I don't know about that but a friend just told me about Preen. First, you have to weed (I know!) but then you put this down and it's supposed to help keep the area weed free for up to four months. I just did this over the weekend, so I can't say it actually works yet - but at this point, I'm ready to try almost anything since we have such a giant island.

Here's the deal.....herbicides/weed killers are not sentient beings and can't tell the difference between a weed and a nonweed! Heck, there's a lot of disagreement about that even among us humans :-)

You have your choices - a broad spectrum herbicide (like RoundUp/glyphosate) that can kill or damage any kind of plant or a targeted herbicide. But even targeted herbicides have limits - they either target broadleaved plants/weeds or monocots....plants that have single blade-like foliage like grasses. And neither can tell the difference between what you consider a weed and what you consider a valuable flowering plant.

Pre-emergents, like Preen, are the most flexible and safest to use around established plants but they do require you remove all existing weeds first. All they will do is prevent new weed seeds (or any other type of seeds) from germinating.

The best weed killer to do what you describe and want to accomplish is YOU with your handy-dandy gardening tool!! No spray can do that.

ok, thanks, thats what I was afraid of.

Yes, dig them out is the safest way. Try doing so after a rain or after irrigation - then it is much easier (except for deep-rooted weeds - they are a pain regardless of soil condition).

To keep them from coming back, consider putting on a layer of mulch. Also avoid tilling or cultivating your soil too deeply as that will bring weed seeds to the surface.