Green Thumbs Up: Plant annual flowers for summerlong color

Suzanne Mahler

With the passing of the summer solstice, summertime activities shift into high gear. For many, the summer months are a time for beaches, boating, golf, vacations and family gatherings around the backyard pool or patio.

Homeowners continue to manicure their lawns and gardens for their backyard summer events, and for those who love flowers, we are always on the lookout for just a few more colorful accents to highlight our living spaces or add a touch of color to an all green shrub border. Even a trip to the grocery store requires a momentary pause to browse through the assemblage of plants that surround the entry.

For more than 30 years, perennials have been my primary passion, but despite my love affair with these diverse, long-lived plants there are admittedly lulls in the border during the summer months. While the color and texture of foliage play key roles in filling these flowering voids, I have become increasingly lured to the showy annual flowers to bridge these gaps.

During the latter half of the summer when the majority of trees and shrubs have finished blooming and perennial color often declines, free-flowering annuals come into their glory, offering a variety of habit and size and a wealth of color. During this season of especially early and condensed bloom, annuals will become invaluable sources of late summer color.

Botanically speaking, an annual plant completes its life cycle in a single season, but many plants encompass our definition of annuals, including summer bulbs, tender perennials and tropical plants. The possibilities are numerous, and despite the popularity of the familiar and reliable impatiens, geraniums and marigolds, many equally rewarding annual plants are readily available.

Annuals are wonderful companions to perennials, shrubs and vegetables. As they lack the complex root systems of long-lived plants, they are relatively undemanding of water and nutrients, allowing them to be readily tucked into beds and borders among established plants and making them ideal for use in containers. Given good light, consistent moisture, reasonably good soil and regular removal of spent flowers, annuals will offer summerlong color.

They are valuable for bridging gaps in perennial color and are particularly useful for filling voids in new perennial borders until young plants mature. As the foliage of spring-flowering bulbs declines, annual transplants can be introduced to camouflage the fading leaves and cover the bare spaces left behind.

A profusion of annual and tender tropical plants is available at our local nurseries to provide spectacular color throughout the summer months. The majority of these summer beauties require six to eight hours of sun to flourish. Garden soils that are well drained with moderate humus content are preferred. Annuals require about an inch of water a week to thrive, and supplemental watering may be necessary when Mother Nature does not provide.

Each season, I experiment with new color combinations as I plant a narrow strip along my back walkway, tuck annuals into my perennial borders, and create ribbons of color along their perimeter. For taller accents, I adore the spidery blooms of cleome, its spiny stems elongating all summer with white-, pink- or violet-tinted blooms. Look for multicolored cosmos with daisy-like blooms and fine feathery foliage, tall ageratum with fuzzy lavender-blue blossoms, sunflowers and tall varieties of zinnias, dahlias and marigolds.

For sandy soils, lantana is a winner with multicolored blossoms that attract butterflies and hummingbirds. Cleome, geraniums, Mexican sunflowers (tithonia), celosia, the silvery-foliaged dusty miller, globe amaranth (Gomphrena), sweet alyssum, calendulas, nasturtiums, portulacas and gazanias all tolerate and often perform their best given drier conditions.

Shady sites pose a greater challenge for growing nearly all flowering plants, especially where the roots of woody plants make digging a hole a formidable task.

Annual transplants are often an ideal solution for bringing a touch of summertime color to these areas of dappled shade. Their compact root systems enable gardeners to tuck them here and there among trees and shrubs. Given a few hours of filtered sunlight, many will survive and thrive throughout the summer months.

Impatiens are by far the most popular plants for this purpose due to their prolific flowering, vibrant colors -- plus, they do not require deadheading. Their cousins, the New Guinea impatiens, offer larger blossoms. While touted as being sun-tolerant, I find they perform best in filtered sunlight. Wax begonias offer carefree, compact, fleshy plants smothered in pink, white or red flowers. Other members of the begonia family are equally valuable additions to the shady garden, especially the showy tuberous begonias. Fuchsias and wishbone flowers (Torenia) are personal favorites as they thrive in partial shade in addition to attracting hummingbirds.

Perhaps my greatest addiction to annuals in recent years comes in the form of coleus. These stunning foliage plants are easily grown in partial shade to full sun, as bedding plants or in containers. Exotic leaves in shades of purple, red, pink, salmon, gold, bronze, rust and chartreuse. Many require direct sun for at least part of the day to demonstrate their brilliant multi-colored tints.

Sun-lovers like dusty miller, dianthus, blue salvia and snapdragons may survive a mild winter while cleome, bronze-leafed perilla and portulacas, and annual poppies often seed about the garden providing color in subsequent seasons.   

Our local nurseries still have a wide selection of colorful annuals available. Use your imagination and add pizzazz to your doorstep, patio or deck with colorful, portable container gardens or plant a ribbon of showy annuals along the edge of a perennial garden or shrub border. As the summer progresses, these flamboyant additions will provide welcome season-long color.

Suzanne Mahler is an avid gardener, photographer and lecturer who has been developing the 1.5-acre property surrounding her home in Hanover, Mass., for more than 30 years. She is a member of two local garden clubs, past president of the New England Daylily Society, an overseer for the Massachusetts Horticultural Society and is employed at two garden centers.