Tuesday, February 9, 2010

Ma'am! Put the Landscape Cloth Down and Step Away From the Garden!

I love sheet-mulching and I am here to spread the sheet-mulching gospel.  Seriously, it saves the back muscles and frees up the green bin.  Sheet-mulching is a first step to preparing the garden for native plantings.  It's pretty rare to be starting with bare dirt, free of invasive seeds lying in wait, so sheet-mulching is a way to ensure that the new plants aren't surrounded by the enemy two months after they're planted.  Basically, instead of digging the existing stuff out, it gets smothered  with cardboard or newspaper and topped with a layer of mulch.  They won't know what hit 'em.  Not only that, but as it kills the invasives underneath, the cardboard and mulch break down and amend the soil.  Let's take a peep at a garden I recently converted.


The bare dirt once hosted juniper bushes and that lawn is just too darn impractical.  Water restrictions, weekly maintenance in the warmer months, and the constant stream of fertilizer needed to keep it alive just doesn't make sense. (I'm preaching to the choir, aren't I?)  

So, the next step is to smother the existing vegetation.  Massive rolls of cardboard can be purchased from Monahan Paper or collect cardboard boxes (newspaper works, too.  It might take awhile to get enough of it, though).  Before beginning it's important to check the cardboard for waxy surfaces, ouchy staples or other stuff that won't break down naturally.
Now, the edges of the garden will probably end up with weeds or lawn peeking through over time, so if there's a lawn or weeds, it should be removed along the border.  For the lawn in this garden, I cut through the turf with a utility blade 1' away from the curb all the way down and used the shovel to roll it off.  It wasn't too hard because the lawn was infested with white grub worms (ew, ew, ew!), who weaken the roots.  I used the cut off pieces to fill in depressions in other parts of the garden, making sure the turf was root-side up just as extra insurance that it doesn't try to establish itself again.

Then comes the cardboard.  Setting them down, the pieces need to overlap by 6-12" and can be secured  with U-stakes used for drip irrigation.  Double layering the cardboard can be a good idea if it involves removing ivy, oxalis, or other troublemakers, taking care not to also bury any sprinkler heads.

Once the garden looks like a strange cardboard moonscape, it's time to install the drip irrigation lines if that's part of the plan or proceed to the mulching.  I use shredded red cedar, as it looks "natural", its composition helps it stay in place and not wash away, and most importantly it smells so nice when I'm working with it.  For plants that live in drier climes (like the Salvia apiana that probably hates me right now with all this rain), a gravel mulch might be considered.  A 3-4" depth is mandatory!  Too little will render the whole process useless and too much will bury the new plantings without providing them any extra benefit.  The folks at the mulch place can be pretty helpful when arranging for the delivery.  (especially if the square footage of the area has already been calculated)  It's pricey, but an important investment when you consider the amount of weeding that would need to happen without it.

A less expensive solution is contacting a tree service company, who will gladly dump their chippings, but there's always a risk that it might have come from diseased trees or eucalyptus which has icky toxins that don't mesh well with other plants.  It's aesthetically messier, but hey, it's free!  Either way, mulch is a necessity to help conserve water and amend the soil over time.  (One note regarding native bees:  try to leave an open patch or two for the native bees to tunnel around and make their homes.  Apparently, they aren't fans of tunneling through mulch.)


Next, lay out the plants and start the planting process (Yay!)  With gloves to protect from the splinters, push away the mulch and cut into the cardboard with a utility knife or hori-hori tool.  Plant and you're done!

I'm hoping this little landscape will fill-in in no time.  After planting, I scattered Clarkia and Ca Poppy seeds which will either give the local birds a tasty snack or will provide a colorful filler while the Muhlenbergias and Leymus condensatus' get established. 

Phew!  What a wordy post!  Hope it's helpful and prevents at least one person from buying that horrible black weed cloth or plastic sheeting!


  1. Hello Christine,

    What an excellent post and I love your detailed instructions and photos. So great that there are alternative to plastic landscape cloth (or black plastic, which should be forbidden).

  2. Thanks, Noelle- after tugging on landscape fabric that had a thick layer of weeds growing on top of it, I couldn't agree more!

  3. Wonderful post Christine! We've been smothering some weedy sections, though not nearly on this scale. Since we bought our wood-chipper, we seem to have to have plenty of mulch, and it really has helped to keep the weed patches in check.

    Good point about the bees too. In our bee class we learned that Mason bees don't tunnel, but even they need a little bare dirt as they use mud to seal their eggs in the nests.

    If starting some natives from seed, could I just prep with the cardboard and lay some topsoil over it before seeding/mulching? Some of the seeds we bought from Larner say NOT to start them indoors, but to direct sow outside.

  4. I'd love to hear more about your Mason bee class, Clare!
    As far as seeds, I've just scattered them over the mulch after everything has been planted. However, I am the last person to give propagation advice. My Red Maids from Larner's never showed up (yet, anyway) and I've tried starting Nemophilia twice with no luck at all. And let's not even talk about slugs eating my baby Lupines!

  5. I just love your title! - And sheet mulching. It's the best!

  6. Not only is it a great title, it should be shouted frequently.

    Great job.

  7. Thanks Country Mouse and Nell Jean! I'll shout my darndest.