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.