Starting garden over sod

Question

We just moved into a new rental and have permission from our landlord to start a garden. Our yard has a great southern exposure, is very flat, and we're in Seattle.

I've never started a garden before and I'm getting pretty frustrated by all the roadblocks I'm hitting. :/

I was thinking this year I'd try not to bite off more than I can chew and to put in one 4x10 ft. raised bed. Maybe do another in the fall and have it ready for spring 2018. I have no particular aversion to another type of garden, but these seemed popular and pretty simple.

I'm getting a lot of conflicting opinions on this; do I need to remove the existing sod? I started to remove some and went through about a 3x3 area when I realized there was no way it was going to fit in our city compost bins. I'm not sure if I'm pulling up too much but the grass roots seem to be about 4" deep. If I have to I can rent a pickup and truck it to a yard waste disposal facility but I'd rather avoid that hassle if possible.

I've read about lasagna gardening, where you kill the grass with wet cardboard and pile things to compost on top. I wouldn't be able to plant until next year with this method and I was really hoping to have a garden this summer.

So I'm wondering... would I be able to put down wet cardboard over the desired area, build an 11" fence around it, and fill the resultant box with compost/topsoil? I only worry that when the plants get through that first 11" they'll hit the cardboard and the soil underneath will be so compacted they won't be able to grow into it. Could I lightly till the sod and then put cardboard on it?

I really don't need the world's best garden here, I'm just looking to get started without pulling out too much of my hair. Again if there is something totally different that I can try I'm totally open to it, seeing as I've done pretty minimal work so far.

Edit: Also I've been wondering about if it's reasonable to break up and aerate the sod, lay cardboard on top to ensure it's dead, and then add finished soil/compost on top. It's not a labor issue here I'm willing to work hard, I just don't want to spend days renting equipment and running all over town spending too much money.

Answer 1

Do not cut it out and send it off to the city for composting! You may get city compost back, but most of it won't be as good as what you are digging up.

You may have heard of "loam" - loam is nothing more or less than composted sod.

You want those nutrients right where they are. You might flip them if you are up for the labor, or just bury them if you have adequate compost available - either way they will compost in place quite nicely so long as they are buried adequately to keep light off them. You don't need cardboard or paper, but you can use those if you like.

If you won't have grass on your garden paths, cut those sods and add them to the beds.

If you are cutting and flipping the sods, you can loosen the soil below with a fork. I suggest doing that once, when you start the garden, and then just avoid walking on it. If it's more labor than you want to put in, feel free to move on to the "just don't walk on the beds" phase and let roots and worms take care of it.

Answer 2

There is another alternative - lift the sod in squares or oblongs, stack it somewhere, grass side down, preferably out of sight, and leave it to rot down. Over time it'll turn into really useful loam which can be reapplied to your beds.

Otherwise, I entirely agree with Ecnerwal's answer.

Answer 3

You're on the right track already. You only need to erect 6 inch high planks to mark out your raised bed, and then cover the sod with compost to that depth. Get a plank and place it over the compost and trample it down so it packs down. But don't walk on it just your shoes as that's too much compaction when there's not much organic material in the bed.

This forms a light blocking "mulch" which will kill the grass beneath. No cardboard is required, and in any case, people find thick layers of newspaper better as cardboard rapidly falls apart. You've mentioned that the grass roots are 4 inches deep. They'll all die under the light exclusion, and as they rot, they'll open up lots of spaces for the roots of your vegetables.

This is all best done in your growing season and you're ready to plant immediately, and the roots of the vegetables will have access to the nutrients released by the decomposing grasses.

Since this method is pretty low on labour, you might want to try one of the other methods as well and see which gives you the better result for the least effort.

Answer 4

It's quite important to know what kind of grass is in the sod you will be covering or composting. If you don't know exactly what the current mix is, dig up a few square inches of the sod to a depth of 4 inches or so with a trowel, then put a pint of water in a clean bucket/pail and wash off the roots. Now take the matted grass and tease it apart into individual plants making sure to keep roots attached to the respective plants, arrange them on a coloured background that best reveals the plants and roots and take a photo. Take the pail of dirty water, remove any remaining roots and leaves, swill it around vigorously and pour the whole lot into a glass quart jar and let it settle naturally in a quiet location. Several days later when it has clear water on top take a photo. You will then have two very valuable resources, an inventory of the existing grass types and a soil profile. These will be solid reference tools for you in future years as you gain experience, and two very useful photos to share with us as we try to help.