Six inch deep beds?

Hi all. I am new. Posted an intro under the welcome forum and asked a coupld of questions while I was there. I sure hope someone can answer them for me!

Another question. Do most of you stick to the 6' deep beds? I am not sure if I should do that or not. After spening all the $ for this new system, I sure want to do it right and get some good results.

Six inches are all you need for most crops except potatoes, long leeks, and long carrots. Since the roots are getting all the water and nutrients they need, they don't need to reach down and out so far. Really tall crops such as giant sunflowers or six-shooter corn may need some extra support when grown in shallow boxes, but most things do just fine.

We made some of our boxes 8" deep because that happened to be the size lumber we had. The MM usually settles a lot the first year, so you really end up using more like 4 or 5 inches in a 6-inch box, but it's still enough.

We built our first box 12" deep because I wanted to plant potatoes and long carrots. I made a newbie mistake and filled the entire box with MM. We could have used a cheaper filler material for the bottom 6" and then added the MM on top. We pulled that box up this spring to put hardware cloth on the bottom for vole deterrent, and this time we spread 6" of free-for-the-hauling rice hulls in the bottom, then added the MM on top.

Some people build all 6" boxes, and when they want to grow potatoes, long leeks, or carrots, they add a "top hat", or a 6" frame over a few squares, and then fill only those few square with extra MM. It's a trick that stretches the MM further.

Trust us. Six inches are enough.

You will find folks telling you that 4 inches is plenty for most things you will plant.

When you have perfectly conditioned soil, the roots need go no further. They just spread out.

Stay coachable to the system and you will be amazed at how easy things become. I urge you to ask ANY question before deviating from the system, like you did, and don't be afraid to ask for clarification, too. The SFG system was put in place to save work. And, making more than 6 inches of MM, without good reason (like for potatoes), is just adding both work and expense unnecessarily.

Keeping in topic, I bought 8in wood, easiest to get. I was just going to fill it all the way but after doing the math with someone's handy calculator I really am buying way more fill than I need. Does it make a difference if I do 6 in of MM but the box isn't full to the 8in top? Thanks :o)

Nah, you are fine. Welcome! By all means save the money on the MM. If you are planning on planting longish carrots, or parsnips, you might get away without a high-rise with a full 8-inch box, though. Sweet potatoes and spring (early) potatoes come to mind also. But for regular crops the basic 6" of MM is all you really need, unless you have extreme climactic reasons to use a deeper bed.

krazikandiland wrote:Keeping in topic, I bought 8in wood, easiest to get. I was just going to fill it all the way but after doing the math with someone's handy calculator I really am buying way more fill than I need. Does it make a difference if I do 6 in of MM but the box isn't full to the 8in top? Thanks :o)

Our 1' x 8' trellised beds are 8" deep. We didn't completely fill them last summer, and then with settling they wound up with probably 5-6 inches of MM. They grew great tomatoes and basil, though.

An alternative would be to put a layer of cheap filler in the bottom two inches of the box.

krazikandiland wrote:Keeping in topic, I bought 8in wood, easiest to get. I was just going to fill it all the way but after doing the math with someone's handy calculator I really am buying way more fill than I need. Does it make a difference if I do 6 in of MM but the box isn't full to the 8in top? Thanks :o)

I did the same. The 8" was cheaper than 6". So, I filled it to the top, loosely, and when it settled, I have around 5-6 inches. It leaves the perfect amount for mulch, too. And, since the peat and vermiculite won't ever decompose, I will likely fill it over time with my own composted materials.

Great post Ander!!

We have all different sizes and I like the 8" best for the 6” of mix I end up with in that box. My husband who sits on the wallet likes 12" but me who keeps the mix under my fingernails knows that 6 is enough (even when it compresses to 3 to 4" of mix)