Is it safe to use pre-emergent herbicides (such as crabgrass preventer) around my established bulb beds? -Helen

The short answer is “sometimes,” because in gardening a simple question doesn’t always have a simple answer! Products that are labeled as “weed preventers” are usually pre-emergent herbicides, which work by stopping seeds from germinating, so it stands to reason that they shouldn’t affect established bulbs (especially dormant bulbs underground). However, that’s not always the case, as a product labeled “weed preventer” may have any number of active ingredients that affect weeds, seeds, and garden plants in different ways. Every product should be evaluated separately to make sure it’s safe.

Corn Gluten: The Organic Choice

Corn gluten meal is a popular organic choice for preventing weeds. Corn naturally produces a substance that suppresses the germination of competing seeds. In addition to its weed preventing properties, corn gluten is high in nitrogen and adds some organic matter to the soil – nature’s own “weed and feed!”

Sold under brand names such as Preen Organic Weed Preventer, corn gluten meal is considered safe for use around bulbs, shrubs, trees, and ornamental plants. In addition, it’s far less toxic than chemical herbicides.

Chemical Herbicides: Check the Label

As for commercial chemical weed preventers, you really need to read the label. Some are safe around all bulbs, some are safe only if you apply before the bulbs sprout, and others aren’t safe at all. Before applying, read the label (and do a little research) to make sure the product is safe.

Examples of common products include:

• Surflan AS is safe around bulbs according to the product label.
• Scotts Turfbuilder with Halts Crabgrass Preventer is considered safe as long as it is applied before bulbs sprout.
• Trifluralin, the active ingredient in Preen Garden Weed Preventer, is also listed as safe around bulbs.
• On the other hand, Preen Lawn Crabgrass Preventer, isn’t recommended for use around bulbs. In this case, the product label wasn’t clear, but the website had more info. Lawn weed products are designed for grasses only and aren’t always safe around ornamental plants, so be careful if you’ve got naturalized crocuses in your yard.

In general, I would use corn gluten meal (or just pull the weeds by hand), simply because I don’t want those other chemicals in my yard. Many chemical herbicides are known to be directly toxic to our health, not to mention deadly to the environment. I’d also focus on enriching the soil and strengthening the desirable plants, because unhealthy gardens are prime targets for pesky weeds.

Further Information

• How to Control Weeds in Your Lawn
• How to Control Crabgrass
• Applying ‘Weed and Feed’ Products to St. Augustine Grass
• How to Target Weeds in Your Yard (video)

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