Be careful with weed and feed

I was thinking of using a weed and feed for my lawn, but have heard that I have to be careful around my trees and shrubs. Is there a problem with that? What do I need to do?

— Joy

Lots of folks like to use weed-and-feed because it’s convenient: one application should do it all — you’re taking care of the weeds while you fertilize the grass. While it’s a bit easier, you have to be careful. The herbicide in a weed and feed doesn’t differentiate between the dandelions in your lawn and the rose bush by it (the herbicide goes after ANY broadleaf). So, if your rose bush happens to get some, it’ll kill or damage it just as effectively as your dandelions. We get lots of samples in the garden center every year of plants with herbicide damage.

A big part of my problem with weed and feed is that most all of them contain broadleaf weed killers that are primarily absorbed by the roots of broadleafed plants. It makes sense, I guess. In order for an herbicide to be absorbed by the foliage, it needs to be in a liquid form. That’s why weed and feed products have you apply them to the lawn after it’s been watered, so there are water droplets on the leaves of the weeds so the granule can dissolve into that droplet. Since that can be a somewhat hit-or-miss proposition, weed and feed products have specific broadleaf weed killers that have more root activity than liquid broadleaf weed killers that you spray on.

Personally, I’ve never used a weed and feed in my yard. I believe that you’re better off fertilizing the lawn and just spraying weeds when it’s needed. There are several advantages to fertilizing the lawn and spraying the lawn separately. First, I think it’s a more effective way of controlling weeds. The spray broadleaf weed killers just do a better job controlling the weeds than a weed and feed product can.

Second, it’s much safer for your desirable shrubs and trees as I’ve discussed before. Third, you tend to use less weed killer than a general application of weed and feed over the entire lawn. I will almost never do a general spray application over the entire lawn. Broadleaf weeds tend to be patchy — there are clumps or areas in the lawn that have the problem, while others are pretty free of the weed. Because of this, I’ll spot treat the lawn where the weeds are, reducing the chances of inadvertently damaging any desirable plants I have in the area.

Finally, the upshot is that you generally save money doing them separately rather than using a weed and feed. It’s usually cheaper to buy a bag of fertilizer and a bottle of spray than what it costs for a bag of weed and feed. Yes, it’s a bit more work to do them separately, but I think the advantages outweigh this drawback.

If you do choose to use a weed and feed be sure to follow the directions carefully. Do not overapply the product. Sometimes people think that doubling the recommended amounts will give them double the control. It doesn’t work that way — all you do is spend more money, unnecessarily risk your landscape plants, and potentially reduce the effectiveness of the application. You also want to limit the use of weed and feed products to no more than once a year. Preferably, it would be every other year. These soil active herbicides tend to persist and can build up in the soil over time and cause problems. Finally, only use a drop spreader, which will give you more control over its application.

Dennis Hill is the nursery manager at Bookcliff Gardens, 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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