Have a bad weed problem? Pre-emergents a good solution

I have a lot of weeds that come up in my yard and vegetable garden every spring and it seems like I’m pulling and spraying all summer long. Is there something I can do to help with this problem?

— Jake

I think I have a pretty good solution for you, at least partially. There is a group of weed killers called pre-emergents. These herbicides work by killing the germinating seed without affecting existing plants in the garden. These materials only work on annuals that are going to be germinating later this spring. These are weeds like kochia, Russian thistle, spurge, chickweed, crabgrass, foxtail and the like. They won’t work on any perennial weeds you may have like bindweed or Bermuda grass.

In your lawn, shrub and flower beds, the product we like is Hi-Yield Turf and Ornamental Weed and Grass Stopper Containing Dimension (now that’s a mouthful!). It’s a granule that you sprinkle out and then water lightly in. I’ve used it in my yard and it eliminated 90 percent of my annual weed problem.

You’ll want to apply it right away. It needs to go on before seeds have germinated — once you see seedlings, it won’t work and you’ll have to pull them or spray with a post-emergent herbicide. Typically, our recommendation is to put it down when the forsythia are blooming around town, which is happening now. Don’t neglect to water it in as well. Pre-emergents can be volatile and dissipate if not washed into the soil. Though dimension is much more stable than other pre-emergents, you’ll get better, more complete weed control if you drag the hose out and water it in.

With some annual weeds like spurge that can germinate over a period of several months, you’ll need to put down a second application in six or eight weeks.

All this works fine in your flower and shrub beds. The problem arises when we’re putting things down in the vegetable garden. Almost all of the chemical pre-emergents out on the market (including dimension) are not labeled for use around edible plants, they’re strictly for ornamentals. The only homeowner chemical product I’ve seen in the market is Preen garden weed preventer. The label does have a section for use in vegetable gardens. However, the herbicide in this product is pretty volatile and you’ll need to water it in well after applying.

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

The only 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 corn starch and corn syrup and is very safe and labeled for use in vegetable gardens. Water it in well after application. It’s important to allow the garden to dry out for a period after this. It’s not a perfect product — in trials it’s reduced weeds by 40 percent to 60 percent, but I guess that’s better than nothing at all! At the very least, it will act as an organic fertilizer — it contains about 10 percent nitrogen. When you’re ready to plant, rototill the area first and away you go.

Dennis Hill is the nursery manager at Bookcliff Gardens, 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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