Stress escalates in the dog days of late summer for both gardens and gardeners. Even if you live in a climate that luxuriates in cool nights, the days are long and often dry. In much of the country, late-summer days are hot, and nights are sultry. Many areas also suffer from prolonged droughts this time of year. The best plan is to join forces with the season rather than fighting it. So relax your pace in late summer, and enjoy the many care-free plants that grow best when it's hot.
Having plenty of color in a late summer garden calls for advance planning, especially if your garden is built around bulbs and perennials. Although daylilies, monkshood, rudbeckia, and several other perennials provide bright mid- to late-season blooms in northern gardens, in hotter areas, colorful plants for late summer are more limited. Look for heat-tolerant annuals, succulent perennials, those perennials that are native to hot, arid climates, and the few late-blooming shrubs that are available in nurseries.
There are also some welcome surprises in store for gardeners this time of year. When you plant magic lilies, you'll see flowers appear within days of a deep, soaking rain in mid- to late summer. In general, however, late summer is often a lull time in gardens. Summer's perennials are past their flowering peak. Some long-performing annuals that you would think you could count on, such as marigolds, temporarily cease flowering during intense heat waves, only to resume with the first break in a late-summer heat wave. And rating asters, chrysanthemums, and golden-rods are waiting in the wings, ready to respond to the shorter days of autumn by covering themselves with purple and golden blossoms. The best way to bridge the flowering gap is to fill the gaps in your garden with long-blooming, heat-tolerant annuals.
Heat-tolerant annuals, such as cockscombs, sulfur cosmos, and zinnias can provide a rainbow of late-summer color, and gomphrenas are always willing to produce colorful papery flower bracts in the hottest weather. In sun or partial shade, annual salvias will respond to fertilizer and supplemental water by sending up a fresh flush of flower spikes.
In fact, nearly all annuals planted in spring, whether in beds or in containers, will be in need of a little pampering by late summer. Spend a little extra time with them, pinching off spent blossoms and old stems, and giving them all a deep drench with a water soluble, balanced fertilizer. The results can be dramatic, including improved leaf color within 2 days, and a fresh flush of flowers 2 to 3 weeks later.
Some Like It Hot
Although they can succumb to the barest hint of frost, plants that have tropical origins are custom-made for the sultry season. Plants from hot climates, such as lantana, canna, caladium, tithonia, and sweet potato vine, grow rapidly and flower abundantly in the heat that causes other plants to wilt and stop flowering. In warm climates, these and other tender perennials are routinely grown in the ground year-round.
But in cold-winter climates these inexpensive plants are treated as annuals, or dug up at the end of the season and overwintered indoors. Grown in sunny beds of moist soil, or in pots of moist soil, caladiums will light up any shady or partially sunny place, and the cascading stems and chartreuse or deep purple leaves of sweet potato vine is the finishing touch for a container garden composed of several species of summer-flowering annuals.
To derive maximum performance from tropicals, be sure to water them often enough to keep the soil slightly moist during their summer growth period. Fertilize them with every other watering, using a balanced, water-soluble fertilizer mixed at half strength, according to the package label. And don't forget that several popular bedding plants are tropicals, too, including impatiens and annual geraniums. Indulged with an extra ration of care, these heat-tolerant plants can pull you and your garden through the hottest season.
Late summer is the season for butterflies and for gardeners who enjoy watching their antics. High on the list of nectar flowers are butterfly bush and lantana, but any nectar is good nectar to a thirsty butterfly. Joe Pye weed flowers often get plenty of visitors. And the show isn't over at dusk. Wait until dark to enjoy night-flying moths in search of the evening flowers of four-o-clocks and fragrant flowering tobacco.
To make your garden even more hospitable to butterflies, stock it with plants that produce flat blossoms, which are easy for butterflies to land on. Plants with daisy-shaped flowers, which make late-season butterfly havens include blanket flowers, cosmos, purple cone-flowers, rudbeckias, and zinnias.