Homegrown: Pre-emergent selection must meet garden needs

Can you recommend a pre-emergent for weed control for a vegetable garden? When is the best time to apply it?

— Karen

I have a couple of choices for pre-emergent you can use in a vegetable garden. There aren’t many because almost all of the chemical pre-emergent on the market are not labeled for use around edible plants, they’re strictly for ornamentals.

There are some commercial products with a label for single crop vegetable plantings, but they’re generally not available to the homeowner. The only chemical product for the homeowner I’ve seen on the market is Preen Garden Weed Preventer. The label does have a section for use in vegetable gardens.

As with any pre-emergent, this product needs to be applied before weeds germinate. A good rule of thumb is to apply it when the forsythia are blooming around town.

The Preen also should be lightly cultivated into the soil immediately after application and then watered in lightly. The herbicide in this product is pretty volatile and if you just let it sit on top of the ground, much of it will dissipate.

One thing to remember about any pre-emergent is that they will prevent or impede the germination of all seeds, both weeds and vegetables. What this means is that you should only apply the pre-emergent after your garden seeds are well-germinated (not a very good option since the annual weeds often germinate at the same time) or plant your garden from transplants, not seed.

The other product I can tell you about is an organic pre-emergent called Corn Gluten Meal. This is a natural byproduct of the production of cornstarch and corn syrup and is safe and labeled for use in vegetable gardens.

Water it well after application, then it’s important to allow the garden to dry out for a period after the initial soaking.

It’s not a perfect product. In trials, it has reduced weeds by 40–60 percent, but I guess that’s better than nothing at all. At the very least, it will act as an organic fertilizer as it contains about 10 percent nitrogen.

When you’re ready to plant, rototill the area first and away you go.

The only other option I can give you might be more extreme than you want at this point. That is to not plant a vegetable garden in that spot at all this year and concentrate on eliminating the weeds before resuming the garden next year.

Doing this allows you to use some more powerful and effective materials that will do a more complete job of controlling the weeds now with less effort in the future.

I’ve heard a lot about “weed-and-feeds,” but have never used them. I want to try this on my lawn but am worried about our trees. Will a weed-and-feed harm them? How close to the trunk of a tree can I apply it?

— Ellen

Weed-and-feeds are attractive because they are easy to use. You just spread it out and you’re done. No mixing or spraying is required.

They are safe enough if you use a little common sense.

Be sure to only apply what the bag recommends, never exceed that rate. You might want to lighten the application a tad around your trees or even avoid applying it in those areas. You also don’t want to be using a weed-and-feed all the time. Some of these herbicides can accumulate in the soil and repeat applications can lead to problems.

Dennis Hill is the nursery manager at Bookcliff Gardens, http://www.bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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