So, I'm building some garden boxes this year. We're building them out of 4 x 6's and will make them at least two high (1 foot) if not 3 high. It's a little easier on the back!

Anyway, I'll line the boxes with some sort of plastic. I'm curious about the soil though. How should I go about filling them. I certainly don't want to fill them with dirt from my yard. It's hard as a rock and very acidic. Should I buy soil from a local place and till peat moss into it? How should I go about this?

First, if you are lining these boxes with plastic, don’t forget to have some drain holes so you don’t drown the plants. Put large gravel on the bottom to help drainage and to keep soil from washing out through the drain holes.

What I used for Mrs. WoW Garden boxes I made for her out of redwood was bagged top soil I got from Home Depot. You can pick it up at any DIY or garden store.

2 parts top soil with one part composted material.

OR 1 and 1/2 parts top soil, 1/2 part sand and one part composted material.

OR 2 parts top soil, one part sand, 1 part composted material and 1 part mulch material along the lines of fine to medium shredded bark.

The first part is good for plants that produce a fruit, tomato, squash, and bell pepper.

The later is good for root crops like potatoes, turnip, and onion.

The last is great for plants like corn, soy beans, and other high nutritive needful plants. Or plants like Rhubarb, Asparagus which will be in the same plot living several years in a row thus you will not be able to add more compost without disturbing the plants.

Why I keep throwing sand in there is because sand promotes drainage. There is a tendency for box plantings with regular top soil to clump into a tight package at the bottom under its own weight, this catches water and leads to root rot. Sand will prevent a lot of soil compression and will even under conditions of compression still allow water to drain.

Of course you will not have to fill a full 3 feet of good soil into a 3 foot box. Unless you are planting deep root crops or a bush or a tree. If you are sticking with regular vegetables and perennials and annuals you only need 6 to 8 inches of good top soil mixed with compost.

Potatoes, turnips, carrots, and other root crops may need about 1 foot. The rest pretty much stick to the top of the earth root wise and do not more.

So you might want to use general fill to make up the difference.

Okay, I think that helps out a lot. I was curious about how deep to make them. It sounds like I'll be okay with only making them a foot deep? I'll be planting mainly tomatoes, peppers, scallions...no deep root veggies.

Thanks for all the help everyone!