Modified Lasagna to kill grass around tree & remulch?

Algonquin, IL(Zone 5a)


We have two River Birch Trees (about 7 years old) that originally had hardwood mulch around them. Over the past couple of years the grass kind of took over & we would like to reclaim the area so we can remulch. Birch trees have lots of shallow feeder roots so it's been difficult trying to pull out the grass.

I'd like to try covering the area with newspaper & used coffee filters/grounds, plus some compost & then hardwood mulch. My hope is to kill the grass & nourish the trees at the same time. I don't want to use weed blocking fabric if I can help it because I want the nutrients from the mulch to get to the trees.

I don't know if I need to cut holes in the newspaper to allow water through. I definitely don't want to hurt the shallow feeder roots.

Have any of you had a similar situation? Has anyone tried a similar method?

I'm interested in any and all suggestions.

Charlotte, NC(Zone 7b)

If you Google "Mulching Trees" you'll find some good tips. The one I think is the most important is to not put mulch up against the tree's trunk, giving it a "volcano effect"

Algonquin, IL(Zone 5a)

Thanks HoneybeeNC - I'll check it out.

I absolutely agree with you on not mulching too close to the trunk. A lot of people don't realize all the damage it can do (rot, insects, disease & more).

We originally had mulch around these trees but after a while the grass started to move in and eventually took over. Because of the shallow feeder roots that River Birch has, we've found it very, very difficult to pull out the grass without harming the tree roots.

I'm considering just putting mulch on top of the grass or even using landscape fabric for one season with mulch over it. Then removing the landscape fabric at the end of this season or the beginning of next Spring.

I'm not sure if my original idea of newspaper is a good idea so I might just scratch that thought.

Charlotte, NC(Zone 7b)

nutsaboutnature - I think your idea of adding mulch over the grass might be the best solution. The trees' feeder roots should grow into the mulch and claim the area back from the grass. Keeping air available to the surface roots is the most important consideration.

I would cut the grass as short as possible before adding mulch. (Got goats?) LOL

Algonquin, IL(Zone 5a) goats, HoneybeeNC, but cutting that area real short is probably a good idea.

I'm leaning more & more toward just the mulch alone idea . . .It would certainly be less work!

Thanks for your suggestions.

Everett, WA(Zone 8a)

Maybe corrugated cardboard to keep down weeds - that has to be more effective than newspaper. From reading, advocates of the Lasagna method don't drill holes, they let the water seep through.

Maybe you could taper the mulch layers to be thinner in the 6-12" surrounding the trunk, down to just a ring of bare cardboard in the few inches right around the trunk. Maybe double or triple thick cardboard, right around the trunk where there is no mulch!

Maybe add a narrow ring of bricks RIGHT around the trunk, laid flat and not quite touching the trunk, but hiding the cardboard. If you have an angle grinder, maybe cut corners diagonally to keep the cracks as narrow as possible. Or go whole hog and mortar that ring of bricks! Then the only grass that comes up will be hugging the bark.

Umm ... if you mortar the bricks together, leave enough room for the trees to grow!


This message was edited Jun 6, 2011 7:32 PM

Algonquin, IL(Zone 5a)

Thanks for the input, RickCorey_WA -

My biggest concern is whether anything as heavy as corrugated cardboard would suffocate the feeder roots of the trees. I know it's used in Lasagna gardening & had originally considered it for that reason. I haven't found any info yet about anyone using it under trees, though so I'm still undecided.

Everett, WA(Zone 8a)

MAYBE you could cover about 1/3 of the area that you want to mulch with heavy cardboard.
Like wedges opf pie, or a checkerboard. Each spring or fall, move the cardboard (or add new cardboard) to cover a different third. If the grass is easily shaded out, maybe move them every few months.

That still ought to let in enough air, and might reduce the amount of grass or its vigor.

If that still seems risky (suffocating roots, which I know nothing about), you might lay down a thin layer of coarse bark chunks or wood chips first. Cardboard on top of that. The coarse chips will definitily stay aerated, and the cardboard might shade the grasss enough to deter it.

Maybe find something that can compete with grass on top of shallow tree roots ... pachysandra ?

If these roots can turn and grow upwards, I wonder if there is any mulch or cultural practice that would let the tree roots out-compete the grass? Frequent short mowing, witholding water, liming, lots of sand, extra-deep wood chips frequently applied, adding soil in some season when the tree roots are active and the grass isn't ...

... growing squash or pumpkins in contianers so that the leaves smother the grass ...

(I think you already ruled out goats.)


North Ridgeville, OH(Zone 5b)

What about renting a flame weeder?

Thumbnail by PuddlePirate
Algonquin, IL(Zone 5a)

Thanks for all your suggestions. I think I'm just going to lay down some newspaper or cardboard with hardwood mulch over the top.

I've read that its best if you soak the newspaper/cardboard in water first. If I think about the times we've left a pile of leaves a little too long on the tends to kill the grass. So I'm kind of thinking along those lines. I'd rather do too little and have to redo it than do too much & harm the tree roots.

The temperatures have been unbelievably high here for this time of year & its been hard to do a lot of yard work for the last week or so. Hopefully we'll have a bit of a cool down & we can get started again on some of these projects.

I appreciate the link PuddlePirate, but I don't want to burn the grass off. Even if its a slow process I'm more comfortable with just remulching with maybe a little paper or such underneath.

Thanks, again everyone!

Everett, WA(Zone 8a)

The combination of lots of newspaper, wood chips, and a blow torch would be BOUND to kill off that grass ... oh, you didn't wnat to burn the tree and house down.

But it would have worked GREAT!


Charlotte, NC(Zone 7b)

Corey - you're a hoot!

Everett, WA(Zone 8a)

Looney R Us.


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