Here’s how to properly control branching during the busy spring season.

Spring bedding plant season is a race to produce high-quality, flowering finished containers quickly to allow for successive crop turns. While there are a number of factors contributing to what makes a plant “high-quality” and when it is finished, developed and developing branches filling in the container help bulk-up plants to fill in containers and result in an appealing plant appearance.

Starting in propagation and throughout finishing, there are several approaches to improving branching for annual bedding plants.

In plants, apical dominance and branch development are ultimately controlled by the ratio of auxin to cytokinin, as well as the ratio of auxin to ethylene.

When the ratio of auxin is high relative to cytokinin or ethylene, dominance is maintained and branch development is suppressed. Alternatively, when auxin concentration relative to cytokinin or ethylene is low, apical dominance is released and branches develop. Actively growing shoot or stem tips can maintain apical dominance and suppress the development of branches, by forming auxin and transporting it downwards, which keeps the concentration of auxin higher near those axillary buds which may otherwise develop into branches. As stems grow taller or longer, the concentration of auxin at the base of the stem is lower, and branches start to develop. As we review the different ways to promote branching, each strategy comes back to altering the ratios auxin:cytokinin or auxin:ethylene in one way or another.

The most common method to increase branching is to pinch crops. When pinched, the site of auxin production is removed and the ratios of auxin:cytokinin and auxin:ethylene decrease; apical dominance is lost and axillary buds can develop into branches. While we call it pinching, in practice, annual bedding plants are not simply pinched in some cases — in many cases, they are sheared using some sort of hand shears or power tool such as a hedge trimmer.

The high density of plants — whether ~100-cell liner trays from propagation, shuttle trays with ten 4-inch containers or hanging basket with a half-dozen rooted liners — makes pinching individual stems impractical and shearing much more efficient. It’s not just the plant density that makes shearing an effective branching strategy, it is also the growth habit of many annual bedding plants.

Upright plants with a strong central leader like dahlias may be “pinched” in the traditional sense or have a single stem tip removed to promote branching. However, many annual bedding plants have a prostrate or spreading growth habit with multiple stems, and shearing is the most efficient means of removing all the shoot tips. No matter the stage of pruning or shearing, be sure to frequently sanitize all tools.

Although shearing is an effective means of promoting branching, the process itself can be a time- and labor-intensive one. An effective alternative to shearing is the use of plant growth regulators (PGRs). Remember, branching is controlled by the ratios of auxin:cytokinin and auxin:ethylene. In shearing, we reduce the ratio of auxin to cytokinin and ethylene by reducing auxin production in the plant.

Alternatively, we can lower the ratio of auxin to cytokinin and ethylene not by reducing the concentration of auxin, but by increasing the concentration of cytokinin or ethylene through PGR applications.

Ethephon (Florel, Collate) is an ethylene-generating PGR. While it can be used to inhibit stem elongation, flower abortion and fruit ripening, it also promotes branch development without pinching. Since ethephon is a “Swiss Army knife” PGR, it is important to always be mindful about the different effects on plants when used to improve annuals. Starting in cutting propagation, ethephon can be used to start to promote branching. Since ethephon also induces flower abortion, this can also benefit those vegetatively propagated crops developing flowers prematurely in propagation. Unfortunately, ethylene can suppress root development — the central goal of propagation.

Do not apply ethephon too early in propagation and allow roots to form and start to grow before applications; stage 3 during the root development period is a good time to start. Secondly, watch the volume of solution applied. The recommended application volume for PGR sprays is 2 quarts of solution per 100 square feet, but some growers apply PGRs “to runoff.” Do not apply ethephon solutions to runoff in propagation, and consider applying a bit less than 2 quarts per 100 square feet.

Once plants are transplanted into containers for finishing, ethephon can be applied to promote branching. While the height-suppressing activity of ethephon will almost certainly be welcome, you still need to consider the flower aborting effects. The standard recommendation has been to stop applying ethephon six weeks before flowering is desired.

However, for spring annuals in smaller containers (i.e. 4-inch pots), six weeks may exceed the total time for finishing. In my experience with many of the new vegetatively propagated annual cultivars, the cutoff time for applications does not need to be six weeks; three to four weeks is usually sufficient, which makes applications seven to 10 days after planting possible, and the full 2 quarts per 100 square feet can be used at this time.

The floriferous nature of new cultivars, especially for the multi-stemmed prostrate or spreading cultivars, allows for this shorter time from ethephon application to flowering. Please note, this shorter (three- to four-week) timeframe is based on personal experiences and observations, not careful experimentation, so proceed with caution. Start by spraying solutions with concentrations between 250 and 500 ppm to determine what works best for you.

Another PGR which can be used to promote branching without pinching or shearing spring annuals is benzyladednine (Configure). Benzyladenine (BA) is a type of cytokinin. When applied to plants, it reduces the ratio of auxin:cytokinin by increasing cytokinin concentrations relative to auxin. Be sure not to confuse Configure, a BA product, with Fascination or Fresco, a product with both BA and gibberellic acid (GA).

Unlike ethephon, BA does not have the same variety of effects on plants — it is primarily going to promote branching. While it can have slight growth-suppressing effects or short flowering delays on annuals, they are not pronounced and are usually the effect of source-sink relationships, whereby the enhanced branch growth and development competes with the main stem and flowers. Like ethephon, you can start to apply BA during propagation, but it can have the same root-inhibiting effects, so the same precautions about avoiding runoff and lower spray volumes apply for BA. Similarly, once plants are transplanted into containers for finishing, 2 quarts per 100 square feet should be used as a target spray volume and, while concentrations as low as 50 ppm can be effective on some species, up to 500 ppm BA can be applied to annuals.

Containerized annual bedding plants look better and can fill in containers more quickly when branching is improved. While shearing or pinching gets the job done, ethephon or BA can substitute for pinching to improve branching and save labor. Keep the best-management practices for these different PGRs in mind, and you can find success in the spring with these tools.

Christopher is an associate professor of horticulture in the Department of Horticulture at Iowa State University. ccurrey@iastate.edu

Check out some of the major headlines from around the industry.

Green Circle Growers, one of the largest greenhouses in North America, has announced a hiring campaign to add up to 100 workers to its growing team of employees. These entry-level roles are in anticipation of a heightened need at the holidays and beyond, and include such positions as general labor, growers, crew leaders, shipping/receiving, forklift operators, material handlers and other light industrial roles.

The company has also raised its minimum hourly rate to $17/hour for entry-level workers and is offering a $400 signing bonus and significant benefits, including medical, dental, vision, holidays and competitive 401(k) matching.

Pantone has announced PANTONE 17-3938 Very Peri as its 2022 selection for Color of the Year. Here’s what inspired this year’s choice, per the Pantone Color Institute:

Displaying a carefree confidence and a daring curiosity that animates our creative spirit, inquisitive and intriguing PANTONE 17-3938 Very Peri helps us to embrace this altered landscape of possibilities, opening us up to a new vision as we rewrite our lives. Rekindling gratitude for some of the qualities that blue represents complemented by a new perspective that resonates today, PANTONE 17-3938 Very Peri places the future ahead in a new light.

Dümmen Orange announced that they will be displaying at a new location for California Spring Trials (CAST) 2022, welcoming guests to join them at Filipponi Ranch, located at 1850 Calle Joaquin in San Luis Obispo, California.

Tour hours, available by appointment, will be as follows:

I’m not entirely sure who “they” is, but I’ve been told for most of my life that “they say laughter is the best medicine.”

Well, after two years of seemingly never-ending coronavirus developments, supply chain annoyingness and all the general uncomfortableness that's come along with the pandemic, it’s clear we could all use a good laugh as we mosey on into 2022 with a (hopefully) clean slate.

And, quite frankly, as a member of the media, I am all about taking it easy these last couple weeks of the year.

Therefore, I present this list of completely unoriginal (thank you for compiling these, Team Scary Mommy) but funny (to some) New Year’s resolutions for you to consider forgetting about by mid-January:

Here’s to a profitable and yield-filled 2022 to you and your businesses! Let’s keep all this momentum rolling in the right direction …

Supporting greenhouse and nursery growers as the newest member of the Bayer Green Solutions Team.

Jane Stanley (JS): I’ve always loved plants and got involved with horticulture in a formal way in college. After earning a master’s degree in horticulture, I went into production at a wholesale nursery. I’ve held a variety of technical roles over the last 10 years — from IPM and propagation manager, to grower, to production manager. I’ve spent the last several years in a leadership role managing all aspects of production for a container nursery.

JS: One of the things I love about horticulture is the opportunity to work at the intersection of research and applied science. For me, there’s nothing more rewarding than taking a new technique or technology, applying it in the field, and seeing the results first-hand.

JS: As part of the GST, I’m looking forward to being a bridge between the innovative teams who are developing new technology and the growers who are implementing those solutions in the field and greenhouse. As a grower, I know how difficult it can be to bring in new products and try to figure out where they fit in an existing program, as well as the economic risk of something not working or causing an unintended problem. I’m excited to partner with growers to remove some of those barriers and help them be successful.

JS: I think the biggest challenges are the same for the ornamental industry as for many others right now: supply chain issues and labor shortages. The pandemic has changed how many companies do business. Inventory management and employee retention at all levels are huge concerns. At the same time, the past two years have seen a renewed interest in gardening that none of us would have predicted. Our biggest opportunity right now is maintaining the attention and enthusiasm of a new generation of gardeners. If we can help new gardeners have a successful first experience, they will be back.

JS: I’m a pragmatist at heart — I like things that solve problems. Bayer offers solutions to some of the most pressing challenges facing growers right now. With residual control up to 8 months, Marengo is a key labor-savings tool, especially in spring when labor demands are highest. As for helping new gardeners be successful, our insecticide portfolio of Kontos, Altus, and Savate offers solutions for nearly every growing situation to ensure that plants reach the end consumer clean and ready to impress.

The West Virginia University researcher discusses the latest updates to a trailblazing robotic pollination project.

Yu Gu: This new project is actually our second pollination project. The first project was more about building a proof of concept, building a system that can pollinate flowers. So, we demonstrated that and now we are trying build a system that’s more practical and, eventually, hopefully, go into ag production. There are different aspects of this that interest me and [the team]. One is the impact because, from a pollination point of view, this should be a way to deal with the shrinking bee population. From an engineering point of view, it’s just a really challenging problem for robotics because plants are very different from each other and there are lots of uncertainties in the problems.

YG: The previous version is a proof of concept, so it wasn’t very effective because robots are slow. The concept we used for pollination is really more like a human grabbing a brush to brush the flowers. But using a robotic arm to do that is a lot more challenging and the system is really slow and, with one arm, it’s hard to have it navigate more complex situations like a flower obstructed by a branch. In this newer system, we have a six-arm robot, so one part that’s key is that we can have all six arms run at one time and, we hope, pollinate flowers six times faster. And with the coordination of multiple arms, we can do more complex tasks. That’s what drives this robot.

YG: There’s a lot that we don’t even understand yet. Right now, we are focusing on precision actions and precision pollination - so think about plants being blown with air or shaking the branches so that we can address some of the tougher robotics challenges directly. Once we have the ability to manipulate the more delicate parts of the plant like the flowers, we should be able to take care of the crops in many different ways. We can collect data and we can do localized interactions with the crops. That’s the hope. But we also love our pollinators - we aren’t working to replace the bees. But what we are doing can hopefully pave the way for lots of future applications.