Start your project in early to mid-spring for fair, sunny working weather and the best range of planting choices. Most summertime vegetables and annuals start well with night-time temperatures of 55 to 60 degrees Fahrenheit.
Find a wall that gets bright sun exposure and good air circulation all day. South-facing walls receive good sunshine and protection from harsh northern winds.
Use commercial rain gutters as your planters. Drill holes in the bottoms of the gutters every 3 to 4 inches for drainage. Put the gutters against the wall with 2 to 3 feet of vertical space between each gutter, and secure them with a hammer and nails. Use a hammer gun for hard concrete walls. Place the nails every 2 to 3 inches for security.
Mix a rich, moist and supportive planting mix of 1 part organic compost to 1 part potting soil or garden loam. Treat these plants as potted plants with more generous nutrition and water needs in their soil. Add 5-10-10 or 10-10-10 granular fertilizer to the mix for better starting nutrition.
Plant small herbs and annuals in this situation. Alternatively, choose contained-growth vegetables such as lettuce, cabbage, broccoli, radishes, endives, collards and baby carrots.