I'll suggest a real favorite of mine, Angelonia. This heat and sun loving plant will bloom non stop, without any primping or prodding, up until the first serious frost. The purple one provides a color that really stands out in most gardens. Plant Angelonia (an jel O nia) at least twelve inches apart; they grow quickly to fill that space and more, and up to two feet tall. It's much loved by bees and butterflies, and even hummingbirds. No pest or disease problems that I've ever seen, but I don't have an irrigation system which can end up causing problems. Speaking of which, Angelonia is very drought tolerant once established.

Definitely and old thread but when in doubt for plant spacing I the "plant spacing: on the seed packet (or instructions). The row spacing is for :row gardening" where you need room to "walk or maneuver equipment" between plants for harvest or weeding chores. If you check the FAQs here... http://faq.gardenweb.com/discussions/2766684/what-are-recommended-plant-spacings Scroll down to... This is very helpful information from Mel's website on converting standard seed spacings to sqft spacing:"Depending on the mature size of the plant, grow 1, 4, 9, or 16 equally spaced plants per square foot. If the seed packet recommends plant spacing be 12 inches apart, plant one plant per square foot. If 6 inch spacing; 4 per square foot. If 4 inch spacing; 9 per square foot. If 3 inch spacing; 16 per square foot." I think the harvested size (and required spacing) will depend on the health of the soil. Keep a notebook and if there is a change needed for next year make a note at harvest time.

-- Is there a source of information by plant type for proper spacing of plants using this method? -- I am not sure what you are asking. You are on the Sq Ft Gardening forum and asking if there is a spacing guideline for deep raised beds. Of course there is. You can go with the spacing in the Square Foot Gardening Book or the spacing in the Cubed Foot Gardening book which is based upon Sq Ft Gardening but uses 12" rather than 6" beds. Alternately you could go with "WORD, The Vegetable Gardener's Bible" which focuses on deep dug (into the ground) raised beds. In the end it is just different ways to the same end. Take your pick.

Scrap wood is certainly fine and it what I use in my garden. First make sure the box is located where it will get at least 6-8hrs of direct (no shade) sunlight, not daylight but direct sun. If you stand between it and the sun you will see your shadow. It looks like there may be some things nearby that will block the sun. < I should get a tomato cage for the tomato plant, right? Do the peppers need anything?> You can try the cages on the pepper plants, often the soil is too soft to support tomatoes in cages but can work for peppers which won't get as big or heavy. But for tomatoes I like Upright supports screwed to the side of the bed. I found some links from days gone by but feel free to search for more. http://forums.gardenweb.com/discussions/2162223/can-tomatoes-and-peas-climb-twine Vertical Support Not sure which side is North in your photo but make sure you plant your taller plants (tomatoes) on the North side. This is so the tall plants don't block the sun. Spacing can be taken from the seed packet - use the seed spacing after thinning since you won't be thinning. Draw it out on paper to see if you will have room for what you have planned. Keep a Garden Notebook. Each spring review what went well last year and what needs improvement. Winter is a good time to plan the next garden layout, plants, etc. Start small and try to avoid overcrowding. If you want more plants next year make another box. Cherry tomato plants tend to grow very tall (vines) and will provide lots of tomatoes. I am so glad you are teaching your son to garden. Kids are like sponges and learn so quickly then will ask you questions you never ever thought of to make you think AND learn. HTH and good luck. Any other questions?