Petunias

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Cherry Cha-ching

By Kim Willis

 

Are you a plant snob?  I once heard someone remark disdainfully that someone else wasn’t really a gardener because she planted petunias.  When shopping at a nursery one time with petunias in my cart I had an acquaintance come up and ask me why I, of all people, was buying petunias.  I was buying petunias because I like petunias and there are so many beautiful ones out there.  I can’t help myself, I buy some every year and I’m proud to plant them.

There is nothing wrong with having petunias in your garden.  Yes they were once the most common garden annual planted.  Older varieties of petunias had to be dead headed and pinched back to keep them blooming all summer and rainy weather turned them into a mess.  But that doesn’t mean petunias don’t belong in modern gardens and modern varieties are much easier to care for than your grandmothers’ petunias.

Modern petunias trace their genetics back to two major native species, P. axillaris which has large white flowers and is pollinated by moths, and P. inflate which has small purple flowers and is bee pollinated.  Another petunia, P. exserta, has small, true red, star shaped flowers that are pollinated by hummingbirds.  It is sometimes sold by nurseries.  A close relative of petunia, the Calibrachoa, is also gaining in popularity.

Through centuries of domestication and hybridization we have the beautiful petunias we know today.  Petunias belong to the Solanaceae family, which includes peppers and tomatoes.  They are native to South America.

Petunias are excellent choices for containers in sunny hot places, in window boxes and hanging baskets and as a groundcover in sunny areas.  Hummingbirds are attracted to some petunias; I always set out a pot of red petunias, Petunia exserta if I can find it, for them.  Bees and butterflies are moderately attracted to the plant.

Petunias are generally grown as annuals; actually they are short lived perennials in frost free climates. In a heated, well- lit greenhouse you might  be able to over winter a petunia but they don’t over winter well in household conditions.  Gardeners in the far south, zones 9 and above, have reported petunias over wintering in the garden.

Petunias have pointed oval leaves.  The leaves and stems are covered with tiny white hairs, and the foliage has a sticky feel to it.  The flowers have fused petals forming a funnel shape.  Flower size ranges from 2 inches across in some varieties to 6 inches across in others.  There are also double flowered varieties. Some petunia flowers are fragrant, particularly purple and blue colored ones.

Cultivated petunias originally came in two colors, white and purple.  They now come in every color imaginable, even a very dark red purple that looks black.  There are star patterned and striped petunias and the newest color pattern is spotted, the petunia ‘Night Skies’  which is deep purple with white spots is an example.  I am old enough to remember when the first true red petunia came on the market, and then the yellow and orange varieties.

Multiflora, Grandiflora, Milliflora, Floribunda, Supertunia, Wave, Surfina, Sweetunia, Tiny Tunia, are some of the “classes” of petunia flowers.  The first four are older types and are the kinds most often planted in the ground in mass.  These can still be found in flats and cell packs for purchase.  Newer varieties are most often used in hanging baskets and containers and are often sold in individual pots. Most petunias have a cascading, vining habit. 

Night Skies

Cultural needs

Petunias need full sun conditions in the north to do their best.  In the south they may do fairly well in partial or light shade.  Petunias are known for being tolerant of heat and drought when planted in the ground.  In containers however they must be watered regularly.  Petunias planted in the ground probably won’t need watering unless it’s been very hot and dry and they are wilting.  Petunias prefer slightly acidic conditions in their native countries, but modern varieties adapt to most types of soil.

Most gardeners will want to start with small petunia plants.  Petunias grow rapidly and small plants quickly become larger.  If the petunias are in small cell packs the best plants to pick are compact ones just starting to bloom.  Lanky petunias with many blooms in a cell pack are stressed and may not do well for a while after planting.  In pots petunias that are full yet compact, with a few blooms are the best choices.  Do not plant petunias outside until all danger of frost has passed.

Gardeners can start petunias from seed.  You need to start about 12 weeks from your last expected frost for good sized plants to transplant outside.  Petunia seed is very fine. Sprinkle it on a sterile seed starting mix that has been moistened.  Press seed lightly into the medium but do not cover as petunia seed needs light to germinate.  Bottom heat is recommended for germination, as is watering from the bottom. Seedling petunias need to be in a sunny warm greenhouse or under grow lights.  They rarely develop well on windowsills.

When planting don’t place the plants deeper than what they were growing in the original container.  Use a slow release granular fertilizer mixed into the soil at planting.  Modern petunias need regular fertilization to do well.  If you don’t use slow release fertilizers you’ll need to fertilize weekly with water soluble fertilizer.  Do not use Epsom salts on petunias.

Modern petunias don’t need dead heading (picking off dead flowers) to keep blooming but they may look better, especially in containers if you do so.   This is especially true of double flowered varieties. Older multiflora and grandiflora varieties may begin to look straggly in late summer and a light shearing back will rejuvenate them for a few more weeks of bloom.

Gardeners seldom run into disease problems with petunias.  Really rainy weather for long periods and water-logged soil can cause various rots and fungal disease as can over watering in containers.  Powdery mildew is an occasional problem.  Good air flow helps prevent this.  If the plants are covered with powdery mildew you could cut them back to 2-3 inches and they may regrow quickly and hopefully without powdery mildew.  Deer and rabbits do like petunias for dessert so be mindful of that.

Some writers list petunias as edible plants.  I would not recommend eating foliage; they are members of the nightshade family like tomatoes.  I would not eat many flowers either, although using them as a garnish probably wouldn’t hurt.