What Chemicals Are Used on Garden Bulbs?

Follow the path of most tulips back to the source, and you will probably be happy with what you learn. vali.lung/Shutterstock

Nothing promises spring more than a garden full of beautiful bulbs popping out as early heralds of warmer weather. So it's easy to give in to temptation and buy a pack of tulips or daffodils at your favorite garden center. But do those bulbs pose any risk to your garden from being treated with pesticides and fungicides that might escape into the soil?

A researcher at Cornell University says you can put those worries aside.

"In general, bulbs such as tulips, daffodils, hyacinths and crocus that are grown in the Netherlands are not treated with anything before being exported to the United States," said William Miller, a professor of horticulture at the university in Ithaca, New York. Miller knows what he's talking about: He has researched ornamental bulbs for more than 30 years.

Most ornamental bulbs sold in the U.S. are grown in Holland and packaged there before arriving on this side of the Atlantic, according to Miller. These bulbs number in the billions annually. Because they've been pre-packaged in Europe and because speed to market is essential to meet preferred planting timetables, there's neither a need nor time to treat the bulbs after they leave the Netherlands.

The only treatment the most common flower bulbs sold to U.S. gardeners get is an ecologically safe treatment to remove soil-borne diseases and pests such as nematodes, Miller said. That's done to protect U.S. agriculture from any ride-along bugs.

There is one major exception: Lilies. Their buds and leaves are attractive to aphids, so these bulbs often – though not always – get a bath in the neonicotinoid imidacloprid, Miller said. Imidacloprid is systemic, which means the bulb carries it into the stems and flowers to kill aphids and other insects, such as white flies, that might feed on the bulb's vegetative growth or flowers. This is especially important in the greenhouse industry where plants are grown in close proximity, he said.

If you want to avoid pesticides on lily bulbs, look for organic lilies. You can ask about them at your local retail garden center or order online.

Lily bulbs may be pre-treated with insecticide, because aphids love their buds and leaves.
Lily bulbs may be pre-treated with insecticide, because aphids love their buds and leaves. Kazakov Maksim/Shutterstock

From Holland to your home

It's also instructive and may help ease ecological concerns, Miller said, for home gardeners to understand how bulbs are harvested, processed and shipped. For example, bulbs may never touch a human hand until they get planted in your garden.

Here's how that works:

  • In Holland, machines plant bulbs in fields.
  • In July, after the bulbs are grown to shipping size, machines dig them up.
  • The bulbs are then force-air dried to prepare them for shipping. Lilies and dahlias are washed.
  • Each bulb is jointly checked by USDA and Dutch inspectors to make sure they're healthy and free from soil particles.
  • Next, a machine separates naturally produced side bulbs from the mother bulb.
  • The mother bulbs are then sorted by size. Undersized bulbs are replanted or discarded.
  • Another machine counts and packages the bulbs.
  • Packaged bulbs are loaded into shipping containers and trucked to the port in Rotterdam.
  • The containers are placed onto container ships, which sail to ports in the U.S.
  • When the ships dock at Atlantic ports, the bulbs are cleared by customs agents and trucked to distributors.
  • Distributors send the bulbs to various retail outlets.
  • Finally, you open the packages and your hands become possibly the first to touch your prized bulbs since machines planted them an ocean away.

Times have changed

colorful crocuses blooming
Colorful crocuses are one of the first signs of spring. Krzysztof Slusarczyk/Shutterstock

Brent Heath, who with his wife, Becky, operates Brent and Becky's, a 28-acre farm and garden in Gloucester, Virginia, remembers when the process worked much differently.

A third-generation bulb grower specializing in bulbs for public gardens, landscape designers and home gardeners, Heath said they moved their growing operation to Breezand, a village in the Dutch province of North Holland, in the late 1970s and early 1980s. There, they contract with about 50 growers. Located in the Anna Paulownapolder, a lake bed that was drained in 1846, the region is famous for its flower production. The move allowed them to take advantage of Holland's longer days and more moderate climate, which resulted in a much longer growing season than Tidewater Virginia.

"Initially, when we first started going to Holland, we did encounter what we considered a fairly heavy chemical culture in the production of flower bulbs," said Heath. "They were spraying pre-emergent herbicides to control weeds and insecticides to control aphids on tulips. Often there was a strong chemical smell as you walked through the fields.

"We were not real happy about that," he said, noting that, while Brent and Becky's is not certified as organic, they don't use any chemicals in their operation. As an example, he pointed out that Becky has an 8-acre teaching garden built on the Native American principal of reciprocity. "We give back what we take, so our garden is built only on compost and compost tea.

"Luckily," he said, "pretty early on in Holland there was a movement to become more natural. Today, very few of our growers use many chemicals at all." As the use of chemicals has decreased, Heath said he's also noticed that disease and insect problems have greatly diminished from what they were 30 years ago. There are reasons for that: Growers have largely replaced fertilizers with compost, have begun rotating crops and flood-fumigate their fields. The latter actually kills all life in the soil – bad actors such as fungus as well as beneficial microbes – but adding the compost restores that life to the soil.

Heath said the only bulbs he encounters that have been treated with neonicotinoids are lilies. "We've narrowed down the scope of our lilies, and we don't offer as many as we once did," he added. And those come from growers who use no neonicotinoids in their production, he said. Several of their contract growers in Holland specialize in lilies for home gardens rather than greenhouse commercial pot culture, and the Heaths offer these in their catalog.

Machines often plant and package bulbs, so your hands may be the first to touch them in your garden.
Machines often plant and package bulbs, so your hands may be the first to touch them in your garden. Cornelia Pithart/Shutterstock

Growing tips and myths

If you're having trouble getting your tulips to survive from season to season, too much water may be the reason, said Heath. These are high mountain desert plants, and they want to be dry during their summer dormancy. Instead, they are often placed in spots that are irrigated throughout the summer. That makes it easy for a fungus to get into the bulbs and cause them to rot.

Miller wants to set the record straight regarding what he says is another myth about fall bulbs. That one, he said, probably causes as many or more misconceptions about bulbs than any other: some people get an annoying, itchy rash after planting hyacinths. These people, according to Miller, often think the problem is caused by something that's been added to the bulb, but it's not.

It's caused instead by oxalic acid, which is natural to the bulb. Some people are allergic to it. Others aren't.

If you are one of the unlucky ones, or aren't sure, Heath says there's a simple solution. Just wash your hands, face and neck with soap and water after handling the bulbs.

"You won't itch after that!" Miller said.