How to Grow Mammoth Mums

Choose locations that offer at least six hours of full sunlight, good air circulation and well-draining soil. Depending on the desired appearance, adequate space is necessary to accommodate Mammoth mums at full maturity, which takes several years. The University of Minnesota Extension recommends a space allowance of 1 to 2 feet between plants to achieve a solid mass and 3 to 4 feet between plants if you wish to grow other plants between. Several Mammoth varieties attain 5 feet in height and width as early as the second growing season, depending on soil and weather.

Work a 2-to-3-inch layer of equal amounts of compost and coarse sand into the soil at a depth of at least 12 inches. The Purdue University Cooperative Extension Service also recommends adding a balanced fertilizer, such as a 10-10-10 formula, at a rate of 5 pounds for each 100 square feet of planting space. Use a shovel and rake to thoroughly combine the amendments and break up any large clumps of soil.

Dig a hole as big as the depth of the Mammoth mum container so the base of the stem will sit even with the soil line when planted. Repeat this process for each mum to be planted

Grasp each plant at the base of the stem and gently turn it upside down. Lift the container off the root ball and gently loosen the roots to encourage development after planting.

Place the mum in the prepared hole and pack soil into the remaining space, up to the base of the stem. Pat down soil to break up any air pockets.

Water each mum gently to settle it into the soil. Once established, water at least once a week when soil is dry to the touch. The Ohio State University Extension recommends watering during the morning, letting the water to soak into the soil at least 5 to 6 inches. This gives the plants time to dry during the day and prevents any moisture-related diseases.

Apply 2 to 3 inches of mulch around the base of each mum to keep weeds at bay. Check the planting site regularly for weeds and remove them by hand, as soon as they appear, to prevent any disturbance to the shallow root system.

Pinch off the tops of all new shoots, leaving at least two to three leaves on each stem. Purdue University Cooperative Extension Service recommends performing the first pinching when the plants are at least 6 inches tall. Continue the process until the end of July. Discontinue the pinching process when new blooms begin to form.

Apply balanced fertilizer at least once a month, starting in the spring, until blooms begin to form in the summer. Follow the manufacturer's recommended dosage and application methods.

Remove spent blooms during the flowering period to encourage more flower growth. At the end of the season, however, leave spent blooms and stems on the plant in preparation for the cold winter months.

Cover the base of each mum with 3 to 4 inches of mulch to keep the ground uniformly cold during the winter months. Purdue University Cooperative Extension Service recommends mulching in late November or early December, when local temperatures have dropped below 20 degrees Fahrenheit two or three times. This process should be repeated every winter to ensure protection of the plant's base.