13, 2014

Greenhouse Grower 2014 New Varieties Guide: Petunias [S…

Greenhouse Grower asked more than 40 breeders to send photos of new introductions they think are worth your attention. The result is the 2014 New Varieties Guide. See what petunias made the cut.

Read More

June 12, 2014

New Begonia Variety And Coleus Series, Plus Two Lobelia…

Terra Nova Nurseries introduces seven new varieties and one new series.

Read More

May 27, 2014

Two New Salvias Added To Southern Living Plant Collecti…

Two new salvia varieties are now available exclusively to growers from the Southern Living Plant Collection and Sunset Western Garden Collection.

Read More

May 9, 2014

New Petunias Making Their Debut In 2015

Take a look at the new petunia varieties that will be making their appearance in 2015.

Read More

April 23, 2014

Foliage Begonias May Be A Big 2015 Trend [Spring Trials…

A number of breeders debuted their rex begonia and begonia hybrid lines at 2014 Spring Trials.

Read More
Petunia 'Success Violet' from Benary

April 11, 2014

What’s New With Petunias For 2014? [Slideshow]

Breeders are rolling out great new petunia introductions for 2014. Take a look at the variety of petunias they have to offer.

Read More
Verbena 'Superbena Royale Whitecap' from Proven Winners

November 11, 2013

Three New Verbena Superbena Introductions From Proven W…

Three new varieties have joined the verbena Superbena line-up this year: 'Superbena Royale Plum Wine,' 'Superbena Royale Whitecap' and 'Superbena Violet Ice.'

Read More
Calibrachoa 'Mini Famous Double Blue' from Selecta

October 17, 2013

6 New Calibrachoa For 2013

Check out these lovely new introductions in calibrachoa.

Read More

October 10, 2013

Begonia ‘Silhouette Lemon Rose’ Doubles The Bloo…

Begonia ‘Silhouette Lemon Rose’ is a striking begonia hybrid with phenomenal basal and lateral branching. Plant sterility gives maximum continual flowering throughout the season with double the bloom number of a traditional non-stop begonia. Dark mahogany foliage with contrasting emerald green veining provides a dramatic contrast to the soft lemon yellow 1.5- to 2-inch diameter blooms that blush apple blossom pink in high light. This easy-care beauty is ideal for mixed pots and containers, hanging baskets or the summer border. For more information, visit PlantHaven.com

Read More
Petunia 'Flash Mob Bluerific' Burpee Home Gardens

October 7, 2013

18 New Petunias To Add For 2014

Tried and true, petunias are a garden staple. Here are some new introductions breeders are rolling out for your consideration in 2014.  

Read More
Verbena 'Hurricane Hot Pink' from Westflowers

October 7, 2013

New Verbena For 2014

Check out these eight new verbena varieties and consider them for your 2014 greenhouse production.  

Read More
Dahlia Dalaya Shari from Selecta

September 25, 2013

4 New Dahlias For Your 2014 Season

Looking for new dahlia varieties to incorporate in your crop mix? Here are 4 beauties your customers will love.  

Read More
'Wall Street' Coleus from Dummen/Red Fox

September 25, 2013

4 Colorful New Coleus For 2014

Gorgeous foliage makes these new introductions must-haves for next year.  

Read More