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On time, on target

Propagation growers need to be able to consistently deliver uniform, healthy and strong seedlings – and they don’t have long to do so. With many propagation cycles lasting just four to seven weeks, specialists like Ed Thoren at Roelands Plant Farms face constant pressure to optimize every aspect of plant development.

“The plants we’re working with – they aren’t ours,” explains Thoren, head grower at the 24-acre greenhouse facility in Lambton Shores, Ont. “We’re really like their babysitters, giving them what they need so that they’re prepared for the next phase of life.”

Roelands plies their main trade in providing propagation to a range of Canadian and U.S.-based grower clients – each with their own highly specific requirements.

“I would say that we have a good understanding of what growers are looking for in their plants,” Thoren says. “Some want more developed seedlings with flowers, and some want more compacted plants, so they can be grown into their system.”

Photo courtesy of Sollum.

This variability in client need has pushed Thoren and his team to seek more sophisticated growing methods, particularly when it comes to lighting technology. Thoren and his team installed advanced dynamic LED lighting fixtures from Sollum Technologies in the spring of 2025, in a two-acre area of their facility, where they have seedlings in plug trays at high density.

Thoren aims to use Sollum’s multi-spectrum lighting to influence the morphology of their plants and, in the process, make the entire grafting process much more seamless.

“For us, the multi-spectrum helps us ensure that the rootstock is compact and has the most energy. That allows us to make the graft really low, with higher success rates,” Thoren explains. “The scions need a little more stretch just to get above the cotyledons, because we want to remove them when grafting. So, we’ll use the far-red light spectrum to to achieve this and make the grafting more compatible. That was one of the biggest reasons for us switching to LEDs.”

Challenges that drive innovation

The stakes are particularly high when it comes to preparing plants for long-distance transport. Some of Roelands’ seedlings must face grueling journeys to reach their final destinations, which was another main reason for their switch, as dynamic LED lighting can contribute to more resilient plants that can withstand the stresses of transport.

“Some of the plants we grow – like our watermelon seedlings – they’ll go three days in a truck. So, we need to be able to fill that plant full of energy and keep it super-compact to fit in a box so that it can withstand long distances,” Thoren explains. “We’re experimenting with using the heavy blue light spectrum to keep the seedlings compact, so when they come out of the box, those plants aren’t too stretchy or weak.”

It’s these demands and tight timeframes that are leading other greenhouse growers like Thoren to seek out more advanced lighting systems, says Sam Soltaninejad, chief horticulture specialist with Sollum Technologies.

“If those seedlings are stretching more and more, they’re going to get damaged, you’ll have fewer seedlings per truckload and they’ll be at the wrong growth stage to be transplanted,” he explains.

Up until a couple of years ago, he says, high-pressure sodium (HPS) lighting fixtures were the industry standard, but came with a couple of major drawbacks – energy efficiency and lifespan.

“After three years, you need to replace HPS bulbs, and then after five or six years, the entire fixture. So, there is a lot of cost involved,” Soltaninejad explains. “With LED lighting, we don’t have that problem anymore. They are, on average, 30 to 40 per cent more efficient, while the expected lifespan is between 10 and 15 years. So, growers aren’t having to deal with repeated maintenance or costly purchases.”

Excess heat is another significant challenge with HPS lighting.

“Most of the time you really don’t need the extra heat that lighting gives off. While it can be useful in the lower-light months between December and January, it’s an issue for the rest of the year and impacts how precisely you can control crop development,” Solteninejad says.

The science behind spectrum control

For Sollum, “advanced dynamic” means more than the ability to brighten or dim fixtures, Soltaninejad continues. Rather, dynamic LED lighting provides fully customizable control over virtually every facet of the light that’s delivered to propagated plants.

“For every growth stage of a crop, there are very specific light requirements. You can’t just blast everything with the same intensity,” he adds. “That’s why having flexibility and control matters for growing high-quality seedlings.”

Sollum’s fully adjustable LED lighting system allows growers to fine-tune light intensity, spectrum and photoperiod with unmatched precision. Growers can also create and input an unlimited number of specialized lighting “recipes” by crop or specific crop varieties.

“For example, we can create different recipes for the beginning of the propagation phase, for rooting development. At that point, we would want a higher ratio of blue light to red. And then, once the roots are well-developed, we could change to a more balanced recipe for the crop to grow evenly and uniformly,” Soltaninejad explains. “But if you don’t have that flexible lighting system, you’re giving up a huge amount of control over the plant growth stage and morphology by providing the same level of light from start to finish.”

According to Thoren, Sollum’s advanced dynamic lighting helps not only with morphology of the plant, but with the healing process post-graft.

“The plants will spend several days in plastic healing tunnels – and we’ll supplement with low light during that process,” he says.

He notes that the Roelands team performs much of their propagating and grafting from July to the end of August.

“Heat is always an issue in the summer months. Before, when we were running HPS fixtures, they were generating even more heat, which isn’t helpful as those plants are under a lot of stress coming out of the grafting process,” he says. “With dynamic LEDs, we’re able to keep those plants as comfortable as possible while they heal.”

As the darker fall and winter months approach, Thoren says he’s looking forward to exploring the full potential of the Sollum advanced dynamic lighting system – especially when it comes to dialling in plant structure and morphology.

“I’m hoping we can ultimately get to a more compact plant and have far more control over what we’re producing by using those different spectrums,” he says. “I tend to prioritize a smaller, hardier plant that can withstand the shock of being transported.”

Thoren has been working closely with the team at Sollum to grow the area of their greenhouse under dynamic LED lighting.

“Sollum came out and guided me on how to use the lights to our advantage. We found that we could run four fixtures at the back of a bank and use that as a tiny trial area,” he says. “Once we had confidence the plants were going to respond the way we want, we were able to transform the entire zone.”

For more information, visit sollumtechnologies.com and visit Sollum Technologies at booth #2007 at the Canadian Greenhouse Conference from Oct. 8-9, 2025.

Created by Amplify Content Studio, in partnership with Sollum Technologies and Greenhouse Canada