Mum flowers (Chrysanthemums), herbaceous perennials valued for their large flowers, bloom during fall, adding a splash of color after most annuals have died back. The flowers appear in any color except blue, depending on the variety. The hardy plants reach up to 3 feet tall, though any size can be maintained with regular pruning. Hardy in zones 4 through 11, mum flowers thrive throughout much of the U.S., but require special winter care to survive in cool climates.
Plant mum flowers during spring after all danger of frost has passed. Choose a planting site that receives full sunlight throughout the day and consists of well-drained soil. Apply a 3-inch layer of organic compost to the planting site and use a spade to work it into the soil to improve fertility and drainage before planting.
Spread a 2- to 3-inch layer of mulch over the soil surrounding mum flowers to deter weeds and improve moisture conservation. Begin the layer 2 to 3 inches from the plant's crown to minimize the risk of disease caused by inadequate air circulation.
Water mum flowers once per week during spring and summer to keep the soil moist at all times but not wet. Soak the soil to a depth of 4 to 6 inches at each watering to ensure the plant receives enough moisture. Do not water during fall or winter.
Feed mums once per year during spring using a slow-release 5-10-10 NPK fertilizer to slowly add nutrients to the soil throughout the year. Read the manufacturer's directions for proper application and dosage information.
Pinch back mum flower side branches by 2 to 3 inches when they have reached 6 inches in length to promote bushy, compact growth. Continue pinching regularly until mid-summer to ensure flowering before winter.
Spread a 4- to 6-inch layer of mulch over mum flowers during late fall to insulate the soil and protect the roots against cold damage during winter. Remove the mulch and reapply the previous 2- to 3-inch layer the following spring after all danger of frost has passed to allow new growth.