Produce High-Quality Rooted Cuttings

Fig. 1. Propagation bench with no shade cloth or shade cloth providing 31 percent, 68 percent or 86 percent shade. Supplemental light from high-pressure sodium lamps are used to create four different daily light integrals during root development.

Whether you are a propagation specialist or are rooting cuttings for your own in-house production, the goals of propagators are the same — to efficiently produce high-quality rooted cuttings. In order to meet the spring and early summer market dates for flowering bedding plants, cuttings are typically rooted in mid- to late-winter and early spring when the outdoor daily light integrals (DLIs) are at seasonally low levels. The DLI inside a greenhouse is often further reduced as a result of glazing material and interior structures, as well as hanging baskets suspended above benches to maximize production space.

Research has recently shed some light on the impact of light levels during propagation of New Guinea impatiens and petunias. However, the number of species and cultivars grown from cuttings is quite large and diverse. Therefore, we wanted to better understand the impact of DLI during propagation on growth and quality of several vegetatively propagated annual bedding plant species.

How the Study Was Conducted

Cuttings of Angelonia ‘AngelFace White,’ Argyranthemum ‘Madeira Cherry Red,’ Sutera ‘Abunda Giant White (bacopa),’ Diascia ‘Wink Coral,’ Lantana ‘Lucky Gold,’ Nemesia ‘Aromatica Royal,’ Osteospermum ‘Voltage Yellow,’ Scaevola ‘Blue Print’ and Verbena ‘Aztec Violet’ were stuck in 105-cell trays filled with a propagation substrate that was 50-percent soilless substrate and 50-percent coarse perlite. Cuttings were maintained in a propagation greenhouse with an air and substrate temperature set point of 73°F. During the first seven days of callusing, the average DLI was maintained at about 5 mol•m¯²•d¯¹.

After seven days, cuttings were placed in a greenhouse with high-pressure sodium lamps operating for 16 hours per day with either no shade cloth or shade cloth providing 31 percent, 68 percent or 86 percent shade (Fig. 1). We repeated the experiment two additional times to achieve a span of DLIs representing a range of greenhouse DLIs, from 1.2 (very low) to 12.3 mol•m¯²•d¯¹ (moderately high). Two weeks after being placed under the shade/lighting treatments, rooted cuttings were harvested. We measured stem length and caliper and washed the substrate off the roots so we could separate roots and shoots to record dry weights.

Supplemental Lighting Increased Both Shoot And Root Growth

Shoot dry weight (a measure of plant size) increased for all species as DLI increased during propagation, though species also varied in the magnitude of their response (Figs. 2 and 3). As DLI increased from 1.2 to 12.3 mol•m¯²•d¯¹, shoot dry weight of all species increased, from 50 percent (lantana) to 384 percent (diascia).

More importantly for cutting propagators, increasing DLI increased the root dry weight for all nine species. For example, increasing the DLI by 11 mol•m¯²•d¯¹ resulted in a 156 percent increase in root dry weight of verbena, while root dry weight of diascia increased by 1,137 percent. Additionally, the root:shoot dry weight ratio increased for all species as DLI during propagation increased. While the root:shoot ratio of verbena increased by 18 percent as DLI during propagation increased, the root:shoot ratio of osteospermum and scaevola increased by 329 percent and 419 percent, respectively. This means that although both shoot and root growth increased with DLI, cuttings allocated more growth into roots as opposed to shoots.

Increased DLI Has Variable Effect On Stem Length

While shoot and root growth increased with DLI for all species, there was no consistent trend in stem length in response to DLI during propagation. For example, as DLI during propagation increased from 1.2 to 12.3 mol•m¯²•d¯¹, the stem length of lantana and nemesia both increased by 20 percent while stem length of diascia increased by 76 percent.

Alternatively, stem length of argyranthemum, osteospermum and scaevola was unaffected by DLI during propagation. Similarly, stem caliper of bacopa, lantana and scaevola were unaffected by DLI, while stem caliper of angelonia, argyranthemum, diascia, nemesia, osteospermum and verbena increased with DLI during propagation by 11 percent (verbena) to 119 percent (diascia).

Measuring The Impact On Plant Quality

We often talk about plant quality, and several attributes contribute to our perception of this. It is generally desirable to have rooted cuttings and plugs with good root and shoot growth, a higher root:shoot ratio. They should be sturdy and not too leggy. Though we collected all of this data for cuttings, we wanted to integrate it to assess overall quality.

To do this, we used something we called the “quality index” (Fig. 4), a
value derived from an equation combining the total mass, root:shoot ratio and the ratio of stem caliper to stem length. The quality index increased differently for all species as DLI during propagation increased from 1.2 to 12.3 mol•m¯²•d¯¹, from 53 percent (lantana) to 960 percent (diascia).

Supplemental Lighting May Save Money  

In addition to producing high-quality rooted cuttings, lighting during propagation may actually save you money by reducing overall production time for rooted cuttings. How can adding supplemental light reduce energy costs? Let’s look at a few examples using Virtual Grower, a tool developed by the USDA-ARS to estimate energy consumption during greenhouse production. We will start by simulating propagation of angelonia in a 1-acre glass-glazed greenhouse in Indianapolis, Ind., in March.

Assuming an average greenhouse DLI of ~5 mol•m¯²•d¯¹, production will take about five weeks. Our day and night temperature set points will be 73°F and 70°F, respectively, for the first four weeks (callusing and rooting), followed by one week of 73°F days and 65°F nights (toning). It would cost approximately $1.02/ft² for the five-week period to finish angelonia cuttings if you are heating with propane. Now, if we provide 75 µmol•m¯²•d¯¹ (577 foot-candles) for 18 hours using 400-W HPS lamps this will provide ~5 mol•m¯²•d¯¹, bringing our total DLI up to approximately 10 mol•m¯²•d¯¹ during root development and toning.

The energy costs for operating the HPS lamps would be $0.03/ft²for the three-week lighting period. However, our heating costs are reduced, because under the higher DLI the cuttings finish one week earlier. Therefore, when the total energy cost for producing rooted angelonia cuttings with supplemental light ($0.86/ft²) is compared to no supplemental light ($1.02/ft²), we can realize a 15 percent savings.

Let’s look at another example using a species that has a stronger response to DLI during propagation  — argyranthemum. Using the same production facility and temperatures already described, we would have the same energy cost for heating during the five weeks of production — $1.02/ft². When we add the same supplemental light after a week of callusing, our cuttings would be finished in a total of three weeks. Our total energy costs for two weeks of supplemental lighting and three weeks of heating would be $0.77/ft², resulting in a 25 percent reduction in energy costs compared to argyranthemum cuttings rooted without supplemental light.

When interpreting these costs, it is important to know that energy costs will vary with greenhouse structures and glazing material, location and time of year. However, we think these examples are useful in seeing how lighting during propagation may affect your production costs.

Consider Whether Supplemental Lighting Will Work For You    
If you are currently rooting cuttings and looking for ways to improve both the quality of your liners and your efficiency in production, we encourage you to evaluate using supplemental light during propagation. A good starting point would be to begin monitoring the DLI in your propagation area to see how much light you are receiving during propagation.     GG

Leave a Reply

One comment on “Produce High-Quality Rooted Cuttings

  1. Buenas tardes, quiero agradecerles por poner a nuestra disposición este aclarador estudio y quisiera saber si han probado ustedes con esquejes de crisantemo y si es necesario dar luz suplementaria en las noches a el esqueje antes de que forme sus primeras raices. Muchas gracias Saul Correa

More From Technology...
Drone for Bee Pollination

February 21, 2017

Learn How Drones Could Eventually Replace Bees in Pollinating Crops

Researchers in Japan are using the principle of cross-pollination in bees to make a drone that could potentially transport pollen between flowers.

Read More

February 15, 2017

Registration Open for NGMA Spring Meeting

The annual gathering of the National Greenhouse Manufacturers Association will feature a look at green industry trends, emerging market opportunities, and more.

Read More
Visser PC 16 Transplanter feature

February 13, 2017

How to Find a Greenhouse Transplanter for Every Grower’s Budget

Equipment manufacturers have recognized a void in the market for machinery that appeals to growers of all sizes and budgets. Here are some affordable options to consider investing in to improve your operation’s efficiency.

Read More
Latest Stories
Drone for Bee Pollination

February 21, 2017

Learn How Drones Could Eventually Replace Bees in Polli…

Researchers in Japan are using the principle of cross-pollination in bees to make a drone that could potentially transport pollen between flowers.

Read More

February 15, 2017

Registration Open for NGMA Spring Meeting

The annual gathering of the National Greenhouse Manufacturers Association will feature a look at green industry trends, emerging market opportunities, and more.

Read More
Visser PC 16 Transplanter feature

February 13, 2017

How to Find a Greenhouse Transplanter for Every Grower&…

Equipment manufacturers have recognized a void in the market for machinery that appeals to growers of all sizes and budgets. Here are some affordable options to consider investing in to improve your operation’s efficiency.

Read More
Emerald Coast Growers Seed Room

February 8, 2017

Emerald Coast Growers Adds New Seed House to Increase P…

The new facility is designed to increase the company’s control over inventory, sowing rates, germination percentages, and growing conditions.

Read More
ISO Cutting Machine

February 4, 2017

Getting to the Next Generation of Greenhouse Automation

The most successful growers in the future will be those that are willing to accept and invest in new technology.

Read More
TopCrop Monitor (Priva) feature

February 2, 2017

The Latest Updates in Greenhouse Environmental Controls

Constant monitoring of your greenhouse climate is critical, especially when you can’t be there in person. Here’s a look at what manufacturers have developed to make this process more efficient and effective.

Read More
DRAMM PulsFOG

February 1, 2017

DRAMM: 75 Years of Innovation

This manufacturer and distributor of horticultural tools and equipment has a long history of developing inventive new technology that solves problems for its customers.

Read More
LumiGrow Gerbera feature

February 1, 2017

How Lighting Companies Are Tackling Plant Quality

Working with researchers and growers, three suppliers have learned how effective lighting can lead to healthier crops.

Read More
Botany Lane Greenhouses

January 27, 2017

Why Botany Lane Grows Poinsettias On Capillary Mats

A move to watering mats cut water and fertilizer use, production time, and labor for this Colorado-based grower.

Read More
Ever Bloom Robot Sprayer feature

January 23, 2017

New Automation Systems Improve Spraying and Harvesting

In response to increasing regulations on labor, Ever-Bloom Inc. decided to invest in new automation technology that also dramatically improves efficiency.

Read More
Bouldin and Lawson Precision Needle Seeder feature

January 19, 2017

How You Can Get More Precise With Your Seeder

Bouldin & Lawson’s Precision Needle Seeder is designed to improve accuracy when sowing small, difficult seeds.

Read More
EFTE Film

January 18, 2017

Looking at Glass or Polyethylene for Your New Structure…

Ethylene Tetrafluoroethylene, also known as EFTE, is a fluorine-based material that looks like a standard polyethylene greenhouse film but offers high light transmittance.

Read More
PC-31 Transplanter (Visser)

January 17, 2017

Visser NA Rebrands as Bellpark Horticulture

The new name will equally represent not only Visser, but all of the brands Bellpark represents, including Mayer, Logitec Plus, and Drygair in North America.

Read More
visser-irrigation-booms-with-damatex-controls-at-north-creek

December 22, 2016

Webinar Series In Early 2017 Will Address Greenhouse Wa…

Beginning on Jan. 24, experts from Clean WateR3, a federally-funded research team, will present topics that are focused on helping growers reduce, remediate, and recycle irrigation water.

Read More
costa-farms-corp-solar-pv-panels-1-feature

December 21, 2016

Technology Helps Costa Farms Track And Reduce Energy Co…

Costa has realized significant energy cost savings by auditing how its farms are using energy, and implementing new technology to increase efficiency.

Read More
mcconkey-plastic-shelves-feature

December 1, 2016

How Color Point Is Stopping Cart Theft With Plastic She…

Plastic shelving on carts acts as a deterrent to theft, and employees enjoy the benefits of being able to handle the racks without difficulty or injuries.

Read More
oasis-water-valve-feature

November 30, 2016

How You Can Water Plants Based On Basket Weight

The Oasis from Control Dekk is designed to reduce water use by giving baskets the exact amount of water they need.

Read More
Silver Bullet Heaters (Heat Star By Enerco) Feature

November 28, 2016

The Latest In Greenhouse Heating And Cooling Products

New developments in heating, cooling, ventilation, and humidity control technology are designed to help you manage your greenhouse environment more efficiently. Check out some of the latest offerings from leading manufacturers.

Read More