Hello! As you can see on the picture I'm working on installing some new raised garden beds in an area that was previously only grass. We tore out the sod where they're going, and now I have to decide what to fill these with. I know a mixture of quality soil and compost is generally the idea. My big question is whether or not to put something else on the bottom under the soil. I know some people use cardboard or wood chips, but I'm not sure why, or if it's necessary when starting from bare ground. Any input welcome and thanks in advance!
by grumpy_penguin84
27 Comments
It is if you put it on grass and want to stop the grass growing though someone stated that they doubt grass would grow thru 12″ of soil. Since you’ve already got rid of the sod, I wouldn’t worry about it unless you have a bunch of boxes you want to get rid of. Put the soil down and 2″ to 4″ of compost on top. I usually say 4″ but that may be too much of an investment in this case. Wish they had these 40 years ago.
There’s no reason to put things in your raised bed besides a mix of topsoil and compost. If you put something like wood chips in the bottom of your bed your soil level will just drop faster over time, as those wood chips decompose, than it otherwise would.
You do want to mix the first bit of soil you put in there with the existing soil, so it’s not such an abrupt boundary between the two, to facilitate drainage.
I wouldn’t be super worried about weeds. Gophers and voles could warrant some hardware cloth being put down though
I throw straw in the bottom, and add cheap compost from the local dump for the first 2/3, then mix compost, vermiculite, perlite and coco coir for the top 1/3.
Started out buying bags of top soil and after 10 bags and it being nowhere near full, I switched
You can also put down ground cloth (I put down hardware cloth for gophers) if you’re concerned about grass… but it won’t grow through all that soil
You should look at why people say putting old logs and leaves and stuff in the bottom is good. It’ll feed your plants for years it you do it right. You can take that old grass and turn it upside down and put it in the bottom, too. Hugelkulture for raised beds. Filling in your box also saves on soil costs, which seems obvious but when you go to pay for it and move it, it does make a difference. They hold a lot.
How deep are those beds?
I did hardware cloth on the bottom to keep the dang voles and gophers out. Little tirds taught me a lesson on my first few raised beds.
Definitely recommend hardware cloth to prevent any gophers or other critters getting in! Beyond that, read up on hugelkultur. Old wood logs, plant debris etc. For me a big plus was needing less soil to fill the beds!
Hugelkulture. Cardboard layer, then lots of logs, sticks, leaves. These will break down slowly over time, and are free instead of paying for all the soil. Top 4-10 inches should be compost / soil.
Lay down cardboard at the bottom. It will help kill the grass seed and then later it’ll compost itself into the dirt below.
I just filled several beds and I found lots of leaves and sticks and dead grasses along the base of shady tree areas. Enough to fill several buckets. Your beds are deep enough that logs make sense but then sticks and grass. Leave your best soil for the top 3 inches
Bales of straw. Cheap, fills a ton of space, and breaks down into organic material quickly.
I used wood and branches from a tree we cut down years ago and palm tree trimmings and it’s worked perfect
1/4″ hardware cloth will discourage burrowing critters from getting up into your beds. Even if you don’t think you have them, it’s good insurance.
Here’s a take on filling a raised bed from someone who seems to research things.
https://youtu.be/c-BRQwfVn8Y?si=mvsFmqn8OE1V9Qr6
https://youtu.be/sLOiCiJIO6o?si=o4rFE76XHO4Xd5Cy
From what I’m led to believe it’s not just the first or second year of the soil condition but the long term growing medium you’ll end up with after it decomposes. Easy to create a bog.
I gather the leaves I was too lazy to rake up last fall and throw them in the bottom. They make great compost. If you have grass clippings, throw those in, too.
Do you have gophers
I did cardboard. In the same type of bed you have.
Worked great. I didn’t over think it though.
I would bet that you would get the same result without cardboard too. I don’t think it’s really doing much, but it was more peace of mind for me (I’m stopping the weeds and grass). Don’t put anything not organic though, like fabric or plastic etc. some people put logs, don’t do that either, here’s my opinion on that, breaking down wood robs soil of Nitrogens from what I’ve read, also wood doesn’t break down that quick, you’d likely need a season at min and two or three ideally before it’s adding anything to the soil. I would stick with cardboard or leaves, compost etc. have fun, don’t over think it.
I used sod for the bottom. You have plenty of room for lighter fill above it.
Where did you get the larger bed ? When buying mine it was a ridiculous amount for anything over 2 ft wide
I suggest hardware cloth and cardboard. On top you may add branches, leaves, kitchen scraps to create bulk. Just remembered kugelkukture is a thing where you put logs and they decompose. Especially good if your raised beds are over 12”.
Where did you get the beds? These are pretty nice but everything I’ve been looking at online seems way overpriced.
Definitely want logs on the bottom.
I put a layer each of cardboard, weed cloth and hardware cloth. Otherwise, gophers and voles wreak havoc, and rhizomatic weeds find their way in. The cardboard just keeps the other stuff under a layer of organic ‘mulch’.
I would put too much wood chip or logs in beds that deep. It’s easy to overdo it and that can lock up all the nitrogen in your soil. I definitely did that once. I’d look into getting a soil delivery. A dump truck with 3 yards of dirty might only be 200 bucks depending where you live. Can never have too much soil IMO!
Hardware cloth, cardboard, big logs, branches, leaves/grass, then work in your soil and compost. Saves money and enriches the bed!
We got these very raised beds and for the life of me wondering why I didn’t put the cardboard box packaging they came in at the base of the beds!
As I’m certain you’ve already discovered, filling these takes *alot* of dirt. The logs not only add nutrients, but take up space. Only the top 6”-1’ really need to be growing soil. I live in a sandy area, and filled the bottom 1/3 with sand, then logs, then sticks, bark, bush trimmings, etc. Then, since that took me about six months and planting season was over, I just threw all my compost and grass clippings in there and every time I added more stuff, I raked it out to turn the pile. When spring came, I filled the last 1/4 of the bed with manure and topsoil and tossed some perlite in as well to hold the moisture. On my second bed, I did the same thing, but bought bricks of coconut coir, which, on Amazon is pretty cheap (approx $10, 10 lb brick, when wet = 15 gallons). So far it’s worked really well in zone 7b
https://preview.redd.it/3nliz6c4riue1.jpeg?width=3407&format=pjpg&auto=webp&s=53b10ffb4058d0ae9dff0cb60fcb780c8fd2359b
I used some chicken wire, with some cardboard followed by some split logs and some branches i had from the yard and then filled with my raised bed mix. Bed height is 17″ and i aimed for a 10″ height of logs/branches leaving just 7″ depth needed for actual soil mix. I will top off each bed with some fresh compost each fall that I make throughout the year.