Pick raised bed vegetables to match the bed, not the other way around. No extension source located ranks crops for beds or publishes a best-of list, so treat any ranking you meet as one gardener's opinion. What the sources do set is conditions. Delaware sets at least 12 inches (30 cm) of soil depth and six or more hours of direct sun, and every source wants soil you keep feeding. Measure those three things first and the crop list sorts itself out.
Depth sets the ceiling for everything else. Delaware Cooperative Extension asks for at least 1 foot (30 cm) of soil to grow a healthy, productive garden. Check your frame against that number before you plan a thing. Vegetable rooting depth is the other half of the match, because roots that run deeper than the box stop at whatever they hit. A bed under 12 inches (30 cm) should have no bottom at all, and then the roots pass straight through into the ground below and borrow the depth they need.
Sun hours are the next filter, and they trip people up because a spot that looks bright at noon can sit in shade by three. Count real hours of direct light across one full day. Six hours a day is the working minimum for a bed, and 6 to 8 hours is the range that gives you maximum fruit and foliage production. Fall short of that and you give up production, since that range is what the source ties to maximum fruit and foliage. Sliding the bed out from a fence line or a tree canopy often buys you the hour you are missing. A spot that clears in June can lose an hour by late summer as the sun drops lower, so count again when the season turns.
Fertility is the third factor and the one that runs down fastest. Vegetables grow fast and pull hard on nitrogen, phosphate and potash, so a bed wants compost on a regular schedule and enough water to carry those nutrients down to the roots. Intensive planting yields come out of that upkeep. A growing bed is the basic unit of an intensive garden, and it returns more per square foot than open rows because the soil stays rich and roots have room to spread. Crowd plants into thin, dry soil and you get the crowding with none of the yield.
Run a tape from the soil surface to the bottom of the frame. If the bed sits open on the ground and holds under 12 inches (30 cm), count the soil below it as extra root room.
Watch the spot through one clear day and add up the hours of direct light. Six is the floor and the useful target sits between 6 and 8.
Work compost in before you plant and top it up through the season, then water enough that the nutrients keep moving toward the roots.
Put the raised bed vegetables that root deepest in your deepest soil and keep the rest in the shallow frames. Nothing published ranks them for you, so go by the two measurements you just took.
Take both measurements before you shop for seed. A 12 inch (30 cm) bed sitting on open ground grows a full garden, so depth stops being the limit and sun becomes the thing to fix. If your only bright spot is a shallow frame on a patio or a roof, build the sides up rather than out, because there is no soil underneath to borrow from. And skip the ranked lists of raised bed vegetables. The ranking that counts is the one your own depth and sun hours hand you.
Read the full article: Raised Garden Bed Specs Backed by Research
