Don't worry. If you run out of room, just pull out the under-performing plants and forge ahead. One zuke is more than enough for a family of four for fresh eating and it'll start producing long before it gets huge. You can always succession plant -- so when the one zuke gets bigger and production starts to taper off, the replacement is getting big enough to flower. There's also a climbing zuke that likes growing in containers, but I haven't tried it. When I lived in California and had a small patio, I gardened square foot style. Most everything grew with precision and exactly as the books and web sites say. In Alabama? I think there's steroids in the dirt. I get monsters here. I experimented with small melon plants last year, and Minnesota Midget really does live up to the description but all the melons ripened at once and then the plant died. I got 5 4-5" melons off a tiny little plant with a couple of 4' vines, though. This year I am trying a reportedly smaller zuke plant (cocozelle) and smaller winter squash varieties. I have lots of room but the BF doesn't eat many veggies and I need smaller portions!

If you build your beds on top of your existing soil, with landscape fabric covering the ground, the weeds should be less of an issue. Then build your mix on top of that. That's what I did, but added 3 inches of gravel over the fabric for better drainage and weed control. I'm lucky here that we've got a regional composter that uses no less than 5 types of plants for compost and thousands of different source plants, so it's as diverse as you can get. And I can get it in bulk from several sources and if I need more than 5 yards, they'll deliver. So I agree, it's much easier in the long run to replace or build over your existing soil. Here is a link that might be useful: Sinfonian's garden in progress...

Personally, I'd plant more spinach in one. The other, I'd try for something else leafy - even better if the roots are edible too! Nasturtium is fun, especially for a 2 yr old since you can eat the leaves and the flowers :) We can't get enough Chard in my house! Good luck and hope to hear that it goes so well you become addicted!

If that's the case, wouldn't normal composting and mulching still bring the roots up if planted in the ground (as opposed to a raised bed)? Also, does anyone know whether regular additions of compost and mulch will affect the soil level/height? If it is going to keep raising the soil level, necessitating the need to make the raised beds taller to retain the soil, I'd probably be better off planting them in the ground.