Because they do not like warm weather through summer much, sweet William, Dianthus barbatus, is appreciated more as a cool season annual from autumn into winter and even into spring. They can also be planted early in spring for color before summer warmth. They can sometimes survive as perennials in sheltered areas, particularly if mixed and hidden amongst other perennials and annuals. Deadheading (removal of deteriorating flowers) prolongs bloom.
New plants are easy to propagate from division, cuttings or layering of tired older plants. (Layering involves rooting prostrate stems by burying them slightly and them separating them when they have developed roots.) By the time the old plants become too deteriorated to salvage, the new cuttings or layers should be ready to replace them. New plants like to start out in rich and well drained soil, but not watered too much since they can be susceptible to rust and fusarium wilt.
The white, pink, rosy pink, red, somewhat purplish or bicolored half inch wide flowers form rather flat dense trusses on top of short stems. Minute but abundant green bracts fill the spaces between the individual flowers. The rich green leaves below are about an inch to two and a half inches long. Mature plants of the more common varieties are typically less than a foot tall and wide. More compact and larger varieties are available as seed.
Calendula dislikes summer warmth and may not last completely through winter, but should last as long as marigold.
What was probably the last of the warm weather for the year really got the zinnias going again; but only for their leaves to become dusted with powdery mildew in the subsequent long cool nights. No matter how good the zinnia flowers still look, it is time for cool season annuals.
In mixed plantings, cool season annuals can be ‘plugged’ (as seedlings or small plants) or sown (as seed) among the warm season annuals so that they are ready to perform as the warm season annuals succumb to cooler weather. Of course in more uniform beds, warm season annuals will eventually need to be removed to make space for their cool season replacements.
Pansies and related violas are likely the two most popular cool season annuals. They fill in nicely as bedding plants or are nice components to mixed plantings. They perform best early in the season while the weather is still a bit warm, but should last until the weather gets too warm the following spring.
Primroses and Iceland poppies can take a bit more effort since they need ‘deadheading’ (removal of deteriorating flowers) to continue blooming. Primrose can also be hazardous to anyone who happens to be allergic to them, causing skin irritation comparable to that of poison oak! Some primroses are very brightly colored, while others are more subdued and elegant shades of pink and white. Iceland poppies are mostly pale shades of orange, yellow, pink and white on wiry stems.
Chrysanthemums, which are actually perennials, are the most variable of the cool season annuals, with a wild range of colors and flower forms. The varieties most popularly grown as annuals stay low and compact. Taller types make good cut flowers, but are not so practical for bedding. The related African daisies, which are incidentally similar to the ground cover of the same name, lack the variety of flower color and form, but are easier to grow; particularly as a perennial long after other cool season annuals are gone.
Calendulas are another simpler chrysanthemum relative that are more proportionate to typical annuals, since they get only a few inched deep. They would probably be more popular than they are if they provided more colors than their marigold like orange and yellow. Unlike chrysanthemums and African daisies, calendulas really are annuals, so do not last long into warm weather.
Red, white, pink and rosy pink flowers among rich green foliage can be provided by sweet William (dianthus). They not only tolerate a bit more shade than some other cool season annuals, but are also likely to survive sporadically as perennials where protected from warm exposure through spring and summer.
Stock is the best cool season annual for fragrance. It smells like carnations, but much stronger. Short varieties are good bedding annuals, and even better for mixed plantings. Taller varieties are great cut flowers.
French marigold is one of the most popular annuals of autumn. Pot marigold, Calendula officinalis, provides similar color with daisy like flowers. Most are bright orange or yellow. They lack only the warm burnished red of French marigold. They compensate with more variety of their pastel ranges. Their single or double blooms are two to three inches wide.
Within cooler climates, pot marigold blooms between spring and late autumn frost. Here, it blooms better through mild winters, with only minor pauses for any mild frost. It is more likely to dislike summer warmth. Like many seasonal annuals, it can technically grow as a short term perennial. However, also like others, it performs best for a particular season.
During their season, taller varieties may grow a bit higher than two feet. Most are shorter. Their oblong and slightly fuzzy leaves are mostly between two to five inches long. Some develop wavy margins. Mildew is sometimes a problem. Deadheading promotes bloom. However, a few deteriorating flowers can remain to provide seed for another generation. Subsequent generations eventually revert to simple and single yellow or orange bloom.
There is no rush yet. Some cool season bedding plants can go into their gardens as late as autumn. Ornamental kale and cyclamen can be as late as winter if necessary. Locally, autumn and winter can be a bit later than elsewhere. Also, different cool season bedding plants rely on different schedules. Ornamental kale and cyclamen actually prefer to wait.
Cool season bedding plants are the same as winter bedding plants. They also qualify as cool season annuals and winter annuals. However, most have potential to be perennial, and some can perform after winter. Some are warm season bedding plants within cooler climates. Locally warm summers and mild winters limit their performance very differently.
All bedding plants provide a profusion of temporary floral color for their assigned season. Cool season bedding plants replace deteriorating warm season bedding plants. Within a few months, warm season bedding plants will become seasonal again. Most that can be perennials are disposable for simplicity. Replacement is generally simpler than salvage.
Installation of bedding plants is often contingent on performance of their predecessors. If petunias of last summer still bloom nicely, pansies for autumn may need to wait. Pansies might need to be early though, if petunias are already shabby. Most cool season bedding plants are fortunately adaptable in that regard. Merely a few must wait for cooler weather.
Scheduling for seeding of cool season bedding plants is not as adaptable. Seed can not germinate and grow faster if late. Actually, seedlings grow slower as weather gets cooler. Seedlings for some species should be growing already. Others should start about now or rather soon. Some should start in cell packs or flats. Several others prefer direct sowing.
Pansy and viola are probably the most familiar and reliable cool season bedding plants. Marigold and perhaps snapdragon are popular now, but may not perform through winter. They become seasonal again as winter ends. Sweet William and a few sorts of primrose are potentially perennial. Any that survive through summer could resume blooming soon.
Tony Tomeo 