Ideas to keep weeds down in 1"x1" space between concrete

San Francisco, CA

Any easy/cheap ideas to keep the weeds down. The spaces between
the huge concrete slabs are appx 1"x1" and is a combination of very
sunny to very shady area. I was thinking gravel, mulch, or wood strips
( I really don't want to install wood in between).

Help those weeds are regrowing quick!

Thumbnail by sonomagardener
central, NJ(Zone 6b)

I would spray it with weed killer, then after waiting time stated on product plant some thyme or other low growing groundcover in between instead

Greenfield, OH(Zone 6a)

anything you put in there will still grow weeds eventually. The weeds appear to be a grass. I'd just use a weed eater to keep it looking low and trimmed.
The only no maintenance solution would be to fill the gaps with concrete

Magnolia, TX(Zone 8b)

Ummm, does get interesting trying to pull weeds from gravel- or mulch- grass is deeper rooted than most other aggravations, spray first, some folks cover with layers of newspapers- plastic disintegrates with a bit of time- and then is time consuming moving into the trash- nothing is permanent- and why do you have the blocks like that?

San Francisco, CA

Originally there was wood in between the concrete as I found evidence of
this around the edges. This is just a rental place, so I don't know if I can
pour concrete in between

I like the idea of some sort of electric/gas trimmer, that could be useful and
then I could just add the scraps to the compost.

Anyone else?

Hopkinton, MA(Zone 5b)

sonomagardener, an easy solution would be to remove the weeds and soil about two inches deep. Then fill the space with sawdust which depletes the soil of nitrogen making it difficult for weeds to grow again. Sawdust is normally inexpensive. A local lumberyard sells it for about $10 per square yard.


Arroyo Grande, CA(Zone 9a)

Kill the weeds that are there by pulling or chemical means then use a pre-emergent.
There are several granule type products, Amaze or Preen, work well. I use it when I start to see weeds germinating. It lasts three months and I usually only need it twice a year. It doesn't kill the weeds, it stops them from germinating, so if you get it nice and clean you can keep it nice and clean.

San Francisco, CA

I am getting ready for spring here in SF and would still like some more recommendations. I'm not really trying to spray weed killer, because I don't want to use any harsh chemicals, I have a veggie patch nearby.

I think I am going to go with a low ground cover such as thyme like flowAjen suggested.

Thanks everyone and keep the ideas coming....

Opp, AL(Zone 8b)

Thyme-filled cracks is one of those romantic garden notions that seems so easy on the surface but is actually much more difficult, especially if you've got something as tough as grass to eradicate first. If you're renting, you may not want to spend the money it would take to replace that much grass with thyme plants. That would require, as mentioned, excavating the top couple inches of soil throughout all of the cracks to make sure you are removing any grass seeds, and to remove the grass roots. Some grass would come right up in a strip, other grass would have much more tenacious roots that might break off at the edge of the blocks. Grass roots left behind can keep growing. Not sure what kind of grass you have. Once the grass is pulled, the cracks would need to be filled with soil or sand so you don't break an ankle, and give the thyme something to get rooted into. If grown from seed, you would need to be vigilant the first couple years to monitor for other stuff sprouting, to keep it pulled. Not at all unreasonable, but may not be what you had in mind for initial labor and ongoing maintenance.

Besides just trimming this occasionally, dogooder's sawdust idea's not bad. If some of the cracks are fairly deep, you might have good results just packing it on top of the grass. Looks like a great spot for a table with umbrella. Radically increasing the amount of shade would make it hard for grass to grow there, could kill it, at least in that shadow.

Mixing up some quickrete with a little extra water would not be expensive or difficult. That would make it more liquid-like, and just take longer to cure. There would need to be enough of a gap, depth-wise, for it to be effectively thick between the blocks, so would probably need to pull up the grass to do that too. Once you've done that, no maintenance, a 1-time effort.

Philadelphia, PA

I had a similar problem with the weeds popping up around the brick pavement. I bought a gallon of vinegar at the grocery store and poured it straight on the weeds. In a day or two everything was dead. The area I did this to was much smaller and the weeds weren't as high as the ones in your picture. Someone said I may have introduced acid from the vinegar to the plants and that may have done the trick. I don't know if it will work for you but just thought it may be worth a try.

Ayrshire Scotland, United Kingdom

I had a much about the same problem when I removed weeds ect from old fashioned cobble stones found when we first moved here,
I did all the stuff recommended by others above with the exception of weed-killer as I try to avoid them, I found a squad of workmen laying pavers on a driveway and asked them the best way to re-point the gap between my cobble stones, they recommended remove as much soil as possible that has weed roots still in the soil, then in a DRY day, in a barrow, make up a mix of 3 parts of builders Sand TO 1 part Cement, then brush this mix into the spaces between the slabs, use a stiff broom to get it into the cracks between, then use watering can with FINE rose to water this mix to help it set,
I can honestly say, this has helped a good deal with the exception of a few annual weeds but these are easy to pull out.
As I am in a different climate from you (we have lots of rain fall), i would check with the DIY store the best mix for your area as I know it differ's slightly area to area.
Good luck. WeeNel.

Contra Costa County, CA(Zone 9b)

In SF you could have annual bluegrass (reseeds like crazy, but each plant you pull out does not return) or any of several cool season grasses (can return from the roots if not properly removed) or bermuda grass or bent grass (no way to remove them short of herbicide).

To plant:
Remove the weed-laden soil in the cracks.
Fill with good soil, perhaps local soil with soil conditioner added, if you have an area in your garden you can use as a source of soil.

Plant from flats:
SF is very mild, and even the full sun areas will not get very hot.
The areas in lots of shade probably also stay sort of damp.
I would use at least 2 species of plants, perhaps more. Select something that is good in the shade and something for the sun. Let the plants figure out where to draw the line.

Since it is a walking area select low growing plants. Most plants will grow outside the 1" gaps unless there is enough foot traffic to keep them pruned. Even then, be prepared to do some trimming. In our area (I am just a little bit inland from you, and entirely familiar with the plants that will work in SF) here are some ideas:

Elfin Thyme. Other Thyme gets taller, will spread outside the gaps, but is workable.
Blue Star Creeper
Creeping Mint
Ajuga 'Chocolate Chip' or other dwarf
Ornamental strawberry (long stringy runners- some tripping hazard)
Irish Moss
Scotch Moss
Snow in Summer
Chamomile (Chamaemelum nobile, not the herb for tea)
Blue Fescue (Can get a bit big)
Phyla nodiflora
Mazus reptans

Baby Tears
Campanula muralis or other low mat type
Viola- especially V. hederacea
Mondo Grass
Dichondra (OK in sun, too, in SF)

Especially good in wet
Lysmachia nummularia (sun or shade)

Remove weed-laden soil.
Add pre-emergent or not (Good idea to do this)
Add a material called Quarter By Dust, or 1/4 minus. These are any of several almost sand-like gravels with mixed sizes from about 3/8" on down to dust. They will pack solid like concrete, but are removable if the landlord does not like it. Depending on the parent material it may be brown, blue-grey (quarried on Mt. Diablo) or gold. Look in rock yards near you, I understand Broadmore (south of SF) may be the closest, but there sure could be others. I am more familiar with the East Bay, and if you cannot find what you want in SF, then come on over to any of the many stores on this side of the bay.
Pack it in by tamping with almost anything, and water it, then tamp again.

Pike Road, AL

Try a agressive spreader, like sedums or vinca minor

Contra Costa County, CA(Zone 9b)

Sedum does not tolerate foot traffic. The succulent leaves and stems squish. Most Sedums are great in rock gardens, and make good ground covers in fairly small areas, but not in a patio.
Vinca minor is too aggressive for the spaces between the concrete squares in a patio. Also, the wiry stems are quite a tripping hazard. VInca minor is indeed a rampant grower, but is much better in a larger area.

Alexandria, VA

I think it looks nice with the grass and adds character. I'd personally just run the mower over it to keep it short when you cut the rest of the lawn and let it be.

Contra Costa County, CA(Zone 9b)

I wonder how this one was resolved? The original post was a year ago!

Alexandria, VA


Great Falls, MT(Zone 4a)

If your interested in just killing the weeds and don't want to worry about harsh chemicals, try vinegar:

Be warned thought that vinegar will kill all plants, just use it on a calm day and you should be ok.

Post a Reply to this Thread

Please or sign up to post.