Odd that you have both. As ww said, they thrive under the exact opposites of the extremes (too much water vs. too little water). Sandspurs are an annual and as such die each winter and resprout from the seeds the next year. I won the battle (but it took several years) by digging them out every time I saw one and catching my yard when I mowed (which helped to collect the seeds/spurs). Using a non-selective herbicide probably won't work since you are not removing the seeds (the spurs) and they will just regenerate the next summer. Sorry, but, as with so many gardening issues, you have to get your hands dirty (but it is lagoon friendly!).

Dollarweed, learn to love it.  

It's not worth the herbicide / fertilizer cocktail

that you'll be dumping into the Lagoon

to try and get rid of it.

Sandspur, it's a pretty easily ID'd grass.  

Learn to recognize then dig it as previously suggested.  

As long as you're not getting reseeded from somewhere nearby

it's easy enough to get rid of.  

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Mansion turf herbicide is the best product I have found for dollar weed. Its a granular product you mix a very small amount in a pump up sprayer with a gallon of water and spray directly on the weeds. If used at the proper ratio it kills the dollar weeds and leaves the St. Augustine alone. Do it on a dry day during the active growing months and you get zero run-off. It dries on the leaves of the dollar weed and is absorbed into the plant. This minimizes any impact on the Lagoon. Takes about three weeks to work. You will notice a slight discoloration after the first week. By the second week they will be yellowing. Gone after about the third week. Go to Site-one, formerly John Deere Lesco and talk to the boys.

^that's responsible herbicide management right there

good stuff

 

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