[harveypooka]

I've got a large, dull as dishwater patio that has a lot of weeds coming through. I'm in the process of building some planters to break up the space but I really don't want to re-lay the patio slabs. As a solution I'm considering (gasp!) weed killer.

I've never used weed killer before and I've heard plenty of negative things about them. But just yesterday my father-in-law told me that newer weed killers break down quite quickly in the soil, meaning they're not all that bad for the environment.

So, chat.allotment-garden.org, what's the deal with weed killers? Are they an indispensable tool for the garden or will I lose eco-warrior points if I use them?

[mumofstig]

The ethical bit is your decision
All I would say is that the EU has taken all the really nasty chemicals off the market, so any that you can buy now are 'reasonably' safe.

I would spray the weeds with glyphosate, being carefull that no spray drifts onto flowers in tubs or beds nearby.

[Yorkie]

Welcome to the site.  

If you want to be organic then obviously weedkillers are a no-no.

If you are happy to use a weedkiller then that is entirely up to you - it's a matter of personal choice.

The weedkiller which is often used these days is glyphosate - it is systemic (gets absorbed into the system of the plant, so takes time to show its effects) and inactive upon contact with the soil / area.

You can find it combined with a contact weedkiller so you can see quickly where you've sprayed, in the Resolva brand name.

On paths you can find it combined with other active chemicals which promise weed-free for so many months.  I would avoid using these if you are going to put planters on the patio (risk of absorbing the chemicals through the roots / base of the bots), and/or grass or other plants next to the paths (run-off will kill them plus poison the soil for some time).

I use normal glyphosate on my paths and drive without worrying about my eco-credentials; but then, I don't aspire to be fully organic.

[harveypooka]

The ethical bit is your decision

That's the tricky bit!

On paths you can find it combined with other active chemicals which promise weed-free for so many months.  I would avoid using these if you are going to put planters on the patio (risk of absorbing the chemicals through the roots / base of the bots), and/or grass or other plants next to the paths (run-off will kill them plus poison the soil for some time).

I use normal glyphosate on my paths and drive without worrying about my eco-credentials; but then, I don't aspire to be fully organic.

Any ideas how long the chemicals remain in the soil? I'm guessing however long the weed killer claims it'll suppress weeds?

[Yorkie]

I don't know, sorry.  I'd say that's a reasonable assumption but personally I wouldn't want to plant for 6 months after application to soil for veggie growing.

[Trillium]

On North American glyphosphate labels, there is information that says it's safe to plant veggies 30-60 days after spraying. I'd wait the 60 days just to be sure. for ornamentals, its supposedly good by 30 days. I assume grass would fall into the latter timing.

On all herbicide labels there are phone numbers to call for more information.

As Yorkie says, its not considered true organic practice to spray, but sometimes you need to weigh time and ability against eco-points.

[compostqueen]

I was in my greenhouse yesterday tidying up when I noticed some greenery under the racking. I tracked it back to find the source and it was a bramble that was lifting the slabs which were bedded on cement and the gaps grouted with wet cement to years ago.  The area was cleared of brambles first and we waited for growth to re-appear which it certainly did so we hit it with glyphos. It hasn't stopped it coming back.  I checked outside the greenhouse for live brambles and the only brambles there appeared to be dead. Ha!  They're just kidding 

So I wouldn't rely on weedkiller and would dig out as much as you can by hand if the area is not too huge.. 

[azubah]

I have two problems with weed killer.

Firstly, don't get it on your skin or breathe the spray. It goes through the skin and may not wash off.

Secondly, watch out for drift onto other people's plants. It's not fair to damage other people's plants.

Otherwise, it is very useful stuff in the right place.

[Scotch Thistle]

Best advice I ever got about weedkiller is to use a watering can for the application and notthe sprayer. The sprayers tend to create drift as previously mentioned, while drops from a watering can just go where you put them, generally.

If you want to go totally green though a burner is probably your best bet.

[Yorkie]

I once saw someone trying to kill off marestail with the burner. The only thing that was permanently affected was the lavender bush next to the weed ... 

[Aunt Sally]

I did try a flame gun once 

[Endymion]

We've tried a fairly basic weedkiller on our paving because we're worried about runoff. It seems to be a quick fix but there's always something ready to grow through the cracks again, so we're fighting a losing battle.

We're going to try what we heard on the radio the other day. I think it was Bob Flowerdew who said he pours left over hot water (the end of a kettle, vegetable water and so on) onto his paving to kill weeds. He said the first lot should kill off the top growth and after about three treatments the roots tend to give up.

[Trillium]

I tried the hot water treatment before, and it didn't work. Perhaps Bob's weeds are bigger sissies than mine are 

[Lindeggs]

I've found the boiling water treatment reasonably effective, depending on how well established the weed roots are, how big an area you have to treat, and how far away it is from your kitchen (the source of most boiling water).

As was suggested, if you regularly pour all your extra boiling water into the gaps between the pavers, you can generally keep on top of the problem.

In one area (paved with bricks) I did the boiling water treatment for a while then once I felt I was on top of the weeds I mixed various herb seeds with some sand and brushed them into the cracks, to try to replace the weeds with fragrant herbs.  This has had limited success and I still have to hand-weed the grass etc out, but I've had some lovely herbs pop up too and I don't mind the hand weeding.

I used thyme, chamomile, alyssum and assorted wildflower seeds in my mix.  The thyme especially smells lovely when the bricks heat up in the sun or when you walk over the bricks and squash a bit.

[harveypooka]

I used thyme, chamomile, alyssum and assorted wildflower seeds in my mix.  The thyme especially smells lovely when the bricks heat up in the sun or when you walk over the bricks and squash a bit.

That's a great idea!