How To Grow Onions From Seedlings In Your Raised Bed Garden | When the seedlings are ready, make holes in your prepared raised bed garden and plant your onion seedlings 4 inches apart on rows. Space your rows 6 to 12 inches away from each other, depending on your raised garden’s size. Easy Garden, Edible Garden, Raised Garden Beds, Raised Beds, Planting Onions, Growing Onions, Easy Vegetables To Grow, Garden Theme, Garden Projects