If you’re new to flower gardening or just want plants that are relatively carefree and abundantly beautiful, you can’t go wrong with learning petunia care.
These fragrant flowers are easy to grow from seed, cuttings or when purchased as nursery seedlings. In this article, we will look at the how-to of planting petunias, growing petunias and, introduce some of the more popular petunia varieties.
How To Care For Petunias
Family: Solanaceae (Sol-an-nay-see-ee)
Origin: South America
Genus: Petunia (Pet-tew-nee-uh)
Species: Hybrida (hib-rid-uh)
Height: 12 inches to 18” inches
USDA Hardiness Zones: Selected varieties grow from USDA Hardiness zone 9 – 11
Flowers: Single and double flowers 1 to 3” inches in diameter. Colors from purple, white, pink, and even black, with a width array in between.
Foliage: Deep to pale green leaves with a hairy and sticky texture.
Petunia Plant Care Requirements: Sow seeds 6 – 10 weeks before last frost. Do not allow plants to become pot bound. Cut back plants to retain growth, shape and encourage branching. Remove spent petunia flowers to produce more flowers and keep plant from going to seed. Outdoors bright light to full sun. Water thoroughly. Plants need good well-drained soil inside or outside. Do not allow plants to sit in water. Responds well to liquid feeding.
For continuous bloom, remove faded flowers and keep plants from going to seed. Prune plants to prevent straggly growth.
How To Grow Petunias: Over 100 Types
These happy little plants started with petunia x hybrida and hybridized to produce large, blowsy blossoms, beautiful flowers, frilly double blooms, and more in an astonishing variety of colors and patterns.
Growth habits range from compact, perky, and upright to rampant traveling, cascading, and trailing petunias.
Whether you want to fill containers or grow petunias in hanging baskets, border your walkway or cover a large area of ground, there’s a petunia to suit your needs.
All petunia varieties make excellent containers, window-box, and potted plants, but double-flowering varieties are uniquely suited for this use because of their abundant and luxurious blossoms.
“Wave petunias” which debuted in 1995 are an excellent choice as a ground cover.
They spread abundantly and attract valuable pollinators such as bees, butterflies and even moths in the evening. Planting petunias near a window or at the perimeter of your patio to enjoy a nighttime showing of interesting moths.
Seek outspreading and trailing petunias for use in baskets. These fast-growing petunias overflow their baskets rapidly and beautifully fill your porch, patio or sunroom setting with color and fragrance.
4 Groups of True Petunias
True petunias are annuals or “tender perennials.” They make up four categories, each consisting of wide-ranging choices in coloration.
#1 – Grandiflora Petunias
The Grandiflora types are specimens with large, showy flowers. These plants damage easily by rain, so it is a good idea to plant them in baskets or containers placed in sheltered areas.
#2 – Multiflora Petunias
The Multiflora types are not as susceptible to rain damage. These plants produce smaller blossoms than Grandiflora but produce many more flowers. They make an excellent choice for flowerbeds and other less-protected settings.
#3 – Milliflora Petunias
The Milliflora types are very small petunias. They produce enormous quantities of tiny (1″ inch across) pretty flowers. They can be planted relatively close together (6″ inches) and make great border plants and potted plants.
#4 – Spreading Petunias
The spreading petunias make an excellent ground cover. They do not grow very tall, but they do spread very quickly with proper feeding and watering. They are lovely spilling over retaining walls, rambling down hillsides or overflowing window boxes or hanging baskets. [source]
Most Popular Petunia Choices
Top recommendations from the Farmer’s Almanac for the best petunias to plant include:
Rose Star is one of the spreading petunias that presents a striped appearance thanks to rose-colored flowers featuring a white center.
Carpet Series – a compact, mound-forming variety that makes an excellent edging plant or potted plant. This cultivar is available in many colors.
Sugar Daddy – a fairly durable Grandiflora producing big, showy dark purple flowers ornamented with dark veins. Unlike many of its brethren, the blossoms of this plant do stand up well to rain, so it can be planted in a wider variety of settings.
Other popular recommendations include:
- Surprise Lime bears large, white flowers with yellow centers. It is a wonderful choice for a moon garden as the blossoms look very much like Moon Flowers and are very attractive to Hummingbird Moths.
- Potunia Plus Red is an excellent choice if you want to attract hummingbirds and other beneficial pollinators. This Grandiflora features big, bold, red flowers that stay bright and vibrant even in hot, dry weather.
- Suncatcher Pink Lemonade is a pretty, trailing early bloomer in shades of mingled pink and yellow.
- Limelight presents a striking magenta coloration with lime-tinted edges. This compact plant is an excellent choice for a border.
- Prism Sunshine’s flowers are deep yellow in the center with creamy yellow edges.
- Sweetunia White Merlot produces masses of tidy lavender/rose blossoms with deep magenta centers. The plants are compact and present a neat, rounded shape that looks great in a hanging basket or container.
- Mini Rose Blast Pink has rosy blossoms with splashes of magenta. This is a compact plant that tends to stand erect. It does not trail. It’s a nice choice as a bedding or border plant.
- Purple Pirouette is a double flowering variety in deep purple with frilly white edging. It’s a strikingly beautiful plant, and caterpillars seem to think so too. Using Bacillus thuringiensis (Bt) preventatively is a good idea with this variety. (More on this in the “caterpillars” section!)
- Cascadias Rim Magenta has deep purple flowers with striking white edging. This is a trailing plant that does well hanging in baskets.
- Wave Blue features masses of electric blue flowers and very little foliage. It’s a beautiful choice for a focal point such as a window box.
- Fortunia Early Blue Vein these early bloomers present silvery-white petals with a deep purple center.
Are Calibrachoa And Mexican Petunias True Petunias?
Calibrachoa – Million Bells
Calibrachoa (Million Bells) and Petunia are both in the Solanaceae family along with the nightshade and tomatoes. Since Calibrachoa looks like tiny petunias it was considered to be part the Petunia genus.
After the study of DNA markers, a published report in 2005 showed the measured fingerprint the species shared.
It was suggested that Calibrachoa was a separate genus and group from Petunia. [source]
Mexican Petunias – Ruellia Simplex
The Mexican “Petunia” is not a petunia at all. This hardy perennial (sometimes invasive) plant is also known as Britton’s petunia and Mexican bluebell. It also has a bevy of scientific names, but it is most commonly referred to as Ruellia simplex.
It’s an attractive plant that comes in a variety of colors. The most common is purple, but Mexican petunia can also be found in shades of white and pink.
This adaptable plant grows in the wild in Mexico and South America, as well as the Antilles. It was brought to Florida in the mid-20th Century and quickly naturalized and traveled to other states. It has also been naturalized in the Virgin Islands, Puerto Rico and Hawaii.
The plant thrives in all manner of conditions ranging from woodland to pasture land and wetland to desert. In many areas, it is considered invasive, so check with your local agricultural extension before planting to see if it is permitted in your area. [source]
9 Steps On Growing Petunias – How to Care for A Petunia
#1 – Petunias Sun Or Shade
When planting Petunias start by choosing your setting carefully. Petunias enjoy bright, direct, full sun – except in areas with very harsh, hot, punishing sun exposure.
In desert settings or very hot areas, bright, indirect light is appreciated. All types of petunias should be protected from strong winds.
#2 – Planting Medium
Like most plants, petunias need light, well-drained soil. Sandy soil with a slightly acidic pH level (6.0-7.0) works well. When planting petunias in flowerbeds outdoors, prepare the soil by tilling to a depth of 6″-8″ inches.
Turn in some finished organic compost (e.g. manure, well-rotted leaf compost, or baled peat moss) to help aerate the soil and add natural fertility. Use a soilless potting medium when planting petunias in pots, planters, or containers.
#3 – Space
Be careful not to overcrowd. Once you have your flower bed prepared, dig evenly spaced holes that are just about the same size as the pots your seedlings currently occupy.
It’s a good idea to establish your plants in groupings of three or more. If you have a narrow space to plant, be sure to leave 8″-10″ inches between plants in rows for Grandiflora and Multiflora varieties.
All varieties of these plants grow enthusiastically, so start out with sparse planting. Note that small Milliflora varieties can be planted as close as 6″ inches apart; however, ground cover varieties need about 18″ inches of space between them. [source]
If you are transplanting to a container, the general rule of thumb is to plant three seedlings in a standard ten-inch pot or basket. If you are planting in a planter or window box, allow approximately ten inches of space between plants.
#4 – Careful Planting
Remove the seedlings from their containers. If they seem root-bound, massage the roots a bit to loosen them up. Place each little plant in its prepared hole and fill in around it with fertile, sandy soil. Firm it down to give your seedlings some support.
#5 – Nutrition
When transplanting seedlings, give each little plant a teaspoonful of balanced, slow-acting, all-purpose granular fertilizer. Sprinkle it lightly over the soil around each plant to provide basic, consistent nutrition. Water well, and keep the soil uniformly moist (not soggy) until your plants have become established.
Producing big bundles of gorgeous flowers takes a lot of energy. Mature growing petunias are heavy feeders and need ongoing feeding during their lengthy blooming season. You can expect to feed them from late in the springtime to mid-autumn.
Use a slow-release fertilizer to provide steady, consistent nutrition. Apply liquid water-soluble plant fertilizer once a month to most types of petunias. Those that produce double-flowers should be fertilized twice a month with liquid fertilizer.
#6 – How Often To Water Petunias?
Like wildflowers, when planting petunias in flowerbeds they appreciate a deep, weekly watering. Soil should be damp to a depth of six or eight inches after watering.
Remember that plants in containers and pots need more frequent watering than those planted in the ground. This is especially true of clay pots. When growing petunias in containers, check plants often to determine watering needs. It is not unusual to water container petunias once or even twice daily during hot, dry weather.
#7 – Mulching
A good layer of mulch surrounding your petunia plants will help protect the roots. This will help keep the soil at an even temperature and conserve water. Organic mulch also suppresses weeds and decomposes steadily to provide nourishment to your plants.
Some good choices in natural mulch include:
- Wood chips
- Shredded bark
- Chopped leaves
- Dried grass clippings
Petunia roots are fairly shallow and tend to dry out rapidly. Good soil with plenty of organic matter will hold moisture longer. Mulching around your plants will also help retain moisture.
#8 – How To Prune Petunias
When your seedlings have reached a height of six inches, pinch their central stems back. This will make them bushier by forcing the development of side stems.
In the middle of summer you may notice your mature plants getting leggy and spindly. When this happens, flower production will falter.
Revitalize your plants by cutting them back to half size. Within a couple of weeks, they will have generated new growth and will begin to flower anew.
#9 – Deadhead
To encourage more blossoms, regularly pinch off entire dead flower heads, including the portion supporting the blossom. This will prevent your plant from going to seed.
With this type of complete deadheading, you can keep your plant alive and blooming all year round if you bring it indoors and keep it as a houseplant during the winter.
If you want the plant to set seeds, simply pull the soft petals gently from the plant leaving the seed pod in place. The pod will mature and produce seeds that you can gather or allow to scatter freely in your flowerbed for self-seeding in the coming year.
How To Propagate Petunias?
Petunias are astonishingly easy to propagate from seed or cuttings. You can also purchase them by the flat very affordably online, through mail order or at your local garden center. A wide variety of choices including spreading petunias are available every spring.
These plants are considered “tender perennials” in that they are only cold hardy in zones 9-11. In other zones, they are typically planted as annuals; however, under the right conditions, they will re-seed themselves to return to your garden setting year-after-year.
How To Grow Petunias From Seed
If you plan to grow petunias from seed, you should know that these seeds take quite a while to germinate. Get an early start, sow seed by planting petunias indoors late in the winter or very early spring. You’ll need:
- A small amount of sand
- Peat pots or two-inch deep flat boxes
- Seed starter mix or a soil-less medium such as coco coir
Between six and ten weeks before the last anticipated frost, fill your containers with your starting medium. Mix your petunia seeds with sand. Sow seed by sprinkling the seed/sand mixture over the starting medium. Don’t cover with soil or coco coir because the seeds need exposure to light to germinate.
Set your trays or peat pots into a shallow container to soak up water from below. You can lightly mist the surface of the potting mix to dampen the seeds and help them settle into the soil.
DO NOT pour water over the soil as this will displace the tiny seeds and may cause them to cluster together in one area. You want to maintain a bit of distance between them.
Keep the soil lightly and uniformly moist as your seeds germinate and grow into seedlings.
Cover your pots or trays loosely with plastic wrap or a plastic cover to help keep humidity high. Place the containers in a warm area with bright, indirect light. You should see results within one or two weeks at standard household temperatures (65°-75° degrees Fahrenheit).
TIP: Petunia seeds are extremely small, that’s why mixing them with sand is a good idea.
You may see petunia seed pellets advertised, and this may seem like a good way to make it easier to keep track of them; however, this product receives roundly negative reviews from consumers. It may be that incorporating these tiny seeds in pellets interferes with light exposure.
Root Cuttings in Potting Medium or Water
You can also start petunias from cuttings for an endless supply of fresh plants. They can be rooted in loose, well-drained soil, compost and/or coco coir, or you can even root them in water. This is an excellent way to make use of the trimmings when pruning leggy petunias or when using petunias as cut flowers.
- Always take your cuttings from healthy plants.
- Ideal cuttings are 4-6 inches long.
- Remove leaves from the bottom 2 inches of the stem.
- Remove blossoms (unless you want to keep your cuttings as cut flowers!)
- Rooting hormone is helpful but not necessary.
- To avoid rotting in cuttings started in potting medium do not overwater.
- To avoid rotting in cuttings started in water, change the water every couple of days.
The steps required to root cuttings in planting medium are very much like those for starting seeds. If you want to start cuttings in water, simply place them in a jar or vase of clean water in a warm area with bright, indirect light. In either case, roots should develop within a couple of weeks.
This video discusses rooting petunias in planting medium as well as rooting in water and starting from seed. This presenter has better luck with the water method. Additionally, the video clearly demonstrates just how rampant and eager to thrive petunias really are!
4 Tips For Growing Petunias In Hanging Baskets
If you take proper care of your petunias, you can expect them to provide bright spots of color and abundant blossoms in springtime, throughout the summer and well into the fall.
Below are some smart tips to help you get the best blossoming performance from your hanging basket petunias.
#1 – Don’t Neglect Plants In Hanging Baskets
By their nature hanging baskets are very exposed to air and are subject to drying out. Additionally, they have very limited growing medium to provide nutrition, so they need regular feedings and watering. In hot, dry weather hanging baskets may need watering once or twice daily.
#2 – Choose The Right Location
Even though petunias like full sun, don’t subject them to blistering direct sun in extremely hot climates. They will gladly welcome some partial shade.
Bright, slightly indirect light is better. Remember to shelter hanging baskets from excessive wind to avoid drying out and damage.
#3 – Water Completely and Thoroughly
When watering hanging baskets, allow the water to run through the plant freely. Once weekly, add a balanced (5-10-5) water-soluble liquid fertilizer to promote blooming and new foliage growth.
#4 – Deadhead Regularly
Deadhead blossoms and trim or pinch petunias back regularly to promote new blooms and avoid a leggy appearance. [source]
6 Ways to Keep Petunias In Containers From Getting Leggy and Scraggly
#1 – Start by selecting varieties known for hardiness and long-blooming qualities. Among these are the Wave Petunia series, which feature masses of pretty blooms and a quick-spreading growth habit. Look for:
- Misty Lilac Wave
- Purple Wave
- Rose Wave
- Pink Wave
These are excellent choices to fill window boxes, hanging baskets and containers with hardy, long-lasting, abundant blossoms. Wave series petunias need little or no deadheading or pinching off for vigorous growth and performance throughout the spring, summer and early autumn.
#2 – With other varieties of petunias, after the first flush of blooms, you may find that your petunias begin to look scraggly, worn out and stop blooming.
To tidy them up, encourage new growth and promote new blooms, just pinch or prune them back to a height of about four inches. You’ll have a whole new set of fresh blooms and bright foliage in just a couple of weeks.
Petunias provide a lot of color. They can be stunning plants with a little work. Here is an instructional video (about 7:30 minutes) on keeping your Petunias lush and Flowering…
A piece of advice… the video is a little long so skip ahead! If you can get past the Ahhhha’s there is some good info! Enjoy!
#3 – Avoid having blossoms look battered, take care to keep them dry. Water deeply, once a week or so with a soaker hose rather than a sprinkler or sprayer.
#4 – Early in the summer and toward the middle of the growing season, give your plants a feeding that is higher in phosphorous and lower in nitrogen.
#5 – Use companion planting wisely. Understand that petunias are susceptible to viruses commonly carried by some other plants. For example, some cucumber plants carry cucumber mosaic virus.
Aphids can transmit this virus from cucumbers to petunias. For this reason, you must plant disease-resistant cucumbers and take steps to prevent and get rid of any aphid infestation.
#6 – Don’t let anyone smoke or otherwise use tobacco products in the garden because tobacco users can spread tobacco mosaic virus to petunias. If this happens, your petunias’ leaves will turn yellowish/green and will become twisted and deformed.
The blossoms will also become deformed. All smokers should wash hands and/or wear latex gloves to handle petunias. [source]
Common Petunia Pests
Deer and Rabbits
To prevent having deer and rabbits eat your petunias, fence them off and/or plant them in hanging baskets out of reach. You may also wish to try various deer repellents on the market. Keep your yard clear of brush piles to prevent having rabbits set up housekeeping.
Bobbex Deer Repellent | Ready-To-Use Deer Deterrent Spray Price: $13.33 Keeping a dog will discourage deer and rabbits from approaching your home and garden. Providing a deer and rabbit feeding station away from your plants may also help redirect them. Set up an area far-removed from your house and garden to leave fruit and veggie scraps, deer corn and water for deer and rabbits.
The caterpillars of both pests and desirable butterflies enjoy eating petunia leaves. If you see a thundering herd of caterpillars eating on your plants, you can be reasonably sure they are undesirable (e.g., Yellow Wooly-Bear and Tomato Hornworms).
In this case, pick them off and drop them into a bucket of water laced with dish soap. Pinch off the parts of the plant that have been damaged and give your petunias a good watering and feeding.
Caterpillars with solitary habits are usually baby butterflies. If you see a few of these, it is better to simply share your plants with them or set up a butterfly garden so that you can relocate any butterfly caterpillars if they appear in areas where you don’t want them.
If bunches of caterpillars have infested a large area, you may wish to use Bacillus thuringiensis (Bt) to address them.
This is a natural bacterium that targets caterpillars (good ones and bad ones). Dust it over your plants and the caterpillars will ingest it as they feed. For best results, use it early in the infestation while the caterpillars are still very small.
If you notice your petunias having yellow, puckered leaves they may be infested with aphids. These tiny insects are soft and squishy with green or reddish pear-shaped bodies.
You will find masses of them on the stems and undersides of your plants’ leaves where they congregate to suck the juices out of tender, young plants. They may also attack mature plants, but they are more attracted to soft seedlings.
This is another tiny insect that can cause lots of damage to petunias. Like aphids, thrips are very small and appear en masse. They have piercing, sucking mouth parts which they use to consume the mesophyll and the epidermal cells of both the flowers and the leaves of plants. When this happens, you will see silvery scars on the plant leaves. The insects also lay eggs in the tissues of the plants, causing further damage. [source]
Natural Insect Management Helps Prevent Viruses
Aphids and other insects can transmit incurable viruses to your plants. It is important to keep harmful insects under control to prevent the spread of these viruses. One way of doing this is to introduce and encourage birds and true bug eating beneficial insects such as:
… and others that will naturally reduce the detrimental insect population.
Common Petunia Disease and Ailments
#1 – Black Root Rot
Black Root Rot causes stunted root growth. To avoid this condition, be sure to use light, well-drained soil and do not allow petunias to stand in water.
#2 – Botrytis Blight
This Botrytis disease is a fungus that takes up residence in injured, dead or dying plants. It is more likely to occur in a humid, low-light environment.
Symptoms of infection include translucent spots on blossoms, leaf blight and fuzzy, moldy spots on withered stems. Take quick steps to remove and destroy all infected plants and remedy any problems causing dank, humid, dark conditions.
#3 – Damping-off
To avoid infestation by these organisms, be sure to plant petunia seeds on the surface of a well-drained, sterile sprouting medium. Provide ample light and warmth and just the right amount of water.
Keep pH levels slightly acidic (5.5-6.0) to discourage fungal growth. Always sterilize pots and equipment before use.
#4 – Impatiens Necrotic Spot
Impatiens Necrotic Spot is a viral disease which usually manifests on foliage as brown, yellow or white spots that may have a brown border. Occasionally, the spots may be mottled.
The virus is spread by thrips, so clearly, insect control is vital in preventing this problem. If plants become infected, the best control is to destroy the plants by burning them. Even if the plants recover, they will continue to carry the virus and infect other plants. [source]
#5 – Shoot Proliferation and Leafy Gall
Shoot Proliferation and Leafy Gall is caused by the bacterium, Rhodococcus fascians. The disease is spread through infected water and by taking cuttings from infected plants.
Symptoms of infection to watch for include stunted growth, reduced flowering and leafy galls (clusters of stunted stems).
To avoid infection, be sure to only take cuttings from healthy plants. Always sterilize all equipment after each use. Keep a tidy work area and always remove and destroy any diseased plants.
#6 – Petunia Stem Rot
Petunia Stem Rot is caused by a soil-borne fungus (Sclerotinia sclerotiorum) that can live in dead plant matter for years.
The disease thrives in cool, wet conditions and is very likely to affect plants that grow thickly and do not have adequate air circulation. Affected plants develop lesions at the base accompanied by white, cottony mold growth. Hard, black, spore-containing lumps may also be present.
The plant’s lower leaves will die, and the upper portions of the plant will soon follow suit. To avoid this problem, practice good housekeeping. Keep pots and equipment clean.
Prune plants to remove dead growth and promote good air circulation. Don’t allow plants to become waterlogged, and dispose of infected plants right away.
#7 – Petunia Viruses
Petunia Viruses include:
- Beet curly top virus
- Tobacco mosaic virus
- Cucumber mosaic virus
These are spread by insect infestation and by use of infected equipment. These viruses can also be spread via contaminated hands or contaminated surfaces.
Stunted growth, mottled, discolored foliage and deformed leaves and blossoms mark the presence of these viruses.
To avoid infection and spread, new plants should be quarantined before being introduced to the garden or greenhouse. Hands, tools, surfaces, and equipment must be kept clean. Infected plants must be removed and destroyed. [source]
Good Garden Management Helps Prevent Disease
Remember these tips to help your plants stay healthy!
- Be sure to provide your plants proper watering and nourishment to help them ward off illness.
- Take care to sterilize your garden tools between uses so that you do not accidentally spread viruses through your plantings.
- Avoid exposing your petunias to tobacco products.
- If your plants do become infected, show no mercy! Dig them up and burn them or put them in a sealed trash bag and toss them. You will not be able to save them, and you don’t want them to infect other plants.
Grow Petunias: A Flower for all Reasons!
It’s easy to see why petunias are such a popular flowering annual. With such tremendous variety and such a long blooming season, these lovely, fragrant plants have little trouble finding a happy place in any yard, garden or home.
Choose low-growing varieties as flowerbed border plants, or plant petunias in containers on your porch, at your doorway or around your patio or pool. If you find yourself overwhelmed by masses of petunias, they even make lovely cut flowers to brighten your home.