Night of the Living Mulch

So a little while back I came across this 2017 Washington Post article about using sedges (Carex) as a substitute for mulch.

Lurie d june 6 13
In the Lurie Garden, grassy plants fill in between the colorful ones.

It’s a variation of an idea pioneered by Piet Oudolf and other naturalistic designers of perennial gardens: use dense, shorter, less showy plants as a foundation or matrix to fill in around those that are taller and more colorful. It serves the same function as mulch: suppressing weeds, keeping the soil moist and cool, and adding organic matter. But it can also give gardens a meadow-like fullness, providing a calm background to the most exciting plants.

Anyway, this article got me thinking.

more nepeta may 19 2013
Catmint covers the ground along the front of the border, but there are still some bald spots in spring. 

I love how this approach has been adapted in places like Chicago’s Lurie Garden. And I agree that it is better to cover your ground with plants than with mulch. But I haven’t embraced either the matrix or sedge-as-mulch idea in my own garden.

The whole matrix approach is perhaps better suited to larger spaces than my 1/4 acre suburban lot. Also, I am a color addict. I just need masses of it, and every year I seem to need a bigger fix.

Geranium white
Wild Geranium in bloom. 

I do cover much of the ground with dense, shorter plants – but not grassy ones – especially along the front of the beds and borders. For example: Catmint (Nepeta) and Wild Geranium (Geranium maculatum). But perhaps this is just a traditional use of plants as groundcover.

For us, grasses are more like specimen plants, like Switchgrass (Panicum virgatum).

DSC_0518 cup plant joe pye weed driveway border front island bed
In most of our beds and borders, the ground is dominated by tall, colorful plants.

But more often, the ground is dominated by taller plants. By early summer, they have blocked any view of the ground – but if you peak under the leaves, you can see the ground is still bare.

Celandine Poppies
Celandine Poppies

One problem we have is that in spring, some of the beds have bald patches. I may deal with this problem by letting the Celandine Poppy (Stylophorum diphyllum) simply take over certain areas. One problem with Celandine Poppy, though, is that by mid-summer it tends to develop a fungal disease that disfigures and then kills the leaves. However, by then the taller plants will have taken over.

Anyway, you may want to read the article. It has a lot of information on sedges that I don’t really talk about.


38 Comments on “Night of the Living Mulch”

  1. Hi Jason … I have been trying patches of living mulch myself but in a very conventional way with different perennial geraniums .. I do like sedges but I don’t have large enough areas for them to really display a profound affect .. but I am working on mini mass plantings ? .. just an idea I have that suit smaller gardens I think .. we really do evolve with our gardens as we age.
    What I started out with, and thought was a good idea when I began gardening … well, that just doesn’t do it for me any more .. but change is a good thing right ?
    Great post !

  2. I really need to do some research into full sun sedges- if that’s even a thing (I suspect it is not). I’ve used California Poppies and Ajuga to a similar effect, but they have a mind of their own and only go where they want (often into the gravel paths). I love this idea, but it can be harder than one might think to find the sort of plant that does this job well AND works with your conditions.

  3. Thanks for sharing your thoughts on the topic and for sharing the link to the WaPo article. I enjoyed reading it. I’m working this year on turning some of my front garden beds into more naturalistic prairie-style plantings, and I did a lot of reading on the subject last summer. I couldn’t quite wrap my head around the concept of the matrix, but your description of it as using the grasses as living mulch clarified it. So thanks for that! The front beds are very well-drained and sunny, so I’ll have to use something other than Carex, but I’ll figure it out.

  4. I’ve thought about this too since I removed, or tried to remove, all the grass in my backyard – clumps of it still recur. But isn’t that celandine poppy the same nasty invasive that readily tries to take over my yard every spring? Between that and the wild ginger I expect to take over every bare spot… I have planted some sedges in the past but I must not know what I’m doing. Maybe I’ll get inspired for next year.

  5. I like the idea but would have a difficult time completely replacing mulch with them. One big issue for us would be bindweed – it’s impossible to deal with when it grows in the grass (hence it simply gets mowed). In mulched areas, we simply keep pulling it up so that it doesn’t get out of control…with a sedge ground cover that would be much more difficult, if not impossible.

  6. In our UK climate I am personally interested in using Chewings fescue grass as a back cloth for plantings.
    I don’t think mulch is appropriate as a description of such planting – the effects can be very different. In certain circumstances underplanting will compete for water whereas true mulches are reputed to conserve water

  7. Hello Jason, despite the fact that I plant very densely, there are still bare patches in the borders and I have been wondering how to cover these up. I take a “layered” approach where you have ground cover, then short, medium and tall plants to create a tiered effect. I think that after I have completed making the borders and have the main plants in, I can then spend much more time thinking about how to fill out the bare patches with ideas like this.

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