Planting on thick cardboard mulch?

[John in WI]

Hello Folks. Finally spring in Wisconsin, so I'm trying to get a jump on my garden. It's only the second year, so I'm reviewing last years notes and pictures.

The garden plot, from day one, was overrun by a lot of crab grass and other weeds. It turned into an entire season of trying to root it out.

I picked up enough cardboard at the grocery store that I should be able to cover the whole area in 2-3 layers. I would then cover it with more mulch (straw probably, maybe wood chips from the municipal recycling center).

I think for planting seedlings, it would be a matter of cutting a hole in the cardboard and planting. But I was wondering what about planting seeds directly? I was going to do several rows of sweet corn and sunflowers. Can I just stab a hole through the cardboard and insert the seed? It seems like if the sprout can poke through the hole, it would grow fine.

Also, what about small seeds--carrots, beets... Would it work to cut a long slice into the cardboard and plant the seeds in there?

Finally, a friend gave me a roll of heavy black construction plastic. I was thinking to solarize the soil first, then cover it with the heavy mulch? (I also read clear plastic is better than black--but it was free and headed for the landfill).
Sorry for all the questions--I am just really hoping to choke out and kill all of the nasties from last year. I had a serious mess going by fall.

 

[redback]

I'm faced with couch grass in places where it has invaded my garden beds. I won't use glyphosate any more so, like you, I have been collecting cardboard. As much as I hate to admit it, I think a raised bed is the only answer. It will require building 2' (600mm) high walls around the bed and over the edges of the cardboard underlay. You then put 1'6" (450mm) of gravel, soil and then topsoil on top of the cardboard and plant into that.
Unfortunate about the extra cost and effort needed.

 

[Mr_Yan]

I love deep mulch for starting a garden but it's a slow process. Call it a year before you can fully plant in it, maybe 2 with that much cardboard plus a few inches of woodchip.

1 - Look up "Back To Eden" garden for how to work in deep mulch
2 - Never 'till woodchips and cardboard into the top layer of soil. That will lock up nitrogen for a year or two and you'll have to actively rebuild the soil. Don't rototill mulch at all, I don't care what your neighbor or father-in-law says.
3 - The mulch cover will feed and loosen up the soil but plant roots have to reach the soil to grow and grow well.

I don't like plastic in my garden and have no experience with solarizing.

 

[cpp gardener]

The cardboard will work, but you have to cut or leave openings to plant seeds. You would have to make 5” diameter holes for each corn kernel and bigger ones for beets. Or leave a 6” wide gap between cardboard sheets to plant into.
Solarizing works in the Summer to cook weeds and their seeds, but it has to be sunny and hot for it to really work. After you finish, you need to remove the plastic and add mulch onto the soil.
One drawback to the cardboard is that it inhibits gas exchange between the soil and air which is not good. After a season it’s best to mix it with the mulch. Or make some holes in it so it decomposes faster.

 

[redback]

Cutting a hole in the cardboard will result in the weeds growing through the hole and the weed problem returning - won't it?

 

[cpp gardener]

Only in that spot. It should be easy to remove only those few weeds that grow in those locations.

 

[redback]

Only in that spot. It should be easy to remove only those few weeds that grow in those locations.

The weed I have has underground runners (stolons and rhizomes) and will definitely reestablish, even after a year under cardboard. I think this is why raised beds were invented.

 

[John in WI]

I love deep mulch for starting a garden but it's a slow process. Call it a year before you can fully plant in it, maybe 2 with that much cardboard plus a few inches of woodchip.

1 - Look up "Back To Eden" garden for how to work in deep mulch
2 - Never 'till woodchips and cardboard into the top layer of soil. That will lock up nitrogen for a year or two and you'll have to actively rebuild the soil. Don't rototill mulch at all, I don't care what your neighbor or father-in-law says.
3 - The mulch cover will feed and loosen up the soil but plant roots have to reach the soil to grow and grow well.

I don't like plastic in my garden and have no experience with solarizing.

Thank you. I was aware that super-high carbon materials such as wood chips and paper products need to remain on top of the soil. I think Joel Salatain said something about soil growing UP. Build soil by adding things on top. I will look into Back to Eden. I helped my grandfather garden when I was a kid, but am just not doing it on my home (decades later). Sort of makes me wish I had paid attention better! I know, ideally, one wouldn't till at all. But this bed had not been used for 2 years and was fully loaded with weeds.

The weed I have has underground runners (stolons and rhizomes) and will definitely reestablish, even after a year under cardboard. I think this is why raised beds were invented.

Crab grass is bad for that. The only worse thing I've ever personally dealt with is a neighbor's back yard full of Japanese Knotwood. You erradicate it in one place, and 3 weeks later it pops up 15 feet away. It will even burrow under a cement drive way and pop up the other side. To get rid of it 100% would take a concerted effort between all the properties, and most certainly nasty chemicals. But one that stuff establishes, forget it.
I am considering solarizing half of my bed, and letting it cook well into the summer. Then grow on the other side. The bed is the footer for a very old garage that burned down. It already has concrete, about 1' tall, bordering the whole thing. Maybe I could cram all of my plants into part of it, then heavily mulch and plastic cover the other part. I bet in the heat of summer, the volume under the plastic would get extremely hot. Let it go for several weeks, turn the soil, then mulch and recover it. Trying to really make sure any seeds in the soil germinate.
I talked to one of the (nosey) neighbors. They told me the original owner would put horse manure on the soil. From what I understand, horses, lacking a rumen, excrete viable seed along with the manure.
Anyway, thanks for the info and thoughts. I have about 6 weeks to figure out a plan. I just need to whip this thing into shape.

 

[cpp gardener]

Crabgrass is an annual weed that doesn’t have stolons or rhizomes. If your weedy grass has both then you have bermudagrass or Johnsongrass. Both of them are very difficult to control without chemicals, but persistence will pay off, in a few years.

 

[John in WI]

Crabgrass is an annual weed that doesn’t have stolons or rhizomes. If your weedy grass has both then you have bermudagrass or Johnsongrass. Both of them are very difficult to control without chemicals, but persistence will pay off, in a few years.

I just learned, a good friend's neighbor is a real deal Master Gardener, with a strong tendency towards organic growing. I just texted her, to learn first hand about deep-mulching. Another firnd works at the grocery store, and can get me as many of those 4x4 cardobard sheets they use on pallets. My uncle has a pickup, and I can get literal mountains of woodchips, leaves (probably leaf mold by now), and grass/mixed leaf clippings from the municipal place. Another friend keeps 10 cows, and has a 2 year pile of manure I have access to. The big issue, I think, is going to be in logistics. That is a LOT of stuff to move--to get the 8" I read is the minimum for deep mulching. The plan is to add the manure, till and pick whatever weeds I can. Then cardboard, then alternating layers of the other stuff. Straw, leaves, woodchips... It can't hurt. That grass last year was out of hand. The garden is at my mom's house, and hour from me. So I could only tend it one day a week. By fall, you' need a machete to get through it! This year, I'm going to choke those things to death. Dump in all the organic material that it hasn't gotten for a number of years, and generally whip the whole thing into shape. Then in fall, depending on how decomposed the mulch and everything is, maybe till it under again and re-mulch.

 

[Donatello]

John in WI, After reading your initial post, I have in the past started corn in fiberous egg cartons and seed starter medium. Then you can make your hole and plant each seedling after it has been strengthened or hardened out.

 

[MiniOrchardDude]

You might want to use contractors paper instead of cardboard. Well at least where you plan to seed. One layer of cardboard should do the trick. Make sure you over lap the all the seems.

Another option would be to use contractors paper and compost on top where you plan to seed. Then cardboard around the rest. The contractors paper is cheap and breaks down very fast. Cardboard will stay all year whereas contractor paper decomposes rather quickly.

MOD

 

[Meadowlark]

... Then in fall, depending on how decomposed the mulch and everything is, maybe till it under again and re-mulch.

Not a big fan here of cardboard myself, but a huge fan of using cover crops in conjunction with manure compost to build soil and control weeds.

This fall you might want to consider cc to add significant amounts of free organic matter and nutrients while controlling weeds at the same time. Done properly, they can flourish and work for you all fall/winter with almost no attention. The best remote garden tool I know of.

 

[Donatello]

Not a big fan here of cardboard myself, but a huge fan of using cover crops in conjunction with manure compost to build soil and control weeds.

This fall you might want to consider cc to add significant amounts of free organic matter and nutrients while controlling weeds at the same time. Done properly, they can flourish and work for you all fall/winter with almost no attention. The best remote garden tool I know of.

What would be the difference between a cover crop and weeds? We are trying to clear the garden of this weeds/cover crop. Trying to keep anything from growing but what I planted!

 

[cpp gardener]

The cover crop is something YOU CHOOSE that dies at the end of its season and doesn’t reseed to bother you again. Some weeds can be that way IF you cut them down before they go to seed.