Keeping abreast of bulbs

Photo courtesy of Jo-Anne van den Berg-Ohms

Consumers are keeping Dutch bulb growers smiling as sales of these crops continue to increase.

“In the last couple of years, we’ve seen an increase in sales of tulips and lilies,” says Henk Westerhof, chairman of Anthos, an organization that represents the flower bulb and nursery industry. More than 1 billion bulbs are shipped to the United States from the Netherlands each year, Westerhof says.

Bulb transactions between U.S. horticulture industry entities are increasing, too. Jo-Anne van den Berg-Ohms, CEO of Van Engelen, a bulb grower in Bantam, Connecticut, says she’s seen an uptick in bulb orders from retail stores and other buyers, including greenhouse potted plant growers.  

“We continue to attract a healthy percentage of clients each year,” van den Berg-Ohms says. “We are extremely satisfied and even enthusiastic about flower bulb sales.” She adds that tulips are still the most popular flower bulb, mostly because of the diversity of colors and relative ease and assurance with which they can be forced. Popular tulip bulbs for forcing include single and double tulips, Triumph tulips and some species tulips.

While tulips continue to far outdistance any other bulbs in popularity, consumers are becoming increasingly interested in minor or specialty bulbs, some of which are forced in greenhouses.

“A continuing trend, and certainly an area we’ve been promoting, is the exquisite vast range of bulbs, not just tulips, and not all forced,” van den Berg-Ohms says. With that said, she adds that there are many new tulip varieties coming out, some of which could be used for potted production in a greenhouse, including ‘Princess Irene,’ ‘Purple Prince’ and ‘Pretty Princess.’

Growing a better bulb

Flower bulb research is ongoing at Cornell University under the direction of Dr. William Miller, director of the Floral Bulb Research Program. Miller’s crew has been studying potted bulb culture for some time now, researching new cultivars, strategies with growth regulators, ethylene’s effects on plants, interactions of specific plant pathogens, carbohydrate metabolism in bulbous plants and physiological disorders.

One area of study and experimentation Miller and his undergrads are currently taking part in is the root development in tulips in 6-inch pots. Miller appears to be taking a cue from the exporters in the Netherlands.

“Within tulips, we tend in the U.S. to grow too many roots,” Miller says. “We plant bulbs in the fall and water them in pretty heavily, then put them in coolers.” He went on to say that sometimes growers don’t pay enough attention to the temperature in the coolers, and subsequently end up with pots packed full of roots.

“It’s astounding how many roots they can have,” he says. “Tulips don’t need that many roots and it can lead to root diseases; the roots dry out. Stress occurs because the roots aren’t surrounded by soil, they’re surrounded by roots and more roots.”

Miller and his undergrads, with the financial support of Anthos, are looking into a way to reduce excessive root growth with tulips in 6-inch pots. They’re conducting an experiment in which they delay the planting date of potted tulips. They cool the bulbs dry before they plant them, then toss them back into the cooler around January for another five or six weeks, during which time they root fairly well. When they brought the bulbs into the greenhouse to finish, Miller asserts they didn’t have the root mass that bulbs planted earlier did.

“What it is, is cooling them on schedule but delaying the planting eight or nine weeks so after planting the bulbs go back into the cooler; they have at least five weeks in the cooler to become established before started in the greenhouse,” Miller says. “We’ve had really good results with that experimentally.”

The cost of dirty water

Another area of research that is ongoing at Cornell is the effect of dirty pots on air uptake in lily bulb production. The dirtier the buckets, the less air uptake. This results in having to clean the buckets more often, which costs bulb-producing companies tens of thousands of dollars, Miller says.

“For growers it becomes expensive to wash the buckets,” he says. “We know if you have a lot of bacteria in the water, it reduces the water uptake and flower size and how long it can last.” Miller says he has an undergraduate student looking at bacteria levels in the water and just how much bacteria forms before it becomes a problem. For now, though, the dirtier the buckets, the shorter the lifespan of lilies, so Miller advises growers to keep washing the buckets.

The beauty of bulbs

At the famed Smith College Botanical Gardens in Northampton, Massachusetts, growers force various species of bulbs for their annual spring flower show that is more than 100 years in the running. They chill bulbs in a cooler that can hold 6,000 pots and then finish them in one of three bulb production greenhouses on campus. The result is a cacophony of color in the spring time, as a host of tulips, daffodils and other spring bulbs flower in the greenhouse and get ready to be displayed in the gardens.

Dan Babineau is in charge of the spring flower show at Smith College. With the help of horticulture students in the program, he pots up thousands of bulbs, including quite a few tulips.

“Tulips are the most tricky because you have tulips blooming outside from the middle of April to the end of May, so the ones that bloom late, such as parrot tulips, need to be potted up early,” Babineau says. He says these need a good two months to grow in the greenhouse, so he and his colleagues put them in the coolers as early as the last week of December.

The biggest challenge overall is fungus in the pots, Babineau says. If you don’t routinely apply a fungicide, he says, problems are most likely to develop. Another problem can be in the bulb itself.

“I planted the same species of tulip in the same area in three different greenhouses and every single one aborted and didn’t flower,” Babineau says. “Pests aren’t too big [of] a problem because we keep the temperatures cool.” He says they usually start the bulbs out at about 50 degrees and gradually work up to 60 degrees. He says it takes a little longer to finish bulbs this way, but he’s noted some advantages.

“If you can grow bulbs cooler and with really bright light, that’s better,” says Babineau, who adds they don’t need to resort to electric light. “You don’t get any elongation and you get stronger stems.”

It’s the Dutch that started the bulb frenzy some 400 years ago, Westerhof says. The Netherlands has the right climate and soil type to propagate the billions of bulbs that are exported all over the world. You might say it’s bulb heaven for anyone in this industry.

“I pinch myself every day when I’m out there in the fields,” says van den Berg-Ohms, who attends professional flower shows in the Netherlands. “It’s just mind-blowing.”

Neil is a horticulturist and owner of Green Industry Marketing. greenindustrywriter.com