Permanent ground covers for vegetable beds

Permanent ground covers for vegetable beds

We will be experimenting with permanent ground covers in our vegetable beds – specifically planting and allowing perennial plants interspersed with our vegetable crops. The purpose of this is to keep essentially a living mulch to help conserve water, suppress weeds, and to keep the ground covered with leaves engaging in photosynthesis. This will ensure that the life in the soil is being continually fed by root exudates.

I’ll be writing a post later about the biology of the soil that will give much more context to this. 🙂

One important note is that I’m not leaning on these crops to fix nitrogen, a role commonly given to cover crops, although they will certainly help to make nutrients available to the plant by maintaining a vibrant soil food web.

I want to see what it is like to disturb the soil as little as physically possible: sowing or transplanting into fully intact ground covers. No strip tilling, no mowing even. For this reason, they need to be short. I’d love to include dutch clover as a nitrogen fixer, but in most of the annual beds it simply grows too tall. Doing this with crops grown as annuals (like spinach, broccoli, or carrots) is pretty far out. I don’t know how well it will work – this is most definitely experimental.

I made a list of plants starting from Elaine Ingham’s list of perennial cover plants, then finding ones that seemed like they were a good fit for my climate and market farm context. I was looking for plants that:

  • Are tolerant of foot traffic. Although we intend to have permanent paths and beds, so plants that can’t take foot traffic will probably just not grow in the paths.
  • Are easy and inexpensive to establish but not too aggressive
  • Are pretty short, because I’ll be growing these among annuals
  • Are not woody, so that if I need to, I can cut or rake them away from the soil easily, and seeding / transplanting tools don’t get gummed up.
  • Tolerate wet / moist areas. We get a lot of winter rain, and I will likely be irrigating at least some in the summer – this needs to not kill the plants.
  • Tolerate dryness / drought. This is a little at odds with the previous point, but I’m looking for a mix of plants. We have dry summers, and I want to be able to get away with as little irrigation as I can to grow the crops.
  • Dense growth habit. I’m looking for plants that will grow densely and cover the soil to protect it from rain compaction, evaporation, and excessive weed seed germination.

My process was to scan through Elaine Ingham’s list, and then perform an internet search for any plants that were at most 2-3 inches in height or shorter. I confirmed their short height, then made a pretty quick snap judgement based on the criteria listed above. An images search that showed the plant growing around pavers or in a walkway was an almost sure sign that it fit the criteria I’m looking for. This was a quick-and-dirty process so I could get on with the rest of the planning for this growing season. Please leave a comment if you have any suggestions or critique!

Green carpet, aka Smooth rupturewort (Herniaria glabra)

This grows 2-3 inches tall, and sends down a deep taproot. Excellent! This means that it will not be competing for light with our crops, and hopefully largely keeping its roots deeper than the crop roots, while deeply feeding and loosening the soil. We will get seeds at $8.99 for 10,000 seeds here.

Pros: no spreading rhizomes, deep taproot, fairly soft and easy to manage

Cons: this may be too tall for the annual beds. We’ll see.

Lemon Frost Thyme (Thymus x citriodorus)

This grows 1/2 inch to 1 inch tall! And supposedly has a wonderful fragrance to it. I imagine this would be a bit trickier to get established – the tiny seeds would probably require growing as transplants to successfully establish a stand. Nevertheless, the very short height and attractiveness of the plant makes it worth trying.

Pros: extremely short, pleasant aroma

Cons: if it is anything like normal thyme, it might get a bit woody.

Dandelions (Taraxacum officinale)

This will definitely be experimental. Depending on circumstances, dandelions can grow quite tall (a foot or so in my area), or they can have a rosette that tightly hugs the ground. Joseph Lofthouse says that in his region in Utah, dandelions will grow short if it is dry and sunny, and tall if it is moist and shady. He intercrops it in beds with garlic.

Pros: a valuable rootcrop, leafcrop, and flowercrop, inexpensive and easy to obtain, deep taproot can deeply feed soil

Cons: might get to tall if conditions trigger height, might compete for water too much

Alpine strawberries (Fragaria vesca)

These are drought tolerant, nicely spreading… strawberries! The berries are tiny and inconvenient to harvest, but might make an occasional treat when working in the fields, especially for the kids. Suggested by John in the comments, and a few posters over at permies.com. I’m a little concerned that they may be too tall, but I’ll see.

Pros: easy to establish, drought tolerant, berries!

Cons: the runners might get annoying, it is taller and bushier than some of the other options here

Sedum requieni

This was added after Scott Dilatush mentioned it in the comments. I’ll quote what he said: “This drought tolerant evergreen plant grows only 1/4 inch tall and makes a dense mat that takes heavy foot traffic. Extremely easy to hoe. Soil prep is a must for longevity.”

Miscellaneous ground covers

These ground cover plants seem fairly similar so I’m lumping them together. They grow 1-2 inches tall or so, and readily spread to cover an area. Some of these like to stay moist, and others like to dry out between waterings. So we’ll see how they do!

  • Miniature Brass Buttons (Leptinella gruveri)
  • Alpine Brass Buttons (Leptinella minor)
  • Blue Star Creeper (Pratia pendunculata)
  • Scotch Moss (Sagina subulata ‘Aurea’)
  • Fine Tide Turf (Selleria microphylla)
  • Wooly Thyme (Thymus pseudolanuginosus)
  • Reiter Creeping Thyme (Thymus Reiter)
  • Wallowa Mountains Mossy Sandwort (Desert Moss)

The final mix

There were a few almost-duplicates in there – multiple Thyme species and a couple Brass Buttons. I’m trying to keep things simple for now, and don’t want a mix dominated by any one genus, so I removed “duplicates” and came up with this list:

  • Green carpet (Herniaria glabra)
  • Lemon Frost Thyme (Thymus x citriodorus)
  • Dandelion (Taraxacum officinale)
  • Alpine strawberry (Fragaria vesca)
  • Miniature Brass Buttons (Leptinella gruveri)
  • Blue Star Creeper (Pratia pendunculata)
  • Scotch Moss (Sagina subulata ‘Aurea’)
  • Fine Tide Turf (Selleria microphylla)
  • Reiter Creeping Thyme (Thymus Reiter)
  • Wallowa Mountains Mossy Sandwort (Desert Moss)

I’ll probably sow a bunch of seeds in pots, then pluck out individual seedlings to transplant into the beds on a 3 inch spacing. Some beds will get a mono-cover, and others will get mixes of the plants. I’ll only do this in some portions of some beds, so we’ll be able to compare the impact of the different plants, the mix, and bare soil or mulch.

18 thoughts on “Permanent ground covers for vegetable beds

    1. That stuff looks wonderful! It’s a bit taller than what I’m shooting for here, though. I’m wanting to start with super, super, super short stuff to give the highest likelihood that I can make this easy to manage in the market farm context.

      Next year when I have brainspace for more experiments I might throw some in a few beds and see how it does. You should try it this year and let us know how it works in your context. 🙂

  1. I’ve grown fond of Kenilworth ivy (not an actual ivy). It’s drought tolerant, spreads fairly quickly but is easy to remove and pretty.

    1. Ooh, thank you for sharing that, Maia! I just did some research, and based on that and what you said this seems like a very good candidate. I especially like that it can be content in full shade (the list was somewhat deficient in shade lovers) and does well in a mediterranean climate. I’ll add this to the list. 🙂

      1. Uh-oh, it looks like Kenilworth ivy can be invasive, and can climb on things. I’d be a little concerned about putting it in the mix after learning that, so I removed it from the list. Thanks for mentioning it, though, Maia!

  2. this is exciting!
    i want to keep up with your experiment..and maybe do a little of my own.

    in the middle of north carolina, we have hot summers and fairly mild winters. summers can be very wet or very dry or somewhere in between.
    we definitely seem to be gravitating to more extreme weather. average is 40 inches annually.

    do you have a sense for something you might try under those conditions?

    fwiw, here’s something i found on kenilworth ivy. the only reports of invasiveness are in the bay area…though i can’t tell if it’s significant

    http://www.invasiveplantatlas.org/subject.html?sub=14694

    1. You should definitely do some experimenting of your own, and let us know how it turns out! If you want to keep in touch you can email me at garden@jasonpadvorac.com any time.

      As long as you have mild winters, I imagine the things I listed here should work – at least, as a mix where some of them probably won’t work at all, and some might work. You might want to try strawberries, too, as recommended by John in another comment.

      If you want to put in an hour or two at the computer, you could go through Elaine Ingham’s list yourself, and research the plants to see if any of them fit your climate. She’s got a list on this page for a couple different regions – not the south, but some of the plants very likely would work for you: http://www.soilfoodweb.com/Cover_Plants.html

      Thank you for the note about it being invasive! I looked into it a bit more, and couldn’t find a clear answer as to where it is invasive, but it certainly is a problem somewhere. And in that searching, I found out that it can climb up things – uh oh. That is *not* what I’m looking for. It’s a bit sad, but I think it needs to come off the list. Thanks again for mentioning this!

    1. I did consider it, because it’s on Elaine Ingham’s list that I used as a starting point. It looks like a fantastic plant for this kind of use, but it grows about 6 inches tall, so it is taller than what I am looking at for now with my annual vegetables. In beds with perennials or other particularly robust plants it might be a good fit, or if you were going to use strip-tilling or mowing.

  3. amazing – this is exactly what I have been trying to do!( I am in portland oregon)- starting from Elaine’s list and then trying to figure out what to start with, and where to get seeds. I got stuck on where to get the seeds. I see that you listed one source for seeds – have you located sources for the rest yet?

    1. Wonderful! Keep me posted as you experiment, I would love to learn from whatever you try.

      I haven’t sourced the rest of the seeds yet – my plan is to do web searches for the varieties, then compare prices at the top few places that don’t seem sketchy and go from there.

  4. Sedum requieni
    This drought tolerant evergreen plant grows only 1/4 inch tall and makes a dense mat that takes heavy foot traffic. Extremely easy to hoe. Soil prep is a must for longevity. It will take watering if you have your paths raised. I’d try a small experimental bed (path) made of mostly scree (granite rock dust). This is like crush and run driveway mix on a miniature scale. It would be smart not to add anything to the soil mix that has weed seeds in it. A base of concrete sand underneath would provide much needed drainage. Grading needs to be done properly so there is no standing water.
    So many types of sedum. So little time.

  5. Great publication! Thanks, Jason! I’m looking to get permanent ground covering for over a thick layer of fallow wood chips, to build the soil under it and shade the chips in hopes they will decompose faster, adding more to the soil building. Will you have a layer of mulch, in which these will be? If so, what is the mulch material and how thick?

    1. I’m not sure yet – if add a layer of material on top it will be compost between 3 and 6 inches thick, but I haven’t decided if I will do that or not yet. If you had a thick layer of mulch, most of the crops I listed here would have trouble getting established. I think you’d want to pull the mulch back in places and plant these directly into the soil. Or you could use more vigorous, spreading groundcovers. And as the wood chips gradually broke down, you could switch over to the finer grained ground covers.

  6. you have inspired me to stop waiting, and try some permanent groundcover (I have been wanting to , but waiting until my list was perfect but of course it never was). I had a hard time finding seeds, so just got what I could from Outside Pride:
    Herniaria Glabra Seeds –
    Creeping Thyme Seeds –
    Strawberry Seeds –
    Irish Moss Seeds –
    Miniclover® Seeds –

    I plan to try in the winter squash, corn and yacon beds this year. I will let you know how it goes!

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