Preventing Weeds (Garden Clutter) with Cardboard

 

I’m starting my third gardening season since moving to “the country” and I’m hoping to do things (at least a little) better this year. Last year, the weeds got out of control and I ended up giving up. I’d heard about putting down cardboard to prevent weeds, but was worried that I’d missed the window. I took advantage of my newsletter list to crowdsource advice. Many of you asked me to share what I learned, so here you go!

(Also, I’m using my affiliate links to products y’all recommended.)

My Question:

 “I have a question for those of you who garden. I saved (too much) cardboard to cover my garden to help prevent weeds. I had thought I’d get it put down in there over the winter but never got that done. Is it too late to put it out now when I’ll likely start planting within the month? Would the cardboard need to decompose first? Is there a way to use the cardboard for weed prevention this late in the game?”

Your Answers:

The VAST majority of you said to use cardboard for weed prevention at ANY time, and that it works great. I’m about to try it in my front flower beds, so we’ll see what happens! I’m including lots of different answers! Many of the answers repeat tips, but also share a little extra helpful information.

(If you have additional expertise to share, please do so in the comments!)

“Just like decluttering, you always can jump in and do something. With the cardboard, yes, you can use it, but you’ll want to dump compost, garden soil and/or mulch over it when you lay the cardboard, so it looks nice. If the layers of compost, garden soil and/or mulch are thick enough to suit your preference for planting, you can punch a hole when you plant the seeds. Alternative to the above is to place the cardboard down before weeds start popping up (warm weather = weeds) and just weigh the cardboard down so it won’t blow away. The sun and rain will begin decomposing the cardboard until you can get it covered. In the meantime, the cardboard will prevent weed seeds from getting the sunlight they need to grow. Depending on your time, resources, you can place that cardboard right away! Option 1 will look tidy and Option 2 still will prevent weeds from having what they need to grow. PS It is difficult for a gardener to have too much cardboard– remember you can layer it in two thicknesses in areas that have very stubborn weeds. You are trying to prevent sunlight from energizing those weeds!”

“In general, smothering weeds with cardboard is a good idea at any point. The cardboard will eventually decompose, yes, but you want it to smother the weeds first, before it becomes compost! I have done this while the weeds are full-sized and extra annoying to deal with in my flower garden, with great results. I lay the cardboard down, dump some mulch on top (at least 2-3 inches), and plan to put more on top of that layer as time goes on. Yes, small weeds will grow on top, but pulling them as they come up won’t be as bad as trying to clear what I had been dealing with underneath…Anyway, my favorite method related to any of this comes from a book called Weedless Gardening by Lee Reich. The steps he describes in it can get mighty complex, but basically, he recommends smothering the weeds/grass with cardboard rather than digging at all, and then adding layers of dead leaves, mulch, dirt, etc. to create new soil to put your plants into. Disturbing the soil can “wake up” the weed seeds in the ground, and give them a chance to grow now that you’ve re-introduced them to the light and water at the surface. I like doing this in small doses, since, as you know, a harvest can get pretty overwhelming if you go too big on the front end with gardening. The first 2 years I did the weedless gardening method (creating my own beds on top of a layer of cardboard with leaves and mulch and bags of compost & soil) were amazing!”

“Just cut an X shape into your cardboard where you want to plant your plant. Lift the pointy bits of the cardboard created by the X and dig underneath. This works better if your ground is soft and you have small seedings. If your plant doesn’t fit, cut a bigger X shape.” 

“A master gardener taught me the cardboard method (called “sheet mulching”).  You can do it anytime of year (after the snow is gone).  You spread any kind of mulch over the cardboard and just cut holes with a knife where you want to plant.  If you are spreading seed, just make sure you have a few inches of mulch (you can sprinkle compost or soil over or under any mulch).  The cardboard will decompose pretty quickly, composting under the mulch.”

“Never too late to lay cardboard on top weeds, emerging weeds, or bare ground, It blocks the sun so weeds die, or don’t germinate. In walkways, it can be covered again as it decomposes.  I’m a Master Gardener since 2003.”

“Cardboard can be put down any time. Just make sure you remove all the staples and tape. You might want to mow down the weeds first. Cardboard doesn’t stay down on its own. So you need mulch to cover. The idea is to starve the weeds from sunlight. Some people do go ahead and cut holes through the cardboard to plant anyway.”

“Absolutely, lay the cardboard!    Spray it good with the hose to make it a little softer to walk on.  And if you have anything finer to layer on it, such as sawdust, grass clippings, leaves, do that throughout the year as it becomes available.  This will make it easier to walk on, too, and as it all slowly decomposes, you’ll be keeping it built up, keeping the weeds down. And if you want, if the stuff you use is not from toxic sources, as the layers decompose, you can shovel that into the garden beds to build up humis in the soil, ‘sponge capacity.'” 

“Never too late! With my home garden I use cardboard covered with mulch or leaves by the fence line (I’m getting too old to be climbing in between the privacy fence and the hurricane fence).  At school with my students, we used cardboard and/or thick newspaper to prep our new garden. I’ve done it in March and August and months in between. I’m in Michigan, so your timing might be different, but no need to worry about too late. If you need to weed first, do so, but for some scenarios you might not. I generally do and use the cardboard as a post weed preventative measure, but I have seen people put it directly over plants/grass when planning a new space. In that case, make sure it is thick and overlapping and covered with some nice compost or topsoil. (I am lucky enough to live in a city that offers free compost! Yay!)”

From New Zealand, “I’m not in your climate Zone, however I do know that cardboard is an excellent weed suppressor in mist climate zones, combined with adding mulch on top of the  cardboard once it is laid out on the garden. The soil can still breathe and so stays healthy but the weeds cannot get going. Gradually the cardboard and mulch break down, as in the ancient process going on in forests since time began. It is beautiful nature at work in the way that God has created.”

“Yes, we have used it and no, it’s not too late. I live in San Antonio & we’ve used cardboard for weed control. It breaks down over time (1-2-3 years) after in place. It does not allow water through like weed matting does. So anywhere you put it will be a slow seep through (may be good or bad depending if you want to water roots, say, of a fruit tree). We have used the free service Chipdrop (from tree trimming company) to get a big load of wood chips to place on top the cardboard.  Now we just use a deep layer of wood chips without cardboard for weed control on pathways. And the wood chips was huge benefit during our years of drought here.”

“Not too late to use cardboard. Can be done any time of year. Key is to get it very wet before covering with mulch. I have cut holes for larger plants and put in a stake there to mark it if planting soon. If planting seeds you could try leaving a small gap between cardboard (mark location) and put seeds in rows between them.”

“You can put the cardboard down at any time. Just cut a hole through it to put each plant in the soil. Make sure you water it well. That will help the decomposition process and also help it reach the stage where it is acting as a mulch and keeping the soil. Cool and moist.”

“Hi Dana! If you’re starting your garden from scratch, you should put a weed barrier down first. That will help much better with preventing weeds. They usually come in a very wide roll, so you can even go up the bit on the sides of your planter. Then you can use cardboard, etc. which will decompose over time. ” 

“You may have some weeds popping up by the time you plant. You can roto-tiller them in, or you can just lay the cardboard over them. Plant soon, though. Don’t let those weeds get big and strong, or they will find their way around the cardboard. PS—  you do not want the cardboard to decompose first. It is not compost, although it may contribute a tiny bit that way. You want to keep it solid and impenetrable so that the weeds can’t get through.”

“About the cardboard. I tried this option to kill a lawn… It’s been almost two years and the cardboard has just started to decompose. While weeding, every time I’m out I end up picking up some pieces and tossing them. But I’m in Northern California. We only get rain consistently for about 3-4 months. I’ve never used cardboard for weeding specifically like landscape fabric. If you just want it as an under layer to prevent weeds it can be used anytime, but decomposition can take some time.”

“I actually just use the cardboard for my paths/non-planting areas… and I put mulch over it.  It never breaks down in time for me, or should I say I never get the stuff put down in time!”

“Literally just prod a hole big enough for your plant through the cardboard and settle the mulch/compost back around the stem of the plant, but don’t cover it. The cardboard will starve the weeds of light, but your plants will be able to push its roots down into the ground.”

“Not too late to use cardboard. We used it the day before planting by laying it on the dirt and covering with a new truckload of compost (it was time!) but below is another option for you! The cardboard will eventually  decompose, but what you can do is plant your garden like normal, and then lay cardboard between the rows. Spray with water to help it stay flat and mold to the earth, then you can cover with pine straw or mulch if you want (it may be slippery if not!). We just took a wheelbarrow into the woods behind our house and gathered up straw and used it. Use what you have! The cardboard significantly cut down on weeds!!”

“Put that cardboard down NOW. It won’t prevent any weeds that have already sprouted but should prevent them from getting huge.”

 “You can use the cardboard between the rows of plants. If they are big pieces it would probably be easier to use them between plants like tomatoes that need big spacing. You will have far fewer weeds using it! I usually use newspaper and straw but cardboard would likely work longer!”

These weren’t fans of using the cardboard now:

“Do not put cardboard down now. It will shade the soil and keep it cool, when you want it warm to germinate the seeds. As soon as the weather really warms up and your young plants are well established, is a good time to lay out the cardboard between the rows. Keep it a few inches away from the plants. I really like cardboard for mulch, because it is solid, yet biodegradable.”  

“I’m in zone 7B and kept one layer of cardboard on my raised beds for just over two months.  It never decomposed; and when I finally got embarrassed over how bad it looked and removed it, it hadn’t killed any weeds either.”