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How to kill weeds but not plants

Gonzales, LA

I know this is probably asking too much but is there some product that will kill weeds but not my plants? I know I have heard someone talk about such a product but did my ears deceive me? If there is such a product, which do you recommend?

Also, most of my flowers died this winter so I'm almost starting from scratch in my flowerbeds. So, what's a good way to start fresh and apply something that will help prevent weeds from the start?

Thanks in advance!

Dublin, CA(Zone 9a)

If your weeds are grasses then there are weedkillers that will just kill grass but not other plants (there are also ones that will kill other plants but not grass, but that won't do you any good except in your lawn). But if the weeds aren't grasses then you're stuck with hand-pulling or else careful spraying or applying with a paintbrush to make sure you just get the weeds if you've got desirable plants in the area.

Since it sounds like you're starting from scratch, if there are already weeds there but no plants then you can spray whatever you want since there aren't any plants to kill. Then once everything's dead, you can plant new things. If you don't like chemicals, you could also try the lasagna gardening approach where you cover everything with some layers of newspaper and then mulch over the top--the newspaper will smother the weeds.

Or if you don't have any weeds now but are anticipating that some will sprout soon, you can apply a pre-emergent herbicide. This will stop seeds from sprouting but won't affect plants that are already there. However...if you were planning to start from scratch by planting seeds the pre-emergent will stop the seeds you want from coming up as well as the weeds. But if you're starting from scratch by buying small plants from the nursery, then the pre-emergent can be helpful. Note though that it only helps with annual weeds--if there are perennial weeds that are coming back from the roots you'll have to use something else for them.

Gonzales, LA

Thanks so much for your reply! You definitely answered my question and, honestly, I'm not sure what I'm going to do. I have a big bed and the winter killed everything but the camelias. I expect some of my perennials to come up from last year but I pulled the weeds by hand so mostly just have soil and the camelias left right now. I will probably plant nursery plants this year instead of seeds because it's more immediate gratification. So, I'm thinking I can spray the pre-emergent on the soil and carefully spray something else to kill the perennial weeds, like you said. What I'm wondering now is how long do I have to wait to plant the nursery plants so the weed killer won't kill them?

Am I making sense? I feel so ignorant in this department. I like the newspaper idea but I do want to give some of last year's perennials a chance to come up, even though the weedkiller will probably kill them anyway.

Thanks so much!

Dublin, CA(Zone 9a)

Things like Roundup will only kill the plants you spray it on--you could plant other things in that bed right away. And if your perennials from last year haven't come up yet then it won't hurt them either. The pre-emergent keeps working for a while so if you want to start some seeds you'll have to wait a while after you apply it, but if you're planting plants instead of seeds then you can do that right away too. The pre-emergent won't affect last year's perennials either.

Ayrshire Scotland, United Kingdom

As you have done a lot of hand weeding AND you are expecting your Perennials to sprout any time now, I would try at all costs to do without the weed killer stuff, you need a very calm day for the use of weedkiller's as the spray gets blown in all directions with the slightest breeze, or as Ecrane said, use a paint brush and only paint the killer onto the weeds once they have emerged, annual weeds are normally easy to get rid of either with as hoe or hand, perennials are tougher, and IF you break the roots as you pull, they grow back tougher than ever, I would hoe / weed and then cover the area with about 2/3 inches of mulch like compost, wood chip / bark etc, it;s safer, looks good and will compost down into the soil after a couple of years, hope you have some luck. WeeNel.

Hamel, MN

An easy, time saving way to do Roundup on just your weeds and not your plants!

Take a half gallon plastic milk jug (empty obviously) and cut out the bottom, so you have a handle, the open spout, and a large opening at the bottom.

Then take this plastic 'funnel' around to various weeds when you need to spray a herbicide such as Roundup, put the jug over the weed, and spray through the hole in the top. It will contain the spray and drift so that it goes on JUST your weeds, not on your plants; plus it is really quick and easy to use.

I have a lot of weeds that spread via rhizome (underground) and Roundup is the only thing that even remotely affects them. Pulling, hoeing, cultvating - they all just make the weeds angry! So I've gotten good at spraying amongst the plants.

Gonzales, LA

Great ideas! Thanks so much for all of your input. I pulled most of it up by hand so I'm going to put the pre-emergent and may spray Roundup in the "weedier" places where I know they have roots and keep coming up the most. Will the roundup reach the perennial roots?

And when you guys mention using the hoe, does that mean you use it to break up roots and then pick them out by hand? I'm just so frustrated because I pull all of these weeds up and pull up as much of the root as possible but I know there are extensive roots still there.

Oh, and I'm definitely going to mulch this year.

Dublin, CA(Zone 9a)

Roundup works best if you spray it on foliage--I've had some luck when there's a big stem still sticking up above ground and I spray on that immediately after cutting off the top of the weed, but it's designed to work when sprayed on foliage. If there's nothing showing above ground and you spray it on the soil I don't think it'll be very effective. So you may need to wait until those perennial weeds sprout up again and then use one of the suggested techniques for how to get Roundup just on the weeds and not on your plants.

Gonzales, LA

Gotcha! Those are the details that show my ignorance about this whole gardening thing. Thank goodness for all of you!

Thanks! I think I have some good ideas now!

Benton, KY(Zone 7a)

ecrane3 is correct, Roundup is for foliage, and has little to no effect on anything in the ground. I think it prevents photosynthesis in some way, so the plant dies. You should use it on the green parts of a plant, or the freshly cut stem of something that is woody. It won't harm roots or ungerminated seeds.

Gonzales, LA

Ok, so pardon my ignorance...I just bought some Roundup that says it kills the roots and prevents new weeds. Is that true? If so, how will it not kill the roots of my perennials that haven't come up yet?

Dublin, CA(Zone 9a)

I would take that one back and exchange it for the regular Roundup. The extended control one that you got is fine for driveways, gravel paths, etc where you don't want anything growing but I wouldn't use it in a bed where you're planning to plant things shortly. It has an extra ingredient that sticks around for several months to prevent things from growing there. They even say on their website not to use in an area that will be planted or seeded in the next 4 months

Gonzales, LA

Ok. Thank you. Pardon my ignorance about all of this and thank you so so much for all of your help and advice. It's starting to make sense now.


Latrobe, PA

Round up is made to be absorbed by the green of a plant and move through the whole plant and kill everything even the roots! Round up will kill a whole field of weeds that have emerged hen ou can plant right through the weeds. Leave the weeds as a compost! The problem is once you make a hole any seeds in that hole will still grow but not nearly as many!
Attrazine was designed to kill only certain grasses but not corn! There are vine crop poducts that will not hurt pumpkins of or other vine crops. They even make mixtures that are not liquids but mixes like sawdust that you sprinkle on a row of vine crops!
Double digging helps. Dig the top 10 inches of soil then use the bottom layer on top of the 10 inches you first took off! I usuallu add leaves on top of the first layer and top the leaves with the bottom layer. Its almost like composting your top layer of soil and covering it with the dirt 10 inches down. Very little weeds 10 inches down.Also if you strain the top 6 inches that you put on top of the surface dirt you turned over you will have a great garden even for carrots!

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