Raised flower beds allow you to display a wide range of plants. According to Wilson Bros Nursery, choose plants that get the most nutrients out of fertilised soil. The root system must stretch outward rather than extend downward for optimum growth. Most flower beds have 60 to 90 cm (2 to 3 feet) of fertilised soil for each plant's root system to thrive in.
Grasses have a root system that stretches outward in a thick tangle approximately 30 cm (1 foot) below the ground. Because of their root system, ornamental grasses thrive in raised flower beds. The grasses grow between 1.2 and 2.4 m (4 and 8 feet) tall, making great borders and accents in raised flower beds. Common grasses include maiden grass and porcupine grass. Both grow up to 1.5 m (5 feet) tall, allowing for fast growth and low maintenance.
Annual flowers and plants allow for redesigning of the flower bed each year. Their life cycle lasts for one year before producing seed and dying. Most annuals have small root systems because of their short life span, forming a cluster of roots beneath the plant 15 to 20 cm (6 to 8 inches) in diameter. Annual plants are commonly sold at nurseries in small-sectioned containers ready for planting after purchasing. Common annual plants include marigolds, pansies, salvia and petunias.
Perennial flowers and plants grow back each year, often with new shoots of growth allowing the plant to slightly expand. In raised flower beds, perennials will thrive because of the lack of competition from outside weeds and plants. Perennials establish a flower bed, providing a low-maintenance garden which does not require planting each year. The root systems of perennials, larger than those of annuals, require fertilisation more often, though they can easily survive in a raised flower bed. Common perennials include hosta, bee balm, primrose, blazing star and balloon flower.