Mechanize your growth control

Growers have limited options when it comes to controlling plant growth to induce lateral branching, to insure uniform height and to control crop timing. Traditional strategies have involved manual pinching or trimming and/or applying plant growth regulators. When choosing a growth control strategy, growers need to consider the following issues:

Cost. Manual pinching is labor intensive. Growth regulators have labor and product costs associated with their application.

Speed. Manual pinching is a slow, time-consuming process. Pinching a large crop can often take days and may require several employees. Although growth regulator applications are faster, there is still the time involved with preparation and clean up as well as the application time itself.

Predictability of results. Manual pinching and/or using growth regulators can sometimes have unpredictable and even unintended results. Consistency and uniformity are important criteria for producing a quality crop.
Most growers know how many times, and when, they would like to pinch a particular crop. However, doing these pinches can be constrained by the issues discussed previously. At times, growers may be forced to use growth regulators as a substitute for pinching, do the pinch later than desired or not do a pinch at all.

“Pinch timing and frequency is very important, and PGRs should not be used as a substitute for a pinch,” said Steve Zylstra, owner of Zylstra Greenhouses in Kalamazoo, Mich.

Manual pinching is labor intensive and a slow, time-consuming process. Pinching a large crop can often take days and may require several employees. Manual pinching can sometimes have unpredictable and even unintended results. An alternative solution
Some growers are turning to a more automated approach to manual pinching by investing in motorized, mechanical trimmers. Growers who have made the switch have realized a substantial cost savings.

“We are reducing our labor cost 80 percent by using our trimmer to pinch poinsettias instead of manual pinching,” said Marc Verdel, head grower at Battlefield Farms in Rapidan Va. “These savings also apply to the mums we pinch, as well as plants such as [Dummen] Confetti varieties, verbena and vinca vine.”

Another benefit growers have realized from the trimmers is speed, which has led to greater flexibility.

“Often our optimal window for pinching is only one or two days, and the call has to be made quickly, based on the condition of the crop,” Zylstra said. “If it takes two or three days to do a manual pinch, not to mention the time needed to pull together the necessary labor, we can miss our window. With the trimmer, most of our pinches are done in less than half a day, with minimal labor, exactly at the right time for the best results.”

An over-the-ground trimmer being used on a crop of poinsettias.Because of the speed and labor savings, growers can fine tune production management to focus on the timing and fullness of a crop. A trimmer can allow a grower to respond quickly to different crop situations in a timely manner with predictable results.

“When someone walks into our greenhouse and looks at a crop, we want them to see a putting green in terms of uniformity,” said Brian Decker, owner of Decker’s Nursery in Groveport, Ohio. Decker was most impressed with the trimmer’s consistency and uniformity when it was first demonstrated at his operation.

“It’s hard to imagine consistent results when you picture eight workers, each with hand cutters, pinching a crop with eight different ideas about how a plant should be pinched,” said Zylstra. “Our trimmer provides us with a high level of consistency compared to manual pinching.”

Trimmer models available
The two main types of trimmers commercially available are over-the-ground trimmers and conveyor-fed trimmers. Each is designed and engineered for particular types of trimming.

An over-the-ground trimmer rolls over a row of plants with the cutting head suspended between the wheels. As the unit is pulled down the row, the plants are sheared by precision blades that have been set at a specific height, typically with a 60-inch maximum cutting width and a maximum cutting depth of 5 inches per pass.

A conveyor-fed trimmer uses a variable speed conveyor to feed flats or pots into the cutting blades. Typical maximum cutting widths are between 16-20 inches with a maximum cutting depth of 5 inches per pass. These trimmers are designed for younger and more delicate plants. The conveyor-fed trimmer can be equipped with precision “pinching” blades which can be speed controlled. A vacuum system stands the plants up straight for even and uniform cutting. There are also blowers that direct air upward. The blowers work in conjunction with a suction shroud to ensure trailing plants like vinca vine get pulled up for trimming. The conveyor-fed trimmer is equipped with wheels allowing it to be easily moved to different locations.

Both trimmer types integrate a collection system for clippings that do not damage the cuttings, which allows them to be reused. Both units are equipped with safety and ease-of-use features that ensure safe operation and a short learning curve.

Practical considerations
Before investing in a mechanical trimmer, consider the following factors.

• Training and learning curve. Growers who have purchased the trimmers said there was a short learning curve for their employees to operate the machines. The power and speed of the trimmers dictate competent set up and control to avoid damaging crops and getting optimal results.
• Maintenance and supplies. Just like any other machine in the greenhouse, a trimmer has to be maintained. Periodic lubrication, cleaning, and blade sharpening help keep the machines in good working order. Some growers have purchased additional clipping bags that enable the trimmer to continue operating while the other clipping bags are removed for emptying.
• Sterilization. Just like with hand pinching, sanitation precautions must be taken for disease control. Blades can be sterilized with a hydrogen peroxide spray solution. Growers have purchased multiple sets of blades in order to operate the trimmers while other blades are being sterilized after switching to a different crop.
• Safety. The machines are designed for safety with multiple guards and lockouts to keep users away from the cutting blades. These are powerful cutting machines and safety procedures should be established and strictly enforced.
• Volume and type of trimming. Depending on the operation and crops, a grower will need to determine if there is a sufficient volume of plants to justify purchasing a mechanical trimmer. Also, the grower will have to decide if an over-the-ground or a conveyor-fed trimmer or both are most appropriate. A trimmer supplier can help answer these questions.
• Cost. An over-the-ground model can cost as little as $9,700. It can cut a row 60 inches wide, almost as fast as it can be pulled. For pinching poinsettias, a $1,200 air blow down kit is available. The conveyor-fed type trimmer ranges from $15,500-$19,000, depending on the options.
   

“Our trimmer takes the hassle factor out of pinching. We get our pinches done on time; with less labor, allowing us to do more pinches than we could before.” Decker said. “We calculated a payback period of one season for our trimmer, accounting for its use in only one greenhouse and we have 24 greenhouses.” 

George Russell is vice president sales and marketing, AgriNomix, (800) 354-3750; www.agrinomix.com/trim.