Perhaps no flowers have seen such dramatic improvement in their suitability to Southern gardens in recent decades as petunias. They've long been mainstays in borders and containers because of their profuse blooming and incredible range of colors. But they just didn't stick around long enough to suit us. Our hot, humid climate meant their flowers often melted and entire plants died by midsummer.
Petunias used to be divided into two groupsGrandiflora (large flowers on a bouquet-shaped plant) and Floribunda (medium-size flowers on a compact, mounding plant). Neither group liked our weather and pretty much became superfluous. While you can still get improved, large-flowered specialty petunias in a wild assortment of colors and patterns (as well as generic petunias sold by color in big box stores), by and large gardeners have turned to a new category of hybrids that we like to call Landscape petunias.
Landscape petunias have slightly smaller flowers than their predecessors, but lots more of them for a much longer time. Whether mounding or trailing, they're dense and full. Their biggest advantage is that they tolerate our Southern climate. In most places in the South, they'll bloom continuously from spring until fall and don't need deadheading. Plant them in masses or grow them in containers.
Four of our favorite groups of Landscape petunias are described below. Two are grown from seed and two from cuttings. Cutting-grown plants are said to be more uniform and reliable. However, since seed mixes are refined and improved each year, average consumers likely won't notice any difference.
Wave petunias. Seed grown. Wave petunias blazed the trail for better performing petunias with the introduction of the landmark Purple Wave petunia in 1995. It hugged the ground at only 57 in. tall and spread up to 48 in., making it possible to create a ground cover of petunias. It's now included among other colors in the Wave Classic series. Other Wave series include Shock Wave (710 in. tall, 36-in. spread, dazzling colors), Easy Wave (612 in. tall, 30- to 36-in. spread), and Tidal Wave (mounding plants 1622 in. tall, 30 to 48 in. wide). Tidal Wave Silver is an exceptional performer in the South and may survive a mild winter to show up the following year.
Supertunia petunias. Cutting grown. Supertunias are vigorous, mounding, dense plants that fill the garden with flowers. They grow 1624 in. tall and 1824 in. wide. Our favorite is 'Supertunia Vista Bubblegum'. It's a gardening superstar; its bubblegum-pink flowers can probably be seen from space.
Surfinia petunias. Cutting grown. Surfinias are very low-growing, trailing plants. They grow only 36 in. tall but can spread up to 4 ft. Blooms don't form just on the ends of stems, but all along the stems, so you end up with a mat of solid color.
Picobella petunias. Seed grown. These dwarf plants sport abundant 12 in. blossoms on small, mounding plants that grow 1012 in. tall and wide. Great in smaller garden and in containers.
Species petunias. All modern petunias have as their ancestors the following two species. Violet petunia (P. violacea, also listed as P. integrifolia) hails from South America. This trailing plant boasts multitudes of rosy purple, 1-in. flowers with dark throats. It blooms nonstop from spring to fall and is outstanding in window boxes, pots, hanging baskets, and planters. It's very heat tolerant and usually winter hardy from the Lower South down. The selection 'Laura Bush' grows 1824 in. tall and its flowers are twice as big. White petunia (P. axillaris) sports fragrant, 2-in. flowers of white to blush pink. Native to the U.S., it self-sows readily and sometimes naturalizes in fields and country gardens.
Petunias thrive in sun and rich, well-drained soil. Space them 818 in. apart, depending on plant size. Feed large-flowered kinds monthly during the growing season with a bloom booster liquid fertilizer. Hungry landscape petuniasreferred to by growers as the teenage boys of the plant worlddo best when given controlled-release fertilizer at planting time in addition to weekly applications of liquid fertilizer. Cut back leggy plants to force new growth and blooms.
In Florida, grow petunias as winter annuals. Plant them in fall, enjoy their flowers through the cool months into spring, and then replace them with summer flowers that take the Florida heat.
Just a few pests bother petunias, including slugs, snails, and tobacco budworms. Botrytis gray mold can mar the blossoms and foliage during cool, wet weather.