Timing the Blooming of Perennials

The most important single aspect of perennial gardening is timing the bloom. When designing with perennials, it is essential to know when each plant will bloom and for how long. Different perennials bloom at different times throughout the season and for different lengths of time. The challenge is to get them to coincide. Bright yellow daffodils and dark blue dwarf delphiniums would make a lovely combination, but the daffodils bloom in early spring and the dwarf delphiniums in midsummer. It is critical to coordinate the timing to produce combinations that work. This is the most interesting, most challenging, and most exciting aspect of perennial gardening

This coordination is crucial because perennials generally bloom for two to four weeks, a much shorter time than annuals, which typically bloom from spring through summer into early fall. (Note that there are many exceptions among perennials, and these exceptions may bloom for a much longer time. For example, chrysanthemums bloom from August to November.) To extend color over time, select plants with different blooming times or lengths of bloom. If, for instance, the goal were to have a red and yellow combination in the garden from spring to fall, the first combination might be red and yellow tulips from March through April, followed by red-hot-poker (Kniphofia uvaria) and yellow coreopsis from June through July, succeeded by cardinal flower (Lobelia cardinalis) and golden groundsel (Ligularia dentata) in August, and yellow chrysanthemums with showy stonecrop (Sedum spectabile ‘Autumn Joy’ or ‘Meteor’) from September to November.

Some gardeners select flowers that all bloom at approximately the same time for a garden filled with color. This creates a spectacular, but brief, display. Unfortunately, it also means there is little or no perennial bloom for the rest of the season. Other gardeners prefer a longer duration of color and plant for a continuous succession of bloom, with new flowers coming on as others fade past bloom. This dilutes the effect of the overall garden color. It does, however, reveal rather more of the character of the plants. In general, even when the garden is planned and planted for a succession of bloom, there are three or four peak periods during the season, interspersed with periods of green quietude.

Although it may be difficult to envision these changing patterns, a time-lapse film of a perennial border taken from early spring to late summer would clearly show one wave of flowers replacing another. To select perennials for a succession of bloom, use the chart in Bloom Season of Perennials, which illustrates clearly how various perennials relate to one another in terms of when they bloom and for how long.

With the variations in blossoming times and duration of bloom, the possibilities of the perennial garden are immense. Add the challenge of coordinating color to that of coordinating time of bloom and length of bloom, and the possibilities become even more immense, so great that they may intimidate the beginning gardener. You might ask, Why bother with all this? Why not merely plant annuals for a full season of bloom? The simple answer, apart from the uniquely attractive characteristics and longer life of the perennials, is that the perennial garden planned for a succession of bloom is always changing. The perennial garden is not one garden for one year, but many gardens in one for many years.