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Using plastic weedmat as mulch for growing vegetables in the Kitchen Garden

Last time we blog-interacted I was talking up the pleasures of cardboard as a garden mulch.  As of today it looks something like this:

It offers a certain rustic charm as the fibres begin their rotting journey.

Sentenced to rejoin the earth from whence they came in some part of a tree.

But cardboard is cumbersome to work with, despite its delights.

You also gotta have the cardboard by dint of keen foraging. Either that or you are buying too much packaged stuff...

So I got to thinking as I was rejigging my backyard into Winter mode.

ANECDOTE

Last Sunday the Misses and I visited a local nursery. We did not buy anything, as we aren't always impulsive. Lovely place. Plants were all of great quality and variety. A succession of outdoor rooms per microclimate put together.

What enthralled me was what we walked on as we browsed: the place was carpeted with weedmat.  you know the black stuff that allows the water and air through but suppresses weeds.

I had worked a lot with weedmat because I put it under our stone paths ten years ago (something I now regret) and we had huge roles of the stuff to play with at the school garden I managed.

I later deployed it as a liner for my milk crates to create a milk crate herb garden. Wonderful drainage -- I've now got something like 25 milk crates in production. The crate acts as a frame for the weedmat.

So using it as a naked carpet covering was a surprise as it is usually used UNDER a layer of mulch.  So I started to experiment with the weed mat I had -- and laid it down to carpet my dojo/gym area. An area where the grass will not grow.

Impressive. Nailed into place with tent pegs. Makes a good surface to bounce around on.

And then I thought...

ANOTHER USE

Why not use it in the vegey garden to protect newly planted seedlings.

Same principle as the cardboard. Just make a hole in the mat for the plant to grow through.

I 'could' have covered a large area with weedmat, but really there was no need.

I only wanted to protect new seedlings.

Talk about easy peasey. Much more workable than using cardboard or paper or even throwing down another layer of mulch to suppress weeds.

All good I thought. So I planted out a few different seedlings.

I'm not planning to leave the weedmat in situ. I carefully cut the holes and will re-use each sheet for after plantings once the mat zone is harvested.

I'm thinking different sizes with different hole layouts so that each sheet is its own template.

Note that you need to cut a + shaped hole so that the plant stem has room to expand and you can get your fingers into the dirt to plant the seedling.

JEAN-MARTIN FOURIER

In a fit of research, I went back and read sections of the market gardeners bible, Jean-Martin Fourier's The Market Gardener.

Fourier  loves weedmat and makes a celebratory case for its use as a quintessential organic gardening tool.

At his farm he lays out weedmat over every  bed once harvest is completed and 2-3 weeks of that suppresses the weeds' enthusiasm to come back. He uses it to protect the soil in Winter (as mulches do) and points out that the mat, being black, is a wonderful way to trap heat in the soil.

He also points out that under weedmat, the soil microbial and worm demographics take off. They love the ambience.

You can see how I've applied the mat to my needs. I've re-used old off cuts  and after laying out the holes and cutting them, simply held the mat in place with some old logs I have kept for unknown needs.

I'll still mulch with organic matter as that's how my garden came into being. Although I won't be laying mulch material over the mat. Since I've gone all green mulchy   keeping the Scurvy Weed tamed takes more effort than my laziness prefers. Indeed, I can prepare sections of my beds by laying down the weedmat a week or so before I plant out my seedlings. Maybe it is best to mulch and manure the bed -- then  cover the new layer of mulch with weedmat as a pre-planting protocol 2 weeks ahead of time.

The weedmat will be a total recycle project over and over again so long as -- and I think this is important -- I use it in small focused lengths.

Covering the whole bed -- something we did in the school garden for the vacation periods -- can be wasteful if you start fiddling with the texture and fibre of the mat by cutting holes into it. Similarly when you cover the whole bed you may get moisture run off  and the soil will dry out underneath if the mat covers the bed in a broad convex shape. Too much heat can be trapped underneath. Similarly, I'm not keen to use weedmat to grow perennials as that precludes re-use.

I am reminded of Square Foot Gardening as a design system I could adapt using weedmat.

To make this approach work, I gotta give deference due to my stabbing stick. (Pictured at left). I loves my stick. I use it to piece the soil and by wiggling it about I can create a hole just right for a seedling without disrupting the local soil life.

Holes in weedmat or cardboard are too narrow to wield a trowel about in.  And when you've finished, lean on the stick to stand up.

If you look at the price of weed mat -- around $23 for 25 metres it's not a bad deal for an easier garden life. Look after it of course. Set aside some things to weigh it down. And have a storage plan for your cut pieces. Hypothetically, you can manage your whole garden by consecutively laying down weed mat to suppress weed growth and reduce your mulching efforts and/or bills.

You gotta add the organic mulch material because that is what creates soil and feeds its life. It's all about break down. Weedmat shouldn't replace organic mulches.

3 WEEKS LATER:June 26th

Here's a gallery update on some of the plantings.

Click on images for enlarged view.

I think that in some cases it is clear that the seedlings planted through weedmat have done better than those in cardboard. I suspect that the heat retention from the blackness is a factor. I'm also lightly clearing the underlying mulch away when planting with weedmat whereas with the cardboard I planted over the organic mulch.

It wasn't as if I did some major clearing -- I just swept the mulch -- both dried and green/growing -- aside with my arm, and plonked the weedmat on the exposed space. Just like slash and burn agriculture within a forest/jungle. Note how undisturbed is the area around the weedmat boundary. This is patchwork gardening using dry and green mulches.

In a practical sense, I suspect the best size for using weedmat like this maybe  an approximation of 60cm by 60cm with leeway allowed for weighted instruments like logs, branches, stones, tiles or whatever. Banana stems are great!

Note that I am planting densely...

You want mat cut to a size that can accommodate around 10 seedlings, I reckon. That way it is easy reach and there is less pull as you stab the holes. With a set number you know how many plants you can expect to harvest. And make sure your + cuts are potentially broad enough to accommodate the different stem sizes of a range of plants.

I think the preferred option is to lay down your mat, secure it temporarily -- with a weight, a tent peg or your foot -- and stab all of the holes through the + holes you cut previously. Then plant your seedlings one by one. Secure two sides so that the wind doesn't turn your mat into a magic carpet.

Don't throw mulch on top because you want to recover and recycle your plastic weedmat -- so you need to be able to find it to recover it.

Voila!

The Milk Crate Herb Garden around the weedmat drill mat Portuguese Cabbage:(Couve tronchuda) Spring Onions: who hate weeds. Okinawan spinach growing feral in foreground.

Spring OnionsBok Choi + Asian Greens in Cardboard mulchOriginal cardboard: RadishesCarrotsRadishes:Daikon

Looking at other weedmat projects I note that all of them I've reviewed use the mat to cover extensive areas. I can't rule on commercial horticulturalists use of the material, but in the kitchen garden I'm advocating an eclectic usage of short pieces for small block plantings of seedlings. I'd use cardboard always, but while the cardboard is organic and will break down like other mulches, it doesn't sit as well on the soil and is cumbersome to plant annuals through.

Paper, on the other hand,  is, in my experience, a Permaculture  fantasy.

Other advocates also create big round holes in the mat, often  by burning (!)  after laying the mat down.  Definitely use the + cut instead and stab your holes  in situ. Seedlings are easily 'stuffed' into the holes you make.

Do not use plastic weedmat for planting perennials. Make sure you often rest the mat zones by re-mulching with organic mulches or allowing the spread of green mulch or ground covers  back over the freshly harvested zone once the mat is removed.

At the moment I have approximately 20 or so mat pieces of different shapes and lengths I  can use for planting out seedlings. I expect those mats will last me for years as the commercial product is remarkably durable with a very good ability to survive relentless sunshine radiation. Paired with using cardboard (for perennials, single plantings, ramblers, etc), I think I'm on a winner. 

You'll note from the images that none of the mats are snug (except for the walk-on drill mat area) -- like they are applied in commercial use. You want your soil and its critter life to breathe. Indeed, that is one advantage with plastic -- as it doesn't collapse onto the soil unless weighted down by another covering of mulch or is constantly walked on. 

Cardboard will lose its structural tension and adhere to the soil  which may not be what you want during the life of an annual vegetable.

What you are applying with weedmat  is targeted shade which is still porous to air and moisture. You are asking your plants to live in a leaky tent with their heads outside.

SAMPLING SOME MORE ACTIVITY: JULY 17TH

 

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Comment by Andrew Cumberland on July 16, 2021 at 14:07

I missed your 2 July post until now. My cabbage are starting to come in now and we are silverbeet lovers here as well. We really are blessed with our subtropical climate. 

Comment by Dave Riley on July 16, 2021 at 0:21

I was outback planting out the last of the seedlings I'd planted in my latest seed raising frenzy. I've over done it a bit such that I'm running out of growing space.

If you watch my last video you'll get a sense of the jungling...but now the patchwork of scurvy weed green mulch and growing 'paddocks' of veges is more complex and  jigsawed.

And everything is thriving!

I'm using my remaining weedmat sections and cardboard to plant out the seedlings by employing the same planting principles I've talked about before.

  1. Clear the scurvy weed away.
  2. Plonk down the cardboard or mat with holes templated already
  3. Stab through the already made holes into the soil to create a growing chamber in the dirt.
  4. Stuff the seedlings through the hole and into the soil one by one.
  5. If necessary, lay a stick on the mat or cardboard so that the wind doesn't lift it.

With the scurvy weed cover, my soil has never been better. With the green mulch pulled back and the soil exposed, it's so alive and wriggling. In some spots I have layers of pulled scurvy weed 15cm high.

Other weeds are a thing of the past. I assume that's good, despite the monoculture. It is certainly very convenient. I need to get down and pull the scurvy weed occasionally so that it doesn't get dominant. But that's an easy job of a few minutes activity. No digging. Just drag and drop.

I still 'mulch' with whatever I can get -- cut Vetiver mostly -- but that's' all part of the  'system'. Historically, this time of year was a mulch drought as the lawns weren't being mowed and I wasn't getting grass clippings. The cold weather doesn't encourage grasses. But with these mats and cardboard, it doesn't matter as any mulch's primary role is to nourish the soil life. That's whenever I get some.

Growing a green mulch like this does turn the whole mulch rationale on its head somewhat -- as it is weedy and invasive. The process has been a learning curve and I've had to junk a lot of old gardening shibboleths in order to accept the feral dynamic. I think with the cardboard and weedmat I've arrived at an intervention that marries synergistically with the scurvy weed--that exploits the advantages I get from allowing the scurvy weed to invade.

Comment by Dave Riley on July 2, 2021 at 9:44

In production, July 2nd 2021.

Of course, harvest is another matter. I've been focusing on what I want to eat and what I have harvested well. Some of this stuff is out of season, but still there may  be a few pickings to be had in time.

I forgot to add pumpkin...Seminole (but that too may be the wrong season). Instead of Cilantro it should be Culantro -- the broad leaved, saw tooth coriander.

And chokoes! I'm drowning in green and white chayotes! And I should have mentioned: leaf celery/Chinese celery, native parsley, pawpaw, and maybe I've missed other plants. I have some other fruit trees but, in my garden, they may comprise a fantasy orchard.

Comment by Dianne Caswell on June 27, 2021 at 7:32

Everything is looking great and so healthy. It looks like you have really got onto a good thing with your weedmat gardening.

Comment by Dave Riley on June 26, 2021 at 10:55

3 WEEKS LATER:June 26th

I've added a gallery update on some of the plantings to the original post. I think that in some cases it is clear that the seedlings planted through weedmat have done better than those in cardboard. I suspect that the heat retention from the blackness is a factor. I'm also clearing the underlying mulch away when planting with weedmat whereas with the cardboard I planted over the organic mulch.

Comment by Dianne Caswell on June 24, 2021 at 18:41

The Cottage Garden Flowers will bring Bees and Beneficial Insects to the garden to Pollinate your Fruits and Vegies & Beneficial Insects will help to keep those pesky ones away.  

Comment by Dave Riley on June 23, 2021 at 22:39

Planted some sweet potato today into and through cardboard...and laid out a mix of cottage garden flowers and Asian greens planted through weedmat.

Practice you see.

I think the business knack with weedmat per my perspective is to use a manageable rectangular or square sizes with pre-cut + and chequerboard intersections. If your mat doesn't have drawn lines, you'll need to mark your + cut holes so they stand out.

I suggest little dot stickers., rather than trying to paint or draw on the black suraface.

Using short lengths of mat is an advantage when locating pre-cut + flap holes when planting seedlings. So lengths of around 60cm x 60cm (approx)   makes practical sense. But then, a limiting factor is the width of your bed and what else may be growing nearby.

I think having x number of precut, same size mats is the way to go. Each capable of 'holding' the same number of plants in the same layout pattern. Easy to store between uses too.

Comment by Dave Riley on June 22, 2021 at 19:09

The weedmat has changed my style. .-- such as it is.

The mat and the milk crates have sent me --once again -- down the rabbit hole.

So I've been busily shifting stuff about and reshaping the route down the proverbial garden path.

They are variables I can play with.

And since the Missus complained -- once again! -- that 'my' garden was too overgrown, I was smitten by my keen desire for conjugal bliss to, at least, 'do something' that was passably 'neat'.

Since my Herb garden drill zone/dojo in milk crate garden (pictured at right) has been such a thrill to do stuff in, I'm thinking I have a contained outdoor utility room worth meditating on.

This time of year the dogs love it because the weedmat surface is warmer than the bare earth or grass(not that I have much of that). And I love it because I can do my hi jinks there as if I'm located in a special place.

I tell ya: popping outback as required and walking from milk crate to milk crate harvesting herbs for dins puts me in Mary Mary Quite Contrary mode.

AND...I give a nod to Dianne for pulling me back to a cottage garden perspective. And I now have the seedlings coming on to prove it.

Of these the most exciting is that awesome bee magnet, Echium candicans, the pride of Madeira.

Comment by Dave Riley on June 20, 2021 at 20:24

I planted out some sunflowers today by simply using a short square of cardboard: cleared a space in the mulch, laid down the cardboard, stabbed it with my stabbing stick, made a good hole by wiggling my stick, popped in the seedling, padded/poked it into place and marked the spot with a bamboo stake.

Then watered in...

The stake not only marks the new planting, but it also prevents the cardboard from blowing away. To hold the  cardboard in place while stabbing and  planting, just put your foot on it. No need for pegs.

For bulk plantings, I' prefer  to use the weedmat. For  single plantings  cardboard mulching as mat will do.

I also re-configured my milk crate Lego garden. The crates are covered with weedmat and filled with garden soil and some manure. While that ensures perfect drainage, I suspect that I don't need special 'potting' mixes because the plant roots perform differently than in a standard potted chamber with solid walls and base.

Despite being contained by 4 thin walls, the soil in these crates remain fibrous and friable. This is why there are so many advantages with using planterbags. Indeed my garden crates are planterbags in a frame.

I suspect that they are more durable because of the crate -- and since I use old weedmat to line them, a lot cheaper. I finf you can lay any old piece of weedmat on the inside walls of the crate -- like papier-mâché -- and the pressure of the soil will hold the wall in place.  Only drawback is that  a milk crate has a volume limit. It creates a very different soil environment than a pot of the same soil capacity.

I used to think the soil would get too hot or too cold, but because it breathes air on all 4 sides and the weedmat is black it does neither.

All my herbs now are milkcrated for growing. While I grow chives in them, I'm thinking I'll experiment with spring onions more than I have. I've never been a pot person, but these crates lined in weedmat work for me. They are a tad heavy. I can lift them, but it's quite a lift when full of soil. So I do recommend a small hand trolley for transporting about.

IF I was starting out again, I'd definitely begin my gardening journey with milk crates and planterbags. Thereafter, expand into garden bed growing. I've never been into 'raised beds' or the complexities of wiking.

All the cut+come+again plants are very suitable for  bags and crates, I reckon. I've never done spuds.

It helps that I am addicted to hand watering -- which means that with milkcrates and planterbags you are only watering soil where it counts.

Comment by Dave Riley on June 18, 2021 at 20:44

So far, this plastic weedmat hack is doing wonders for comestibles in my patch.

The black colour captures heat* and the plants inserted through the weedmat are thriving.  They are doing much better than those planted through cardboard.

It is clear that I've had significant growth in just one week by the seedlings I planted through the weedmat.

Mind you, there has to be a understanding of how the plant will grow and what it's needs may be.

  1. The + cut through the weedmat  is important so that you get 4 flaps that will fold back as the plant grows.
  2. Make sure you cut is generous.
  3. When designing the layout -- most weedmats have square outlines on their surface. I have learnt that the best use of the mat for later recycling ids to cut your + holes on the junction of the squares. That will make the hole easy to find when you plant and later reuse the mat. These images here are not an example of that cut, but looking at it, you can envisage a planting pattern.
  4. That suggests to me that I can plan for standard weedmat lengths to cover any possible seedling. That's up to you and the size of your growing spaces. 1metre by 1metres is good for me, as is 1.5 metres in length and possibly narrower.
  5. Originally I simply plonked the mat onto of my green mulch, but I find I getter abetter fit if I clear the top layer away so that the mat sits more snugly with the earth. That way there aren't caverns or bubbles that could lift the mat in the wind or hide snails.
  6. To plant: after cutting out my + holes I lay the mat down and pin it to the earth with a couple  slim tent pegs. That flattens the surface and offers anchorage so that the mat doesn't shift while I'm planting through it. Once all seedlings are planted, I remove the pegs and use any old lump of wood to weigh the mat down at two ends so that the wind doesn't life it.
  7. If any weeds come up through the + hole, just poke them down. Pulling will only serve to uproot your seedlings.
  8.  I think you'll find that when you come to harvest and finally lift up the mat, the soil underneath will be rich in earthworms and other nice critters.
  9. While the mat is a weed suppressant, the plastic fibre is remarkably porous for water. it won't pool at all. Unlike, what you'll get, with cardboard.

I need to stress that this is not a substitute for vigorous mulching. What you are do ing is renting a patch in your bed to grow a harvest on for the lifespan of the plants. It's checker boarding as you target spots to grow food in while leaving the neighbourhood 'feral'. 

As I wrote above I'd  not  cover a whole bed with weedmat as that's really changing the ecology. Covering a whole bed would be useful to suppress weeds but that's only a 2 week project. Not forever.

Better I think to use organic mulches to suppress the worst of the weeds. In that sense, it forces you to crop rotate your plantings WITHOUT having to create separate beds.. And if you are interested in green mulching you can grow a green mulch, like a legume, next to your weedmat crop.

*captures heart: what happens in Summer?I don't know.It is worth keeping these figures in mind throughout the year.

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