Best Soil For Raised Bed Vegetable Garden

[Karl Helser]

Just put in a 8' x 4' raised garden bed. I'll need about 2 cubic yards of soil. We'll be planting such things as peas, spinach, tomatoes, lettuce...etc.
What would be a good soil mixture. We plan to buy bags, but are unsure of the ratio of the mixture.

[CharlieBear]

Here is some of what you are up against---
Potting soil is not soil but a soilless mixture usually containing wood product remains, perlite or equivalent, possibly sand, fertilizer etc. It is best used for large pots that have to be moved in and out during the year.
"top soil" in most states can be anything and generally isn't very good stuff. It often is full of weed seeds and can be subsoil in most states. In a few states it is little more than soilless mix. Even if you go to a yard and buy 1 or 2 yards at a time it can be little more than clay or can even be mildly contaminated.
One solution that works is to go to one of those places like a fuel company that sells bark mulch and buy mushroom compost. It will sink down and you will have to add compost etc year after year to bring the level up and the nutrients back or even a little composted cow manure. The one draw back to mushroom compost is that it has a slight salt component.
So, if you are concerned about that you could mix 1/2 mushroom compost with "top soil" or even potting soil.
If you buy anything in bags the cost will eat you up alive quickly. I just noticed where you are from. Go to Mt Scott Fuel and get mushroom compost. One cubic yard will fill a standard size pickup truck bed, so if you don't have access to one I would ask around to see who has one they will let you use or drive it there and back for you. Note in the portland metro you will likely get clay and very weedy clay if you buy top soil, as many of my gardening friends have found out. If you want to ask more questions send me a personal I usually forget to check back on questions I have answered. There are other possiblilities of course, but space is limited.

[rainbowgardener]

Two cubic yards sound excessive for one bed, even if it is deep. I have beds that are 18" deep, 8' x 4' and if I remember right, it took one cubic yard to fill it. But if you are dealing in cubic yard quantities, it is way cheaper to get it trucked in. Get someone to deliver you a cubic yard of topsoil and then fil in the rest with bags of potting soil, compost, composted manure.

[cynthia_h]

Hypothetical math calculations:

8' x 4' x 1' deep = 32 cubic feet = 1 cubic yard + 5 cubic feet left over

8' x 4' x 18" deep = 48 cubic feet = 1 cubic yard + 21 cubic feet left over

8' x 4' x 20" deep = 53.3 cubic feet = 2 cubic yards, almost exactly (2 CY = 54 cubic feet)

8' x 4' x 2' deep = 64 cubic feet = 2 cubic yards + 10 cubic feet

So it looks like these may be 20" deep, or the OP simply wants to make his life easier by rounding off to the nearest cubic yard.

Cynthia H.
Sunset Zone 17, USDA Zone 9

[Karl Helser]

Thanks Cynthia, you are correct. My bed is 20" deep....I already did the math, and that's how I came up with two yards.

FYI... 1 cubic yard = 27 cubic feet
1 cubic foot = 1728 cubic inches
With those factors and the dimensions of the bed, it's real easy to calculate how many cubic yards needed.

Thanks rainbowgardener and CharlieBear, you were very helpful with your information. I am definitly going to use a large pick-up truck instead of bags.
I found a landscape supplier that has what he calls his Blended Premium Soil. It's a mixture of sandy loam, mushroom compost, and premium compost. Sounds like just what the vegis ordered

[cynthia_h]

Be sure that the Premium Soil is designed for "containers." It may be designed for in-ground use.

Raised beds are a kind of large container, and need larger pore spaces in the soil than the native ground does. This is why many potting mixes (and even Mel Bartholomew's recommended soil blend for Square Foot Gardening) include perlite, vermiculite, or other "air-friendly" (?) ingredients.

Cynthia

[DiJon]

I've talked to many raised bed gardeners in Portland. the native soil is so clay filled, and it rains so much here, that you really don't want too much of it in you beds, or you will be battling damping off all spring. You can get a potting soil mix called 5f and mix that with some manure compost, worm castings and a cup or two of feather meal and bone meal add the compost, feather and bone meal every year.

[Gary350]

I buy Peat Moss in the 3.8 cu ft bales at Lowe's when it is on sale. I dump in on top of the soil 6" deep then I till it into the soil. Then I put it in the raised beds it is 50/50 peat moss and soil. It works great and does not cost much.

[floridahillnursery]

Hello, Mushroom compost and peat moss blend. If there is a mushroom factory in your area they unload the compost by the tonn and its very cheap.

[LA47]

We are putting in raised veggie beds next year. Getting decent topsoil is out of the question in our area. I planned mixing one third compost and well aged manure with the soil. I'm very nervous about using peatmoss as it seems to repel water yet that is what SFG recommends as 1/3 of the mix. What keeps the peatmoss from repelling the water in the raised bed?

[applestar]

I think if you add 1/3 compost, you wouldn't need peat moss.

I never buy peat moss any more. Most bagged potting soil are still made with them, so I end up with them in the compost pile and raised bed eventually, but I usually only use turned over sod (from other areas -- I only fork the ground where raised bed is to go), good soil from other areas of my poperty (usualy under the leafpile or stickpile), compost, fall leaves, grass clippings and cut weeds, sand, composted mulch, cardboard for weed suppression, small sticks and branches.

Not in that order but layered as sheet mulch/compost. Dolomitic lime, rock phosphate, and greensand. Sometimes used coffee grounds and soaked alfalfa pellets.

[Gary350]

In my TN garden I used peat moss only. I would buy several of the 3.8 cu ft bails every year and till them in to the garden soil. The Pepper Plants especially loved it for some reason pepper plants would get 6 tall, bell peppers were 5" diameter, sweet banana peppers were the size of real bananas. Tomatoes, squash and beans liked it too. Corn and okra did not seem to care.

I would dump peat moss 4" deep 20" wide the width of the tiller in the row I want it, then till it in. It was like a raised bed without building a raised bed with boards. It only took 10 minutes to dump peat and till. About 50% of the peat had to be replaced ever year it composts away pretty quick. One bale of peat moss per row would tripple my pepper harvest. All the greens loved it too.

I made 3 lbs of red chili powder one year ground up dried chilis in the kitchen blender.

I could never make enough compost to do what I needed, peat moss was the cheapest alternative.

[imafan26]

Peat moss I think has a pH around 5.5. It provides good root support and peppers and most plants like a slightly acidic soil. It does not provide much in the way of nutrients so I suspect you also fed them very well.

Peat moss is a natural product but it is being mined faster than it is being made. I'd use more of it in my garden, but I can't afford it. So, instead I use compost and I will dump out the peat lite from my potted plants into the garden as well so it does get a little bit of peat moss.

[jon052101]

hi, if i mix .75 cu ft of composted manure and .75 cu ft of topsoil, is it the same as 50/50? thanks

[ElizabethB]

My 2 cents

Option 1 - purchase bulk soil
advantage - less expensive
disadvantage - weeds and soil quality - have to do a soil test

Option 2 - bagged soil
Advantage - easy to handle
disadvantage - expensive

Option 3 - 1/3 compost, 1/3 course horticultural vemiculite, 1/3 peat moss.
Advantage - virtually weed free except for weed seeds that birds drop, no more expensive than bulk soil if you shop around for your products and have your own compost
disadvantage - you have to mix it

SOOO lots of options.

Good luck

[imafan26]

jon, manures are added to the garden bed to provide nutrients. Because fresh manures can contain weed seeds and pathogens, it is safer to add the manure to the compost pile instead or to add manures in the fall (where there is snow) so it will have plenty of time to mature before spring planting.

Manures vary in their NPK value and in general most of the numbers will be under 5. Not all of the nitrogen is available immediately as it has to be mineralized by soil bacteria before it can be taken up by the plants. Manures can also be very high in salt. Rain and maturation of the composted manure lessens the impact of the salt. However, composted manure may actually be very high in salts because most of the moisture has been lost in the composting process, thereby concentrating the salts.

If you are using composted manure on the garden you should only spread about an inch over the garden area and work it into the top 6-8 inches. It should be applied ideally in the fall or at least 6-8 wks before planting. (90 days before the first harvest).

https://www.cmg.colostate.edu/gardennotes/242.html

On an established garden, the best thing to do is to add 2-3 inches of good quality compost every year and follow soil test recommendations for fertilizer and pH management.

[ExcitableGardener]

Personally I've had a lot of success using the 1/3 peat moss, 1/3 soil, and 1/3 compost mixture. That being said, when I first started gardening I filled my first bed with plain old topsoil and some miracle grow and still ended up with a nice harvest.

If you don't mind the extra cost, it can't hurt to go with the first option. Otherwise, just get some dirt and some compost and you should do fine.

[gillespieza]

I've found peat moss to be very expensive (at least here in South Africa), so I use coir peat instead. It's about 20% of the price, and I've had great success using a 1:1:1 mix of compost, vermiculite and coir peat.

[SouthernStyle]

I use half top soil and half composted chicken maure from our chickens. The maure is just wood shavings that we put down and when it needs cleaning out we put it on the compost pile and let it cook for up to 6 months before using. I never use any chemical ferts and the soil in my beds is good for anything you want to grow with no feeding.

-SS-

[Wabernathy]

I work from raised beds as well, and 2cu sounds about right (i don't have my journal handy to confirm) but in a 4x4 raised bed, and I use 2x8s filled to six inches, that means there is 2 cubic feet of planting (4 sq feet/2). Yes, that's right;)

My soil planting mixture is the old Mel's Mix from the square foot gardener series on PBS:

1/3 peat moss
1/3 vermiculite
1/3 compost mix, and that mixture contains at least 3 different types, in equal proportions.

Here in NH, the simplest to pick up are seaweed, cow manure, and blueberry. My own compost bin is for enrichment, not initial bed 'seeding'.

This mix is self sustaining in its design, as the peat moss helps retain moisture, the vermiculite aids in draining excess water (never over water again:), and the mix of compost makes sure I don't have too much of one nutrient, and not enough of another.

I have grown a variety of crops in this mix, starting with lettuces, beans and peas in the early season with great results, followed by summer crops like toms and peppers, corn and the like (yes, you can grow corn in raised beds), and squashes in the late season. All came out amazing...

Yes, these are my budding lettuces in the mix.

[ElizabethB]

Karl just curious - have you filled your beds yet? If you have not - a suggestion - in raised beds you can grow just about any garden vegetable except potatoes in 8" of soil. 20" really is more than your need. A raised bed is one of the few times I recommend a weed barrier underlayment. If you opt for fabric buy woven, commercial grade. You can also put down a couple of layers of heavy cardboard from appliance boxes.

Check out https://www.squarefootgardening.com

I am a big fan of this space saving, intensive gardening method. Lots of produce from very little space and easy maintenance.

Good luck

Keep us posted on your progress.

[rainbowgardener]

Karl's post on previous page was from 2012....

8" is deep enough if you have half way decent soil under it. If you have pure clay or rock or like me, concrete patio, I would go with the 20". Especially if you are only doing 8", I wouldn't want the weed block, just cardboard, which will get itself out of the way, so that your plants can root down into the soil below.

For wabernathy - on page 1 of this there are e.g.s of the math

"but in a 4x4 raised bed, and I use 2x8s filled to six inches, that means there is 2 cubic feet of planting (4 sq feet/2). Yes, that's right;)"

4x4 (=16) x 1/2 = 8 cubic feet. 27 cu feet (3 x 3 x3) make a cubic yard, so 8 cubic feet = .29 of a cubic yard.

you are only off by a factor of nearly ten....

[Voices30]

I use `1/4 top soil 1/4 comost 1/4 peat moss and 1/4 sand. But this is very specific to my growing needs and the existing soil where I am growing. I live in North Central Florida and it's similar to Georgia. Remember that even though you are planting in raised beds, consider what is directly underneath it, depending on what you are growing the root structures may pass down into the ground beneath the bed. For example watermelon can grow roots up to 4 feet deep depending on the variety.

[feldon30]

It's kind of a myth that only root crops need more than 8-10" of soil. All crops will benefit from extra room for roots. This is as per Ed Smith's the Vegetable Gardener's Bible.

Also, I tried weed blocker my first year. What a disaster. I exhumed all the soil and removed the weed blocker and found I didn't need it, and after several years, I had dramatically improved the gumbo clay underneath.

[steve104c]

Best garden mix is 1/3 compost,1/3 peat moss and 1/3 vermiculite. Water retention is great. Drains well,moist but not wet for 3 days between watering. I have 55gal. plastic drums cut in half on stands. No bending to weed, plant, water and harvest.

[lexusnexus]

Also, I tried weed blocker my first year. What a disaster. I exhumed all the soil and removed the weed blocker and found I didn't need it, and after several years, I had dramatically improved the gumbo clay underneath.

Although I've never done raised beds this makes the most sense. If you put plastic under your raised bed aren't you essentially doing container gardening writ large? I'd think you would want to have the benefit of natural soil (well, amended natural soil) as part of your garden.

[feldon30]

Also, I tried weed blocker my first year. What a disaster. I exhumed all the soil and removed the weed blocker and found I didn't need it, and after several years, I had dramatically improved the gumbo clay underneath.

Although I've never done raised beds this makes the most sense. If you put plastic under your raised bed aren't you essentially doing container gardening writ large? I'd think you would want to have the benefit of natural soil (well, amended natural soil) as part of your garden.

Exactly!

[Cola82]

I also had the same thoughts about laying down a weed barrier. I laid down plastic to kill the weeds for a while and then hand tilled the ground under my raised bed, ripping up as much of the clover root system as I could. Then I tamped it down a bit and put newspapers down, and put the compost over the top of that, then the bagged soil, then a little more compost and mixed it up a bit.

I don't know that this is in any way ideal, but I read that as the newspaper breaks down, the plants above will send their roots down through it. It seems like more of a psychological barrier than anything, which I'm okay with.

[nevadadeb]

Hi, I am new to this group as of today. This year I am attempting my first raised bed gardens and will be growing vegetables such as tomatoes, bell peppers, spinach, arugula, leeks, carrots, beets and fennel. A big list for a first timer. So far I have 3 beds that are 4' x 8', I am filling one today with the following:I have a weed barrier at the bottom (geocloth) then 3 inches of "western bark" (Ace Hardware brand), then 3.6 cf of peat moss (maybe 4 inches deep) followed by a 4 to 1 mix of Miracle Grow Garden Soil with one bag of Steer Manure/compost. The bed is about 1/2 full and wonder what you would suggest I add more of or perhaps something else. Any advise is gratefully appreciated, I would not like to lose all of the plants I have been starting inside since March.
Cheers,
Debbie

[rainbowgardener]

Hi, I am new to this group as of today. This year I am attempting my first raised bed gardens and will be growing vegetables such as tomatoes, bell peppers, spinach, arugula, leeks, carrots, beets and fennel. A big list for a first timer. So far I have 3 beds that are 4' x 8', I am filling one today with the following:I have a weed barrier at the bottom (geocloth) then 3 inches of "western bark" (Ace Hardware brand), then 3.6 cf of peat moss (maybe 4 inches deep) followed by a 4 to 1 mix of Miracle Grow Garden Soil with one bag of Steer Manure/compost. The bed is about 1/2 full and wonder what you would suggest I add more of or perhaps something else. Any advise is gratefully appreciated, I would not like to lose all of the plants I have been starting inside since March.
Cheers,
Debbie

I'm sorry. I wish you had written in BEFORE you laid all that stuff down. I think most of it is a mistake. If you read any of the rest of this thread, you do not want weed barrier at the bottom. You want your plants to be able to root down in to the native soil. You said 4x8, but you didn't say how deep. If it is at least 16" deep, then maybe the weed barrier doesn't matter too much. Less than that it will be a problem. Then why did you put the bark in? Bark is mulch, it goes on top of the soil. If in is in the soil, it will rob nitrogen from the soil in the process of breaking down. You were maybe thinking you were making a drainage layer, like people used to put gravel in the bottom of flower pots? But that was a mistake when they did it too. If you have a layer of soil and then a layer of gravel in a flower pot, water won't cross the boundary between them and you get soggy soil with dry gravel under it. But in your case if wouldn't matter anyway because then you put all that peat on top of it, so no water was ever going to get to the bark. Peat is a soil amendment. If is NEVER used by itself. If it dries out it repels water. If it eventually gets wet, then it sucks water up. Neither is what you want for something sitting under your soil. The peat should have been mixed up with the soil and composted manure, no more than 1/3 peat in the mix. Then what you want to add to the mix with your soil, manure, and peat is a mineral element to keep your mix loose and free draining and keep it from compacting. That could be perlite, vermiculite, crushed granite, coarse sand, etc.

Honestly, I think it would be worth it to dig everything up and start over. I think you will be very disappointed in your results otherwise. Dig everything out so you have an empty bed sitting on top of soil, no weed barrier. Loosen up the top layer of soil a bit with a garden fork and poke some holes down in to it for drainage. Then fill the bed with your mix of soil, manure, peat, and perlite or whatever - all mixed together, NO LAYERS.

Most of what you planned to plant should be OK, but spinach is a cool weather crop. If it is already warm (days regularly in the 80's and warm nights), spinach is over. It can be planted at the end of summer for a fall crop.

[nevadadeb]

Thanks so much for the advice ... There is about 6 inches of gravel that the beds sit on. The bark was a suggestion of a local gardener..bad advice. The temperatures are still below freezing at night. So if I mix in more soil with th peat moss and manur...does it have a chance? So sad.
Deb

[nevadadeb]

I did forget to mention that idid work the soil, peat and manure together well and the bed is 12 in deep.

[rainbowgardener]

I did forget to mention that idid work the soil, peat and manure together well and the bed is 12 in deep.

yes you did forget to mention that. When I read "I have a weed barrier at the bottom (geocloth) then 3 inches of "western bark", then 3.6 cf of peat moss (maybe 4 inches deep) followed by a 4 to 1 mix of Miracle Grow Garden Soil and Steer Manure/compost." I had the distinct impression of layers, including a 4 inch deep layer of pure peat moss. That is what I was reacting to.

[JPNguyen]

A lot of great advice and suggestions here. I never really thought much of my soil besides using just the basic miracle grow.

[Fishman2014]

I figured it was best to ask here than make a new thread. Anyway, I've been reading tons and researching for maybe too long, now I'm overloaded on info and just as stuck as I was when i started.

I'm making a little raised bed 4'x5'x15" and I just can't decide what to fill it with. Buying soil in bulk from a local nursery isn't an option, so it looks like I need to buy bags from my local hardware store. Buying it all bagged isn't going to be too cheap, and I have a few questions and ideas....

Can I use some of my not so good native soil from another area of the yard, mix some Peat Moss and perhaps a little Perlite in it to make some decent "filler" soil? Then I would buy some potting/raised bed/bagged soil and mix it all together to fill my bed. After all that, I was thinking of maybe getting a bag of THIS (it's much cheaper in the store) and mixing that in too.

Any ideas or suggestions would be greatly appreciated.

[rainbowgardener]

Buying in bags from the hardware store will not be cheap. If you are going to put topsoil in, have you looked in to having a cubic yard of topsoil delivered by truck? That's what I did. A cubic yard may be a bit more than you need to still have room for other additions, but you probably have other places in your yard that could use a little fill.

Whether your native soil or imported topsoil, it shouldn't be more than about 1/3 of your bed. The rest would be peat moss or coconut coir, compost (preferably various composts from different sources), and some lighter material that isn't going to break down too fast, too keep your soil loosened up, like perlite, vermiculite, rice hulls, crushed granite, etc.

[Fishman2014]

Out where I live, it's going to cost more to get it delivered than buying the bags. I might get a little more soil getting it delivered but my main goal is to just get what I need for this bed...for as cheap as I can. Oh, and of course try to do it best I can so the plants are happy.

So I can use native or top soil, but just don't let it exceed a third of the bed. I'm going to need about 22 cubic feet. How does this look?

- 6 ft³ native soil or bagged topsoil
- 3 ft³ peat moss
- 3 ft³ compost/manure mix (1/3 ecoscraps, 1/3 steer manure, and 1/3 chicken manure?)
- 10 ft³ of bagged potting soil/raised bed soil

[imafan26]

I remember the old garden books recommending 20% topsoil, 50% coarse sand, and 30% organic matter (compost or peat moss). Does anyone recommend that anymore?

Clay soil has its issues but it can still be the basis of a very productive garden.

When I moved in to this house, there was already a raised bed, it had not been cared for in years. It contained mostly red clay soil and I turned that into my vegetable garden. It was productive but because of the clay soil, it could be rock hard when dry and impossible to work wet. Not to mention that when clay is worked wet the soil texture is ruined and it forms clods instead.

Over time, I have added a lot of organic matter, made more than a few mistakes, but the garden is still productive. I did get a soil test and so I now pretty much only add nitrogen and compost because it is all that it needs.

Rather than try to fill the whole container bed with a homogeneous mix, why not do a lasagna garden instead.

To cut costs you could just build a lasagna bed (sheet mulching), especially if the container box is deep, it will help with the costs. That way you could build it in the fall and then let it settle in over the winter and be ready to plant in the Spring or if you do Fall planting, you only need about 4 inches of topsoil or compost for planting.

The ingredients for sheet mulching will probably be easier to find, newspaper, cardboard, kitchen waste, brown leaves, straw are not that hard to come by. You can ask your neighbors for leaves and kitchen scraps, and if you go to some restaurants you can get the coffee grounds, even coffee filters are fine, and if you are lucky contact the manager of the supermarkets, they will have produce that goes bad and needs to be tossed out so you may be able to get those items on their culling days.

[Fishman2014]

I got it all filled, and so far so good. Everything is happy and growing. Thanks!

[Fishman2014]

I got it all filled, and so far so good. Everything is happy and growing. Thanks!

Well, the good didn't last very long. Probably safe to say my first planter box, despite my best efforts was a failure. Not really even sure what happened, it all happened so fast. I put one plant in first to test everything out...it looked good the next morning so I put the rest in. Next day I see one plant has what I self diagnosed as Phytophtora/Root Rot, next day my other best plant is half wilted and dead, the other few plants that are left look okay...for now.

I still have plants in containers in my yard and they all look good. I'm thinking the crazy heat we've had here (soil down in the planter box gets real hot) and poor drainage is what caused this. I'm going to wait and see what happens with the other plants in the box, but I fear the box is compromised. Not really sure what to do with it. I read that pretty much all soil has Fungi/Bacteria, but it's dormant and won't be a problem until growing conditions are met. So maybe I can "fix" the bed still.

It sucks and leave me feeling defeated, but I guess you live and learn from mistakes. Next time I need to do something different.