Optimal Temperature for Hydrangeas

Hydrangea shrubs (Hydrangea spp.) produce showy blooms in an array or colors, from pastel pinks to startling baby blues. Soil pH affects their color, making it possible to adjust the soil's acidity according to the color of hydrangea flowers you want. Hydrangeas appreciate moderate climates because both frost and high, withering temperatures cause damage if the plants aren't protected.

Ideal Climates

Different types of hydrangeas typically thrive in different climates within U.S. Department of Agriculture plant hardiness zones 3 through 9. Trying to grow hydrangeas in the extreme zones on the outskirts of this range can prove impossible, whether the damage is frost or sunburn.

Seasonal Temperatures

Hydrangeas appreciate moderate to warm weather in spring and summer, when they're actively growing. Temperatures around 70 degrees Fahrenheit in the day and just below 60 F at night are ideal. During the fall bud development stage, hydrangeas need six weeks of temperatures below 65 F for the buds to set. After this period, the hydrangeas should go dormant in temperatures between 35 and 45 F for six weeks.

Sun and Weather

Hydrangeas are water guzzlers that need moist soil. Though they can thrive in full sun, they need regular watering and protection from the wind to stop the foliage wilting. Hot, dry weather and high winds can accelerate this soil drying and foliage wilting. In hot weather, keeping hydrangeas out of the sun can prevent them from drying out, while extra water can help improve the health of sun-basking hydrangeas when temperatures soar.

Frost Damage

Hydrangeas form flower buds in fall, though they don't blossom until the following year. Plummeting winter temperatures can damage or kill the buds if they're not protected. When spring hits and flowers should bloom, you may notice your damaged hydrangea only has showy green leaves and no blossoms. To prevent this type of frost damage, bring your hydrangea inside if your climate has freezing winter temperatures. Alternatively, cover the hydrangea in burlap on cold nights.

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