In the Garden:
Coastal and Tropical South
August, 2010
Regional Report

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3549

Black-eyed Susan, Rudbeckia hirta, has taken over the space it used to share with purple coneflowers and Stokes' asters (Stokesia).

Rugged Perennials

Horticulturally speaking, perennials are plants that are expected to survive for 3 years or more. From the garden perspective in our zones, perennials are plants with green stems, not woody types that may or may not die back to the ground each year. Or, as the classic garden joke goes, a perennial is a plant that, had it lived, would have come back to bloom again for several years.

Design strengths
We use perennials to establish rhythms of color and form in beds and borders. As a well-planned design brings a succession of perennials into bloom, we are drawn to the changes each week brings. Spring's polite chorus of colorful flowers becomes summer's rock opera of bold flowers and forms. To illustrate this point, consider the design of a truly pleasing botanic garden's perennial border. Early spring plantings may feature beautiful but subtle perennials like Lenten rose (Helleborus orientalis), carpet bugleweed (Ajuga), native columbine (Aquilegia canadensis), and sweet alyssum (Lobularia maritima). Soon, however, they give way to striking daylilies (Hemerocallis), bold Shasta daisies (Leucanthemum x superbum), huge flag iris (Iris pseudocorus), and LA iris. As summer comes into its full glory, the perennial bed becomes a riot as gingers (Zingziber), cannas, salvias, mallows and hibiscus take center stage. The perennial plant palette for our regions is extensive and these are but a few examples of the possible combinations.

Timely beauties
Perennials are among the most predictable of the plant groups, and so we rely on them to bloom at an expected time. Most often they deliver, but in recent warm years the time lines have changed for some. Reports are that red hot poker plants (Kniphofia) and garden phlox bloomed out weeks ahead of schedule this year. Indeed, those who keep bloom time calendars have noted 7-10 day acceleration in many species over the last decade. This trend may lead to more perennials planted as individual clumps. Mass plantings that bloom unexpectedly can be much more distracting to the overall design of a landscape than single clumps.

Where we grow
Every property falls into one of 4 basic categories: sunny and wet, sunny and dry, shady and wet, or shady and dry. Get to know the differences between areas of your landscape and pick perennial plants to suit the situation. The time it takes to bone up on the plants you'd like to grow will be repaid many times in lower maintenance. For example, areas that stay wet much of the year are perfect for LA iris and white spider lily (Hymenocallis). If you put them into a well-drained bed, they will require supplemental irrigation. Planted in a more naturally appealing environment, these marginal bog plants will also spread to fill as much space as is suitable. Some perennials seem to survive anywhere. Cast iron (Aspidistra), common yarrow (Achillea millefolium) and many aloes can literally grow in gravel. From sandy soils to heavier clays, these perennials make it look easy. Others come right from the roadside to our gardens, such as cross vine (Bignonia capreolata), yuccas, pink evening primrose (Oenothera) and door yard plant (Ruellia). In the last century, these plants were not even considered for garden culture by most horticulturists. Like glory bower and blue butterfly bush (Clerodendrum), they have been embraced recently and often appear at plant swaps and local sales. Occasionally, one even makes it to the garden center.


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