If you’re new to urban gardening and want the simplest possible start, choose loose-leaf lettuce. It is forgiving, quick, and well suited to the limited depth and changing light of a planter box. Unlike vegetables that need deep soil or a long season, lettuce grows happily in 6–8 inches of potting mix, germinates fast, and can be harvested leaf by leaf. That means you don’t have to wait for a full head to form before eating.
Use a box with drainage holes, fill it with light potting mix, and sow seeds thinly about 1/4 inch deep. Keep the soil evenly moist but not soggy. A spot with 4–6 hours of sun is usually enough, though lettuce appreciates afternoon shade in hot weather. Thin seedlings so they have room to grow, or snip young leaves as a mini salad. For a steady supply, sow a small pinch every two to three weeks instead of planting everything at once.
Loose-leaf lettuce also works well on balconies, patios, and small rooftops because it stays compact and does not need staking. Pick outer leaves first and let the center keep growing; this cut-and-come-again method gives you multiple harvests from one planting. If you want a backup crop, radishes are another very easy option, but lettuce is the most beginner-friendly overall.