Garden Design – Planning An Herbaceous Perennial Flower Bed

There are a number of reasons why perennial bedding plants, as opposed to annual ones, are used in garden designs. Perennials by growing beyond a single season, are thought to demand less care and maintenance than annuals that have to be replaced every few months or so. In dry climate gardens especially, annual flowers consume significantly more water than any other group of plants, requiring at least 1000 liters per square meter a year, in comparison to some perennial species, which can often grow on a third as much water.

Yet many home gardeners end up being disappointed with their flowerbeds. One reason for this is that in many cases, too many short-lived perennials are planted in the border. Plants like Verbena, Bidens, and Nierembergia, may be splendid specimens, but rarely add much value to the garden after about a year from planting. The answer is to back up the short-lived species with flowering plants that live and look good for a number of years.

For example, The shrubby species of Chrysanthemum, like C. frutescens, can last some 2-3 years before declining. A similar sub-shrub, but more long-lived, is Euryops pectinatus. On the other hand, the grass-like Agapanthus, noted for its fabulous sky-blue flowers that emerge from tall stalks in the summer, spreads by means of vegetative reproduction. The plants can be lifted and divided with ease. Other long-lasting plants include Salvia (Sage), Limonium, Arctotis, Coreopsis, and Lampranthus. (Ice Plant)

Whatever the longevity of a particular species, herbaceous perennials rarely bloom continuously for extended periods of time. There is always an off-season and a time when they have to be cut-down, clipped in some way, or lifted and divided. This is another main source of disappointment. One way round the problem is to include non-flowering herbaceous plants that “hold” the bed, while the showy plants have been pruned down. Phormium, Dietes, Iresine, and the ornamental Asparagus, (Myers Asparagus) are but a few examples of this.

A more creative solution can be found by including ornamental grasses in the composition. The best ornamental grasses like Miscanthus, with their tall plumes and lovely foliage, add dynamic elements of movement and sound to the bed. Invariably, these plants need to be rejuvenated by shaving down to the ground in the spring and autumn. This is where advanced planning comes into its own. Plants that bloom early such as Convolvulus, Osteospermum, Linum, Perovskia, together with a host of well-known favorites, can perform without interference from the tall grasses, and when these latter come into their own at the beginning of the summer, the flowering plants can themselves be pruned back.

Thought should also be given to late flowering perennials that take over from those that have completed their flowering by the end of the spring. Examples include Canna, Penstemon, Felicia, and many species of Iris.