JTanguy
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Location: Mill Creek, Washington

What soil to use in a raised bed 15" deep for tomatoes?

Would a combination of bags of Miracle-gro potting mix and garden soil work. I don't care about the cost.

tomc
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Why a 15 inch tall raised bed?

No matter what you use to fill this bed you are going to have four or more weeks of settling out before planting. I think you are a dollar and a day late. For this year.

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applestar
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I kind of disagree about waiting four weeks -- I'm too impatient for that, and if you are not worried about growing the best looking most productive tomatoes in the neighborhood, you will have results, though I agree it might not be the absolute best they could be.

Is the raised bed open bottom to the ground below? My raised beds are all open bottom, so I always start out by making holes in the ground with the garden fork -- stand on it, then tilt to fracture the soil. I put the pieces of sod from the edge of the garden bed on top of the grass. Then my garden always needs some lime so I add dolomitic lime and sand, half finished compost, mushroom compost, used coffee grounds, weeds and grass clippings with possible seeds, cover with several layers of packing paper or a flattened cardboard boxes, water in well, then organic fertilizer and topsoil, finished compost and/or mushroom compost or a product called BumperCrop, coir, more sand. I think that's the rough picture.

I make an extra deep hole through the paper if necessary to plant the tomato plants deep, fill the pocket in the mulch with the good soil mixture so there is at least 2" or so good soil all around the root ball.

I don't have a specific formula or recipe, but generally above process works well, the soil will improve to at least the depth of the garden fork by next year, and it doesn't cost as much as taking everything out and filling with only good soil. But if you want to and can, then Yes, you could definitely fill the entire bed with bagged top or garden soil, good compost, and sand in equal mixture. If your bagged soil or compost is particularly sandy (this is regional, based on source I think) then you can reduce or skip the amount of sand.

JTanguy
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Location: Mill Creek, Washington

applestar, Thank you for the info. My bed is on a rock layered ground next to the house and cement parking pad (gets lots of warm sun) and is open at the bottom. I use galvanized fencing material on the bottom to keep critters out. I use 2x4 uprights with 2x2 cross pieces to form 4 separate "cages" to help keep the tomatoes supported. I also use automatic drip watering to minimize effort. All soil and/or amendments will be bagged type and purchased at either Lowes or Home Depot.

imafan26
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Check out your local green waste facility if you have one in your neighborhood. They sell compost by the truckload which is a lot cheaper than by the bag but some of them also sell soil mixes for raised beds also by the truckload a lot cheaper. All you have to provide is the truck. You can rent a truck, but even if you have one. Line the bed with a tarp and thick plastic sheet over it to make cleaning the truck easier. And don't forget the tarp and rope to cover the load. The garden mix usually is ready to fill and plant and may have had composted manure added or you can add fertilizer if it doesn't have any. Although I would probably water it well for a couple of weeks to make sure it is thoroughly moistened and draining well and give it time to settle before planting.

Is this place near you?
https://pacifictopsoils.com/products_all.htm

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rainbowgardener
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I have 16" raised beds sitting on a concrete patio. They are fine for growing tomatoes (except that over the years as the trees got bigger, the patio has gotten too shady for them, but that's not the fault of the beds). When I first built and filled them, I had a cubic yard of topsoil delivered (to fill two 8x4' beds). Way cheaper than bagged stuff (though I guess you don't care) and then I just heavily amended it with compost, a little bagged potting soil, and other organics.

Your soil will settle, but tomatoes respond well to having their stems buried (they can root all along the buried stem), so you can just add more soil mix later.



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