An exception to this rule would be where a shorter bulb emerges and blooms early before the plant located in front grows large enough to screen it. Once the bloom period is past, the larger, front plant will screen the maturing foliage of the shorter plant. A tall lacy plant can be treated as a short plant since you’ll be able to see other plants through its foliage. Tall growing tubers like tall dahlias should be used in the corner of the garden or yard where they are viewed from a distance. The dwarf types can be used as facer plants.
Remember that a tall, bushy plant may look short and spindly for the first year or two. Try planting a group of young plants and thinning them out as they mature, or fill in the empty spaces with annuals or some bulbs you lift in fall, like Begonias, Dahlias, Gladiolus, Cannas. To keep the garden interesting, try providing a variety of sizes all season long.