How the Seasonal Color Calendar Works
It is surprising how often you need to replace seasonal color displays. Once a year is not enough. The schedule landscape professionals use for temporary floral displays follows the calendar in a unique way. Plants labeled as annuals do not last a full year, but they can stretch through more than one season. Seasonal color typically needs refreshing at least three times a year.
One way to stretch the effectiveness of a floral display is to replace beds just as one set of annual flowers end their peak flowering period, using cool-season annuals in winter and warm-season annuals in spring and summer, but there are no annual flowers that perform a full six months of the year. Popular annuals have a long bloom period or provide extended color through striking foliage hues, but even with excellent plant choices, there are gaps with a semiannual bed switch.
An annual isn’t called an annual because you plant it once a year. It is called an annual because, if left to its own devices, it will complete a full life cycle sometime within one year. A seed can grow into a full-sized plant, flower, and then go back to seed and die long before twelve months go by. The process often takes only a few months. Corn seeds can be planted, grow to over six feet tall, produce ears, and die in just a few weeks! Annuals can sometimes re-seed in place and repeat the cycle of germination, growth, and seed production, appearing to act as perennials. Most often annuals depend on gardeners to continue the process.
There is no rule requiring you to use only annual species in temporary, seasonal beds. A lot of color-burst professionals include perennials and ornamental grasses to add visual excitement to flower beds. Some use container shrubs and trees, too. They throw out all the plants as if they were spent annuals before each new planting cycle ends. That leaves room for the next, great knock-out combination!
Accepting delivery of annual plants at optimum planting time means buying them when they have a respectable root system, but before they bloom. This allows them to mature for a few weeks with their roots well-established in the beds and provides a better floral display. Wholesale growers help extend the blooming time for landscape beds by starting seed indoors in greenhouses. They bring plants to full, blooming size so retailers can use flower color as a marketing tool and so landscapers can get a head start on the growing season. Professional landscapers prefer to purchase annuals slightly before bloom set, because they know the plants will be healthier without the transplant shock that fully blooming plants suffer when disturbed. By the time a plant is in peak bloom and most attractive for sales, it is reaching the end of its life cycle, and the weather outdoors may become too hot or too cold for the plant to survive long after planting. Timing is everything with annuals.
Landscape professionals can extend the blooming stage by deadheading. Bolting is an ongoing problem with annual flower beds. The telltale sign of bolting is when a plant suddenly send tall flower spikes from what was compact foliage as the energy expended is stolen from the plant. The vigor of a bolting plant is greatly reduced. If gardeners snip away these soon-to-be seed heads before they set, bolting can be delayed for weeks. Without dead-heading, the plant accepts the life cycle as complete and fades quickly. With dead-heading, gardeners can keep plants blooming for months rather than weeks.
Choosing annuals that need to be dead-headed frequently can be a big mistake for commercial seasonal beds. Keeping fresh blooms on a huge plot of Marigolds or Cut and Come Again Zinnias is time-consuming and tedious. The labor costs of deadheading some annuals is prohibitive in large beds. Most annuals need dead-heading to remove the seed-producing flowers before they are allowed to mature. If you are part of a professional landscape maintenance crew, the choice of which annuals to plant can be crucial. Look for annuals which are self-cleaning and drop any produced seed to save time and money.
There are three types of annuals—winter, spring, and summer. Winter, cool-season annuals are usually planted outdoors in the fall as soon as temperatures remain reliably below seventy degrees. They keep growing through winter until things heat up the following spring. They hate hot weather, and literally melt when temperatures soar over eighty degrees. They can tolerate light frost, but not severe cold. Anything below ten degrees can be fatal, so an extreme cold snap will kill them. The winter annual growing season overlaps the spring annual season.
The overlap of seasons leaves professional landscapers with a dilemma. They must choose between allowing winter annuals to mature to a glorious, peak bloom or establishing spring annuals in the soil early enough to get good color by May. A winter bed of Tulips and Pansies, bordered with evergreen Parsley, looks good in March, and if you cut back all the spent Tulips in early April, the Pansies and Parsley will continue to grow lush and quickly fill in any empty spots. Then the Pansies will bloom prolifically from mid-April to late May. Even though early-planted spring annuals flower a bit earlier than ones planted in early June, I recommend a delayed switch to avoid missing the peak for Pansies. The very best blooms of winter annuals come in early to mid-May, and by waiting to plant spring annuals, you avoid a late cold snap killing back or taking out baby spring transplants.
Spring annuals should be planted outdoors as soon as all danger of frost is gone. They tend to be slow-growing until the soil temperatures warm to sixty degrees or more. They provide weeks of color. By the middle of the warm season, in late June, things get very hot, and most of the spring-flowering annual plants are worn out. Sometimes you can revive them for a second flush of bloom in late summer. If you cut back these frazzled plants by about ½ their height, they might spend a few weeks recovering and then bloom again. Most spring-flowering annuals refuse to re-bloom after the weather gets hot, though. Their lives span from the beginning of frost-free days to the beginning of the dog days of summer, in most cases.
Summer annuals love hot feet and sunshine. These late-season annuals can be expected to bloom from mid-summer through fall frost. Many reseeding fall wildflowers are late bloomers and might not germinate until the soil temperature heats up to the mid-seventies or eighties. Asters, Chrysanthemums, and landscape Zinnias fill the color gap between spring and winter and carry a floral bed beautifully through to fall planting season for winter annuals.
So the annual calendar year runs like this:
• Late Winter/Early Spring – Cool season annuals are in all their glory and Spring-flowering annuals can be started from seed indoors
• Spring – Warm season annuals can be planted outdoors and expected to bloom until the dog days of summer. Cool season annuals begin to die from the heat.
• Mid-Summer – Spring annuals are spent and need to be cut back. Late summer annuals can be seeded. This time of year can be a quiet time for annual color in permanent plant beds.
• Late-Summer/Early Fall – Summer annuals are in all their glory until frost. Winter annuals can be started.
• Winter – Winter annuals are alive, but not really at their best. They are busy developing strong root systems and trying to survive cold snaps. This is a good time to supplement winter flowering beds with holiday decorations.
For professionally-planted flower beds, there are three main planting periods. The long winter, spring, and late summer. Seasonal color planters are usually changed out in Oct/Nov, then April/May, and finally in June/July. Annual color provides three seasons of glory. If you are designing a landscape with beds for seasonal color, you need to include a planting scheme for each of these three periods, and budget for complete change within planters and beds at least three times during the year.