The Temperature Range for Petunias

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Garden petunias (​Petunia​ x ​hybrida​) are popular bedding plants with showy and colorful flowers. Depending on your climate, they can bring constant color to garden spaces or containers year-round. Petunias like warmth and grow as perennials in U.S. Department of Agriculture plant hardiness zones 10 and 11. However, don't despair if your area's climate is cooler, because you can grow them as annuals.

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Petunia Notable Characteristics

Other than their obvious characteristic of nonstop color starting in spring and until your region's first frost, petunias are low-maintenance plants and the perfect selection for those who want all the beauty without putting in much work. The cheery funnel-shaped blooms cover the plants, accenting the sticky green leaves. Flower colors are solid or speckled and are found in a wide range of hues. Depending on the variety, plants can have a more upright or spreading growth habit. Petunias can grow anywhere from 9 inches to 18 inches tall and spread from 1 to 3 feet.

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Although there are hundreds of different types of petunias, plants are categorized by their habit of growth and bloom size. Spreading varieties produce long stems with a fast growth rate. Milliflora types produce the smallest flowers and plants. Multiflora varieties produce the greatest amounts of flowers that are slightly smaller than grandifloras. Grandiflora types produce the largest blooms. Regardless of type, the blooms attract butterflies and hummingbirds.

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Petunia Preferred Temperatures

Only those living in frost-free climates that are consistently warm can grow garden petunias as short-lived perennials. However, those in cooler locales should treat them as annuals or grow them in containers and protect them during winter. They will continue bringing color to the garden until the first frost.

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Petunias thrive in temperatures of 40 to 90 degrees Fahrenheit, making them hardy and colorful additions to a landscape or hardscape during the warm months of spring through summer. When many plants die as the thermostat starts rising toward 90 F, petunias don't miss a beat. However, the color of the flowers is more intense when temperatures are at the lower to middle range of their tolerance. They're sure to bring a cheery appeal to borders, mixed beds, containers and hanging baskets and also work well in butterfly and pollinator gardens.

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Those growing their petunias in containers who also experience cold winters should bring the container into a protected location before temperatures get too cold. If a frost is on the horizon, bring the container indoors and situate it in a warm location that gets bright light.

Petunia Growing Conditions

Growing petunias in their preferred conditions results in healthy growth and the optimal production of blooms. It's best to wait until the temperature of the soil reaches 60 F before you plant your transplants in the garden. Select a weed-free area sited in full to partial sun. Although plants tolerate a wide range of well-draining soils, fertile soils with good drainage produce the best growth.

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If you're growing petunias in a container, make sure to select one with bottom drainage to prevent rot problems. Use a fertile potting mix that drains well. Potting soils can sometimes be too heavy and remain wet for too long due to improper drainage.

If plants start losing their vigor in summer, prune back stems to promote new growth. Always use clean pruning tool blades when making cuts so you don't accidentally transfer an unwanted disease to your petunias. Water regularly to keep the soil evenly moist, especially if outdoor conditions are hot and dry. Check the soil in containers and, if the top inch is dry, water until it runs from the pot's bottom.

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