It seems to be human nature to desire what we don't or can't have. That must be why Florida gardeners long for the Holy Grail of blue flowers. So many called "blue" are actually purple or lavender. But there are easily grown perennials and annuals that add a true-blue soothing coolness to our hot, steamy landscapes.
Perhaps the most effective blue-toned perennial for sunny gardens is ''Mystic Spires'' salvia, a dwarf form of the lovely ''Indigo Spires.'' Its blossom spikes, a rich blue tinged with purple, remind me of an upside-down chandelier. Like many flowers, it is even bluer in somewhat acidic soil. The plant itself is dense and bushy and loves to be cut back by half when it gets a little leggy at the end of summer.
Superb as a long-lasting cut flower, it offers stunning contrast to yellow flowers in an arrangement or in a garden composition. Butterflies and honeybees are drawn to it. You'll see it sporadically at garden centers and at nurseries, so when you see some for sale, snap them up. Mystic Spires is a dream come true for the person who loves blue posies.
Our own native Florida spiderwort (Tradescantia ohiensis) offers upright stalks topped with sapphire-blue flowers that are edible in salads or as plate garnishes. The graceful clumps do best in damp, acidic soil in dappled sun to light shade. Trans-species hybrids exist in pinks, white, purples, lavenders and various shades of blue, but to my eyes the wild species offers the purest blues and reminds us of the value of growing native wildflowers in our landscapes.
A perennial tropical vine with astonishingly rich cobalt-blue flowers is the blue pea vine, known botanically as Clitoria ternatea because botanists see hints of intimate female anatomy in the floral structure. This perennial native of Malaysia is draped with living sapphires nestled into the lush emerald foliage. It just begs to be trained up a mailbox. Both the single and double-flowered forms bloom throughout the year. Petite bouquets last for days, though under artificial light the flowers take on a purple tone. But in natural sunlight, that clear cobalt color is superior to nearly any found in Florida gardens.
Grown easily from the brown pea pods that form as each bloom fades, this freeze-tender perennial, also known as butterfly pea, reaches about 8 feet in height in good soil, tolerates full sun to light shade and will bounce back after a freeze come spring. Save a few of those ripe seed pods for insurance and to share with friends eager for a dash of true blue in their landscapes. (Sources of Clitoria seeds: Sand Mountain Herbs, www.sandmountain herbs.com; Whatcom Seed Co., www.seedrack.com.)
The flowers taste like sweet lettuce, so add them to salads, especially those that also include yellow and orange nasturtium blooms.
Organic gardeners take note: This plant "fixes" atmospheric nitrogen into the soil and is planted on farmlands to be turned under as a green manure. The leaves are used as livestock fodder, in case you raise rabbits or chickens.
Blue ginger, known botanically as Dichorisandra thyrsifolia, is not a ginger at all but a member of the Commelina family and thus related to the Wandering Jew vines. It prefers dappled sun and damp acidic soil but can take a surprising amount of shade. It presents dramatic spikes of a saturated royal blue to cool overheated eyes. Visitors to the USF Botanical Gardens' shady landscape garden are wowed by the lovely established planting of "Blue Ginger" thriving in dense shade, its beacons of sapphire blue luring the eyes into that inviting gloom beneath the spreading oaks. Of course, it is stunning in bouquets, especially with yellow glads or cannas.
Just as easy, yet offering mixed hues of sensual sapphire and violet hues, is the shrub Clerodendrum ugandense. This native of east Africa is showing up more and more in garden centers, looking as if a flock of pastel blue butterflies has alighted in its cheery green branches. Don't be surprised if butterflies actually do visit this landscape gem.
We can't conclude any discussion of blue flowers without mentioning the old-fashioned annual ''Heavenly Blue'' morning glory. Those funnels of the most ethereal sky blue contrast with the plants' white and yellow throats. A $1 packet of seeds can convince children (or adults) that they are great gardeners as the vines erupt and thrive soon after planting. They add a cooling grace even to a decrepit fence or an unsightly chain-link.
We have a few more hot, steamy months to go before winter, so why not at least cool your eyes and soul with true blue bounty?
John A. Starnes Jr., born in Key West, is an avid organic gardener and rosarian who studies, collects, cultivates and hybridizes roses for Florida. He can be reached at firstname.lastname@example.org.