The ever-reliable petunia

Petunias, a summer classic, come in most every color. - cobalt123/Creative Commons

Petunias made it to the top of the popularity charts with a tried-and-true formula for success. By keeping the flowers simple, the bloom profuse and the growing easy, the petunia has been a summer classic since Grandma’s day.

Cascading from a hanging basket, spilling over the edge of a container, or tumbling down a retaining wall, well-grown petunias bear their trumpet-shaped flowers all summer long with unflagging exuberance. Modern hybridizers have taken the original petunia, a scrubby Brazilian wildflower, and tinkered with it to make the plant more compact, the blossoms larger and the color range more dramatic, pushing the number of varieties well up into the hundreds.

Never satisfied, plant breeders can’t stop toying with this flower. Like a pretty girl with a full dance card, the petunia always seems to have a string of admirers who want to take it for a spin and see if something wonderful develops. The fast and furious production of new cultivars makes for a quick turnover of stock in the petunia trade.

Every spring, garden centers are awash in petunias with new colors and yet another round of snappy new names, while many older varieties become obsolete and disappear. Proving there occasionally is something new under the sun, the first black petunias recently mad their debut to great fanfare. There is hardly a color you can name, though, that is absent from the petunia palette.

A “rose is a rose is a rose,’ Gertrude Stein famously said, but with petunias the name game is a little more complicated. There are grandiflora, multiflora, Supertunia, Surfinia, Ultra and Wave petunias -- and that’s just scratching the surface. Throw in petunia look-alikes called Million Bells or Superbells and you’ve got a confusing crowd of pretty faces, all competing for your dollar.

Is it all just marketing or is there really some reason to pay attention? You might be a confirmed impulse buyer with no criteria other than flower color, but drawing a few distinctions will help you pick plants with more staying power and fewer demands.

The older petunia varieties, chiefly grandifloras and multifloras, will stop blooming if the dead flowers aren’t diligently removed. This is nobody’s favorite job since the plant’s stems are sticky and the spent flowers often slimy. With several large hanging baskets or pots to groom, this “deadheading” chore can get old pretty quickly. FYI: Grandifloras have larger flowers, up to four inches, but multifloras have more blossoms and are better at bouncing back after a drenching rain.

Calibrachoa, the petunia’s little buddy. — Les Serres Fortier/CC

Trademarked “designer” petunias marketed since the late 1990s have one big advantage: The plants flower vigorously and non-stop, and dead flowers drop from the plant on their own. Go for Wave, Supertunia, Cascadia or Surfinia petunias and you won’t be condemned to a summer of sticky fingers. Predictably, all of these cost more than the average petunia, selling for $3 or better apiece.

Botanists are still arguing about whether the plant called Million Bells is really a petunia or just a close relative. Botanically speaking it’s a calibrachoa (kal-ih-bruh-KO-uh) but that’s such a mouthful most people default to the commercial name. Blame it on Antonio de la Cal y Bracho, the 19th century Mexican botanist and pharmacologist who couldn’t resist naming the plant after himself.

Calibrachoa looks like a petunia shrunk to one-quarter size. The plant wasn’t introduced in America until 1992 and there are still relatively few varieties, but it comes in eye-catching colors including orange and terra cotta. There’s no sticky factor as the stems are smooth and no deadheading is required. Calibrachoa pumps out hundreds (if not the millions) of flowers in a season and needs less water than petunias, making it ideal for dry or hard-to-reach locations.

Petunias and Million Bells usually come home from the garden center looking fabulous but can gradually lose steam without consistent care. The secret to keeping them at their peak is regular feeding (at least every other week) with an all-purpose fertilizer. If the stems get stringy with just a few sad flowers at their tips, cut them back by half and wait for the plant to launch a fresh spurt of growth.

Petunias have a testy relationship with water. They need enough at the roots to prevent wilting, but don’t like their flowers and foliage drenched. Overhead watering and rain can make the blossoms close up and sulk or become a bundle of mush. Too much moisture in the soil can lead to ugly root rots or fungus and mold attacks, so a well-drained location is crucial.

Other flowers may capture your interest for a season or two, but you’ll always come back to petunias and their little relatives. They achieved their popularity the old-fashioned way – they earned it.