Raised garden beds

http://www.hometalk.com/search/posts?filter=raised%20garden%20beds

Most of the raised beds are 6" to 18 " deep depending on what you want to grow; root veggies need the 18" depth.

I don't know how much room you have on your deck... so I am going to give you some suggestions, that may give you and idea of what type of raised bed you are looking for, so you will know what you want to buy or have built. Cedar is a good wood for food crops, pressure treated wood is not (it is impregnated with a poison that kills termites and other pests that like to dine on wood.. it will leech into the soil, rail road ties are the same) Gardeners Supply Company has all sorts of raised planters (www.Gardeners.com) in a rather large range of heights, styles and sizes....

I, personally, like to use the galvanized horse water troughs (aka stock tank) they come 12 inches deep or 24 inches deep, are usually 24 inches wide, come in 3 ft, 4 ft , 6 ft, 8 ft lengths. Our Lowe's carries the 24X24X48 size in the garden department for about $90.. Any Farm and Garden supply (like Tractor Supply, etc. ) will have them for a similar price and they may carry a variety of sizes. Last year, I planted tomatoes, artichokes, carrots, peppers, green beans, radishes and cucumbers in mine. We have also had 3 small olive trees in stock tanks for 3 years (they will go in the ground this winter)

tomatoes do better with min of 12 inches deep for the roots. 5 gal buckets work nicely.

We have bought these planters from Home Depot and very easy to use. I was able to grow tomatoes, herbs and flowers. I have had these for 5 yrs and bought new ones last year.

https://www.homedepot.com/p/CITY-PICKERS-24-5-in-x-20-5-in-Patio-Raised-Garden-Bed-Grow-Box-Kit-with-Watering-System-and-Casters-in-Sandstone-2342-1HD/206936546

I would go as the eighteen inches so that roots have plenty of room to grow and get sturdy plants. I have pots that deep that I grow tomatoes, peppers and lettuce in and they do great. My tomato plant was five feet tall from the soil to the top and had six stakes that I had to use because they were so heavy with fruit. I kept my lettuce plants in the shade, out of the hot day sun and they were four feet high before they bolted. They did just as good as what I had planted in my veggie garden up in the back yard.