Ornamental · Solanaceae
Petunia
Petunia × atkinsiana
Offer it full sun and steady feeding, and your petunia will pour out color from late spring right up to frost.
Full sun
Every 2–7 days
50–86°F · 10–30°C
70–90 days
Overview
Petunias are a wonderfully dependable choice for a summer bed, blooming their hearts out from late spring all the way to the first frost. They belong to the nightshade family, the same group as the tomato and the potato, and breeders have shaped them into hundreds of hybrids in nearly every color except a true black. You will find them tumbling from hanging baskets, softening walkway edges, and brightening window boxes anywhere a sunny corner needs a lift of color.
Most people first get to know petunias as one of four broad types, and it helps to know which you have. The old Grandifloras carry the biggest, most dramatic flowers, the Multifloras swap size for weather-tough abundance, the little Millifloras stay tidy and compact, and the spreading Wave types roam across beds and baskets while cleaning up after themselves. Once you know your type, you will know just how much deadheading and pinching it asks of you, and there is a good match for every gardener here.
They are forgiving and eager to please, though they do like to eat. Give them full sun, rich soil, and a steady supply of food and water, and they will reward you with months of bloom. Forget a feeding or let a pot dry out too far and you may see leggy stems and only a thin scatter of flowers, but do not worry, since a little food and water soon set them right again.
Care
The short version: full sun, soil kept evenly moist but never soggy, and regular feeding, because petunias are heavy feeders that flower their hardest when they are well fed and well watered.
Light
Petunias flower their best in full sun, ideally six or more hours a day. They will take a bit of partial sun happily enough, but give them too much shade and the plants stretch, flop, and offer far fewer flowers, so a bright spot is worth choosing.
Water
Aim to keep the soil evenly moist but never soggy, letting the top inch begin to dry between waterings. Containers and hanging baskets dry out fast and may want daily watering in summer heat, so give them a quick check often. Soggy, poorly drained spots invite rot, so drainage matters every bit as much as moisture.
Soil
Plant them in well-drained, fertile loam rich in organic matter, and they will settle in nicely. A pH between 6.0 and 7.0 suits them well, and good drainage keeps the roots healthy even through a wet spell.
Temperature
Petunias grow happily across a wide band, roughly 50°F to 86°F (10°C to 30°C). They love summer warmth but cannot survive frost, which is simply why they are grown as annuals in cold-winter climates.
Humidity
Average humidity around 40% to 60% is all they need, so this is one thing you rarely have to fuss over. What matters more than the number is airflow, since still, damp air around crowded plants is what lets gray mold get a foothold.
Feeding
Petunias are heavy feeders, especially in pots, so feed them every two weeks through the growing season and they will keep going strong. A balanced water-soluble fertilizer from spring to fall keeps the flowers coming instead of fading out by midsummer.
Pruning
Pinch young plants to nudge them to branch, and deadhead the spent blooms on older Grandiflora and Multiflora types to keep them reblooming. Cut leggy stems back by about half in midsummer to freshen the plant, though the spreading and Wave types clean themselves and rarely need it, so there is less work than you might think.
Repotting
Container petunias are usually started fresh each year rather than carried on. Keep an eye out for roots circling the pot or poking through the drainage holes, fast wilting between waterings, and stalled growth with fewer flowers, since all of these gently tell you the plant has outgrown its home.
Size & spacing
Plants stand 6 to 12 inches (15 to 30 cm) tall and spread 12 to 35 inches (30 to 90 cm) wide depending on the type. Give the spreading kinds a little room to run, and the airflow that comes with it will help keep disease at bay.
When to plant
Petunias love warmth and simply cannot take frost, so timing is your friend here. Start the fine seed indoors 10 to 12 weeks before your last spring frost, then set the plants out once the cold has passed and the soil has warmed, and they will reward you with bloom from late spring through fall until frost finally ends the show.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 10 to 12 weeks before the last spring frost
- Plant: after the last spring frost when soil has warmed
- Harvest: late spring through fall until frost
Troubleshooting
Most petunia troubles turn up on the flowers and the soft new growth, where pests like to gather and rot can take hold, but nearly all of them are easy to turn around. Catch things early and a quick, gentle response keeps a small hiccup from becoming a big one. Find what matches below, then step in while it still helps, and your plants will pull through.
Quick wilting with dark, soft roots
If a petunia wilts, yellows, and slumps even though the soil feels wet, the trouble is almost always root and crown rot brought on by too much water, and knowing that helps you save the rest. Ease the plant up and touch the roots, since healthy ones feel firm and white while rotted tissue turns brown, soft, and sour. A badly rotted plant cannot be rescued, so set it aside, sort out the drainage, and let the soil dry a touch between waterings on the ones that remain, and they should do just fine.
Fix:
- Remove and discard severely affected plants
- Improve soil drainage and reduce watering frequency
- Replant in well-drained soil or containers with drainage holes
Nibbled buds and torn petals with dark grit inside
If you spot ragged blooms and dark specks, take heart, because this is usually just budworms, the caterpillars of the tobacco or geranium budworm moth that burrow into forming buds. Step out at dusk and peek inside the buds for small green, tan, or reddish larvae and the gritty crumbs they leave. Pick off the ones you find, pinch away the spoiled buds, and dab young larvae with Bacillus thuringiensis before they tunnel deep, and the plant will bounce back.
Fix:
- Handpick and destroy larvae
- Remove and dispose of infested buds
- Apply Bacillus thuringiensis (Bt) or another labeled product targeting young larvae
Silvery flecks on leaves and twisted, faded blooms
A silvery sheen with black flecks and warped petals points to thrips, slim insects that scrape at leaves and flowers, and while they are a nuisance you can absolutely get ahead of them. Tap a bloom over a sheet of white paper and watch the tiny pale or dark specks tumble out to confirm it. Pinch off the worst flowers, treat with insecticidal soap, and set out reflective mulch or sticky traps, since thrips can pass viruses between plants and a little care now saves you worry later.
Fix:
- Remove heavily infested blooms and debris
- Apply insecticidal soap or a labeled insecticide
- Use reflective mulch or sticky traps to reduce populations
Soft gray fuzz on spent flowers and leaves
When cool, damp weather sets in, you may notice Botrytis blight, also known as gray mold, settling onto tired blooms and crowded leaves, and it is nothing to panic over. Watch during humid stretches for the grayish, fuzzy spore patches sitting on rotting tissue. Gently clear the affected flowers and leaves, open the plants up so air moves through, and water low at the base to keep the foliage dry, and the plant will carry on happily.
Fix:
- Remove and dispose of infected flowers and leaves
- Improve air circulation and spacing
- Water at the base and avoid wetting foliage
Crinkled new growth with a sticky, shiny coating
Those little clusters on your tender shoot tips and leaf undersides are aphids, and though they look worrying they are one of the easiest pests to send packing. A firm jet of water knocks most of them loose, and a follow-up of insecticidal soap or horticultural oil handles the stubborn stragglers. Lady beetles and other helpers quietly do a good share of the work, so there is no need to reach for heavy sprays.
Fix:
- Spray plants with a strong stream of water to dislodge aphids
- Apply insecticidal soap or horticultural oil to affected growth
- Encourage natural predators such as lady beetles
Toxicity
Here is happy news for pet owners: petunias are safe. The ASPCA lists them as non-toxic to cats, dogs, and horses, and they pose no real poisoning risk to other animals or to people. The most a curious nibble might bring is a brief, mild stomach upset that soon passes.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can relax if your cat sneaks a taste, because petunia is listed as non-toxic to cats. A cat that gobbles a big helping of any plant might feel briefly queasy, but that is as far as it goes.
Dogs None
Your dog can mouth the leaves or flowers with no poisoning to fear. At worst a large, greedy mouthful might bring a little passing tummy upset that soon settles.
Horses Safe
Rest easy about horses too, since the ASPCA clears petunias as safe right alongside cats and dogs. A few blooms grazed here and there does no expected harm at all.
Rabbits Safe
Rabbits can nibble petunia leaves and flowers without any toxic worry. As with any rich treat a sudden large helping may loosen the gut, so simply keep the portions small and you are set.
Livestock Safe
There is no poisoning danger for cattle, goats, or sheep from petunias. The plant is simply not a toxic threat to grazing animals, so a stray mouthful is fine.
Birds Safe
Petunias carry no known toxin for pet or backyard birds. A bird that pecks a bloom is in no danger, so you can enjoy the visitors without concern.
People Safe
Petunias are not poisonous to people, so if a curious child sneaks a taste there is nothing to fret about. The plant is grown for its color and not the dinner plate, so there is simply no reason to eat it.
No special handling precautions for toxicity are needed, though ingestion of any plant material may cause mild, transient stomach upset in sensitive animals.
Varieties
Petunias come in hundreds of named hybrids, but they gather into four broad groups that shape a plant's flower size, weather toughness, and habit. These are the ones worth getting to know as you choose.
Grandiflora
This is the one to reach for if you love a big, showy flower, with blooms up to 4 to 5 inches across, though those grand petals do bruise easily in rain and rough weather.
Multiflora
If you would rather have plenty of flowers that laugh off a downpour, Multifloras give you many smaller blooms that hold up far better through rain and rough weather than the Grandifloras do.
Milliflora
The little charmer of the bunch, staying neat and compact with dainty 1 to 1.5 inch flowers that are perfect for tucking into small spaces.
Spreading/Wave
A wonderfully easygoing choice, these low, trailing plants spread wide across beds and baskets and tidy themselves, so you can skip the deadheading almost entirely.
How to propagate
You can raise petunias from their tiny seed or take cuttings to copy a plant you already love, and either way is well within reach. Seed hands you the widest variety, while cuttings clone a favorite exactly as it is.
SeedModerate
Germination in about 7 to 14 days; bloom roughly 70 to 90 days from sowing
Growing petunias from seed is a rewarding way to begin, so start them about 10 to 12 weeks before your last frost by scattering the dust-fine seed across the surface of a moist seed-starting mix. Leave the seed uncovered, because it needs light to wake up, and simply keep the mix warm and damp until it sprouts in roughly 7 to 14 days. The seedlings take their time early on and reach bloom around 70 to 90 days from sowing, so wait to move them outside until the frost has passed and the soil has warmed, and they will thank you for the patience.
Stem cuttingsModerate
Roots typically form in about 2 to 3 weeks
If you have a plant you adore, cuttings let you copy it, and it is easier than it sounds. Snip 3 to 4 inch tips from healthy, non-flowering stems, strip the lower leaves, and settle them into a moist, well-drained rooting mix. Keep them warm and humid and roots usually appear in about 2 to 3 weeks, and once they do you can pot each little cutting up on its own.
Myths
Petunias are poisonous to cats and dogs.
You can set this worry aside. The ASPCA lists petunia as non-toxic to cats, dogs, and horses, so a curious nibble will not poison a pet. A big mouthful might bring a brief stomach upset, but that really is the worst of it.
Every petunia needs constant deadheading to keep blooming.
Good news: it truly depends on the type you are growing. Older Grandiflora and Multiflora petunias do rebloom more freely when you pluck away the spent flowers. Modern spreading and Wave types clean themselves and ask for little to no deadheading at all.
Petunias are true annuals that live only one season by nature.
Here is a lovely surprise: by nature they are tender perennials. Gardeners in temperate climates grow them as annuals only because frost is what ends them. Keep the plant somewhere frost-free and it can happily carry on well past a single season.