Mums are a favorite for their vibrant fall blooms. Their successful growth and abundant flowering depend on specific temperature conditions. Mums are sensitive to temperature fluctuations, requiring careful consideration for thriving plants.
Optimal Temperatures for Mums
Mums flourish within distinct temperature ranges for vegetative growth and prolific flowering. During active growth and blooming, optimal daytime temperatures are 60°F to 75°F (15°C to 24°C). This range encourages healthy foliage and flower bud initiation.
Cooler nighttime temperatures, ideally around 60°F (15°C), benefit bud formation and prolong blooming. If temperatures remain too high, especially at night, flowering can be delayed and bloom quality diminished. Conversely, consistently low temperatures can slow growth and affect plant vigor.
Temperature Needs Through the Mums’ Life Cycle
A mum’s temperature requirements evolve through its life stages. For starting from seeds, 70-75°F (21-24°C) is ideal for germination. Cuttings benefit from 50°F (10°C) or above for rooting, with young plants ready for outdoor planting after the last frost.
Once established, newly planted mums thrive in conditions similar to actively growing plants. As mums approach flowering, shortening days and temperature drops trigger blooming. Warmer daytime temperatures encourage initial blooming, but cooler nights, around 60°F (15°C), support sustained flower development and color.
For dormancy and overwintering, temperature guidance varies for in-ground or container plants. In-ground mums in USDA zones 5-9 often survive winter with proper mulching, which insulates their roots. The goal is to prevent repeated freezing and thawing, with dormant temperatures ideally 32°F to 50°F (0°C to 10°C). Potted mums are more vulnerable and should be moved to an unheated garage, shed, or cool basement, where temperatures remain above freezing but cool enough for dormancy, typically 32-55°F (0-13°C).
Protecting Mums from Temperature Extremes
Mums, while resilient, require protection from temperatures significantly outside their optimal range to ensure their survival and continued health. When temperatures drop to freezing or below, frost can damage the plant’s upper parts, causing wilting or discoloration. Covering mums with a frost protection cloth, old sheets, or towels can shield them from temperatures down to 25°F (-4°C). For potted mums, moving them indoors to a garage or shed when a freeze is predicted (32°F or colder) is an effective strategy.
Freezing temperatures, particularly for in-ground plants, can lead to frost heaving, where the plant is lifted from the soil. A 3-4 inch layer of mulch, such as straw or pine needles, insulates the roots and helps maintain a consistent soil temperature, preventing this damage. Container plants are more susceptible to freezing roots due to less insulation, making indoor storage or wrapping pots with insulating material crucial.
On the other end of the spectrum, high temperatures can also stress mums. Temperatures consistently above 85°F (29°C) can delay flowering, reduce bloom size, and cause flower color to fade or revert. Signs of heat stress include wilting and scorched leaves. To mitigate heat, providing partial shade during the hottest parts of the day, especially if temperatures exceed 75°F (24°C) regularly, and ensuring adequate watering are important. Choosing a planting location that offers some afternoon shade can naturally help manage temperature exposure and reduce heat stress.