If you're looking for a plant that will give you colour all season long, petunias are a great choice. Native to South America, these vibrant blooms may not tolerate frost (which is why they're grown as annuals in the UK), but their flowering period is exceptionally long – giving you vibrant colour well into autumn.
Petunias were first introduced in Europe during the Victorian era and have been a staple in many gardens ever since. Their popularity is hardly a surprise, available in a large variety of colours ranging from brilliant white to hot pink (and everything in between) and delightful patterns, like stripes and speckles.
These pretty trumpet-shaped flowers look beautiful tumbling out of hanging baskets, window boxes, planting beds and containers of all sizes. With a mounding or cascading form, they add bold colour to your garden all season and are popular with pollinators, too.
For the best performance of your petunia plants, there are a few things you should know.
How to care for petunias
Petunias are not super-fussy, but they do need proper care to thrive. If you give them the appropriate light, water and fertiliser, they will bloom for the entire season in most of the country, adding vibrant colour to beds, containers and hanging baskets.
When to plant
Petunia seeds should be planted in the warmth of spring – so they can be sown indoors in April, before being transporting outside. This is mainly because petunias don’t like cold ground, so it's important to wait until after the last frost date. The recommended time to plant petunias outside is typically late spring to early summer, or May to June.
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“Planting at this time allows the roots to establish themselves in warm soil, promoting healthy development,” says Noah Derohanian, Proven Winners director of product management.
Before you plant, it's also worth considering how different types behave. Petunias have a mounding or spreading/trailing form, depending on the variety. Some tend to stay more upright and bushy, while others spread up to several feet wide, so make sure the spot you pick accommodates that.
When to sow
If you're growing petunias from seed, early spring is the time to get started. Sow them inside or under cover in April and harden off before planting them outside in May or June.
Light
Petunias do best when they get at least six hours of direct sunlight per day. “In the shade, petunias will grow, but they will be leggy, reaching for the sun and will not bloom well,” says Steven Engel, regional account manager for Pan American Seed, maker of the Wave Petunia collection.
Soil
Petunias thrive in well-draining soil with neutral to slightly acidic pH, says Steven. Incorporating organic matter and compost into the beds with petunias will help improve the soil structure and increase fertility.
Watering
When watering petunias, pay special attention to the first two weeks after planting, as this stage is critical for their survival, says Noah. Water deeply, letting the root ball become saturated. Then let them dry out slightly between waterings.
If possible, water with drip irrigation or water under the foliage. “If petunias are watered overhead and the flowers get too wet, the blooms will not last as long, and there will be a higher chance of botrytis, which is a disease that causes brown spots on leaves and gray, fuzzy mold on flowers,” Steven warns.
Fertilising
“Feeding petunias is an important factor in keeping them looking good,” Steven urges.
When planting in the ground, use a water-soluble fertiliser in cool temperatures and a balanced 10-10-10 (NPK) slow-release granular fertiliser in warmer temperatures. Follow the label instructions, re-applying according to the directions. In containers, feed with a water-soluble type every 10 to 14 days.
Deadheading
It’s not necessary to deadhead most types of petunias. “The plant will continue to set flowers if it receives proper sunlight and is healthy,” says Steven. The exception, however, is floribunda types, which do better when the spent blooms are removed, which can be done regularly to keep the plants looking neat and tidy.
Common problems
Overwatering
Petunias are relatively low-maintenance plants, but avoid overwatering. If they get too soggy, this can lead to root rot, says Noah. Petunias also can be susceptible to botrytis in wet climates or if overwatered. Allow them to dry out between watering again.
Pests
Aphids, slugs and flea beetles may occasionally affect these plants. Use a blast from the hose to knock down aphids, hand-pick slugs, or use neem oil to manage young flea beetles. The most effective management comes from monitoring and catching problems early.
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Arricca Elin SanSone is a writer, editor, and content creator who specializes in lifestyle and gardening. With a background in health reporting, she applies these same research skills when writing about the science of growing things. She trials new plants in her expansive garden, and her houseplant collection consists of 60+ varieties. Arricca has written thousands of articles for publications such as Country Living, House Beautiful, Good Housekeeping, Prevention, VERANDA, Southern Living, and more. She’s happiest when digging in the dirt, baking, or spending time with the people and dogs she loves.
Charlyne Mattox is the Food and Crafts director with over 20 years recipe development, recipe editing, and crafting experience. Prior to starting at Country Living in 2014, she worked in the crafts department at Martha Stewart Living and Martha Stewart Kids before attending cooking school at the Institute of Culinary Education in New York City. She was nominated for a James Beard media award while a senior editor at Real Simple magazine and authored a cookbook Cooking with Seeds.
When not in the kitchen she loves to garden, focusing on growing flowers and kitchen herbs (of course), watering her 25 house plants, and knitting scarfs or hats she will never be able to wear in the always hot and steamy Alabama.
