Years ago, controlling early broadleaf weeds such as clover was a very hit-and-miss proposition because of our roller-coaster winter temperatures. It can be 70 degrees one day and 40 the next. That makes it difficult to zero in on a warm, sunny day on which a post-emergent herbicide can do do it's thing.
Then, around 15 years ago, products containing carfentrazone came on the market and totally changed the way we tackle weeds December through February. I’m not sure if I can take total credit for the term, but I began referring to them as “cool-season herbicides.”
So, in this week’s Friday Profile, I want to introduce you to the most readily available one on the retail market: Bonide Weed Beater Ultra. You can also consider this profile to be a tip sheet on killing clover – I get lots of email on that subject every day.
The first cool-season herbicide to make a splash in the Houston market was actually Fertilome Weed Free Zone. And while it works well and continues to be available in the area, Bonide has done a better job of marketing Weed Beater Ultra, so it’s usually found in more of the retail locations you hear me talking about.
Before the advent of cool-season herbicides, wintertime broadleaf weed control was pretty much non-existent. That’s because standard broadleaf weed controls that are used in the spring and summer can actually kill St. Augustine and Bermuda lawns if applied at the wrong time of year. Conversely, cool-season herbicides used when it’s too warm can do lots of damage, too. And cool-season herbicides don’t work below 40 degrees, so, 78-40 degrees is the proper temperature spread.
But when carfentrazone-based Weed Free Zone and Weed Beater Ultra came along, the art of weed control in cooler months was essentially perfected. Still, there is a caveat to be respected for these herbicides to work properly. Because most water along the Gulf Coast is so hard, you must add a surfactant the herbicides so the sprays actually stick to the weeds. Without a surfactant, such as Bonide’s Turbo Spreader Sticker, the herbicide will just bead up and roll right off the weeds’ leaf surfaces and into the soil.
It’s also important how the herbicide is applied. I highly recommend spot-treating. Since most herbicides are sold as concentrates, the best tools for spot-treating are pump-up sprayers or hand-held trigger sprayers. I suggest avoiding dial-and-spray or ready-to-spray bottles that you hook to the end of a hose - you can’t be as precise with them. If ready-to-spray formulas are the only types you can find, please use them with extreme caution – limit their use to spot-treatments only. You’ll need to be quick with the on-off switch, because overuse on the entire yard can cause the grass to yellow.
And one final reminder about cool-season herbicides: they are specifically for broadleaf weeds. They will not control “grassy” weeds. But if you have things like clover, you have permission to spot treat with a carfentrazone-based herbicide.