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.
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.
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.
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).
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.
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.
gardeninacity 
I have a perfect bed for sedges, but I’m assuming they need to be trimmed back either in the fall or spring, and I’m looking for less maintenance. But, I read the very interesting article, and I’m going to do a little more research. Thanks for the info.
They generally do need to be cut back once per year.
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 !
I’ve done “mini mass plantings” inspired by big drifts in much larger gardens. Success has been mixed, to be honest.
Jason, I just love the title for this post.
Thanks. Another good possibility was “The Million Man Mulch” which sounds pretty good though it makes even less sense.
Thanks for the info. That top photo is a beauty.
Thanks.
Just heard Roy Diblik at a symposium here on resilient landscapes. Definitely an anti mulch group. I love Carexes but they won’t stand up to being overshadowed by big plants too much.
Some are much more shade-tolerant than others, I think.
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.
Not knowing where you are or what your situation is, I don’t know whether white-topped sedge would do, but it is happy in full sun. It’s a terrifically attractive plant. I saw the page noted that it will work in gardens if kept watered.
Thank you for the suggestion! That is a beauty, but I’m notoriously demanding of my plants and I’ll never keep it watered enough to be happy. I might have to stick with Prairie Dropseed instead!
Check out Copper Shouldered Oval Sedge at Prairie Nursery!
I will! Thank you!
Very interestig post… I agree with the above comment (Cortney) it is quite hard (in our climate ) to find the right plant that does the job well.
Not sure if there are native Sedges in Australia.
Sedges, especially Pennsylvania sedge (Carex pensylvanica,) grows naturally here but I can’t think of a place where they grow so thickly that there aren’t some bare spots between plants. Maybe this ankle high plant would grow more thickly in a garden with care, but it doesn’t seem to do so naturally.
Good point. I will have to see how they do in our garden.
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.
There are some Midwestern Sedges that like full sun and tolerate well-drained soil. You might check out Long Beaked Sedge (C. sprengellii).
I love the idea of living mulch but am not succeeding at it.
I know what you mean. It’s an attractive concept but hard to translate into reality.
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.
Celandine poppy can spread by seed pretty aggressively, but it’s not hard to control. I’m happy to see the Wild Ginger spread. Again, it’s not too hard to control.
I agree that smaller spaces aren’t really suited to huge mass planting in Piet’s style, but I think your Nepeta is doing exactly the same job.
I think so.
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.
I think in vegetable gardens it’s not a good approach. As for bindweed, I know what you mean. The best option seems to be to keep cutting them off at the ground level.
I would not feel right about using sedges. They are related to too many invasive sedges and other weeds.
However, there was a sedge (that I can not remember) that my great grandfather told me about, that was very good as a soil amendment, even when green. He cut it and brought it to his home garden from the marsh across the street from his foundry in Alviso. I really should find out what grew there back then.
Maybe that’s a California thing, I don’t make those associations.
Perhaps our natives are more invasive. In the chaparral climates, there is not much area for them to be invasive in. Yet, in riparian situation, they can really dominate.
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
I know fescues are looked to hear for certain kinds of “no-mow” lawns.
Loved seeing your summer garden! I’m all for using plants as weed suppressors! I tend to find that tall plants kill their smaller siblings though. I suppose it’s all about research and getting the right plants.xxx
On these sorts of questions, experience is the best teacher.
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.