Chrysanthemums, so colorful and varied in their form, add vibrant interest to late summer borders and pots. They can be planted throughout the growing season as long as they’re given time, about six weeks, to become established before cold weather sets in. Chrysanthemums, also referred to as mums. are available at garden centers; they’re usually hardy perennials and can overwinter in our gardens. Those sold by florists are often nonhardy varieties and should be treated as annuals.

Mums come in a range of colors from bright yellow to orange and deep burgundy, and shades of pink, magenta, and white. They prefer full sun and fertile, well-drained soils. Before planting, prepare the bed by working well-composted manure or homemade compost into the soil at least 6 inches deep. Fertilizer can also be incorporated to provide additional nutrients.

Water new plants well to settle them in to their new location and apply an organic mulch like shredded bark or wood chips to retain soil moisture and moderate soil temperature. To encourage side shoots and fuller plants, pinch growing tips when the mum plant is about 6 inches tall.

As side shoots develop, continue to pinch growing tips until early to mid-June or the beginning of July, depending on the expected bloom time (early, mid, late summer). Then allow flower buds to develop. Deadhead blooms as they finish to encourage and extend the flowering period. When leaves die back at the end of the season, cut the plant to the ground, remove debris and old mulch, and replenish with fresh mulch. Mounding mulch around the plant will help protect it from frost heaving throughout winter.

Space plants at least 18 inches; mums are susceptible to fungal diseases like powdery mildew, and good air circulation lessens the risk of disease. In the case of powdery mildew or rust, which can affect the leaves, treat by dusting with ground sulfur or other products for this purpose (consult your garden center).

Chrysanthemum stunt and Aster yellows are viruses that can stunt and distort plants. Remove and dispose of affected plants. Don’t place diseased plant material in your compost pile. Keep tools clean and disinfected to prevent transmitting disease.

Chrysanthemums spread by underground shoots called stolons. Every two to three years, in spring after the last killing frost, lift plants and divide them. First, wash much of the soil from roots revealing young plants. Carefully separate these from the old plant and plant in a new location in your garden.

Dispose of the old plant. It’s best not to leave mums in the same location for too many years, especially if older plants suffered from diseases.

Add splashes of color to your late summer garden with easy to grow chrysanthemums!

Submit gardening questions to [email protected] or call 719-520-7684. The in-person help desk is open 9 a.m.-noon and 1-4 p.m. Mondays and Wednesdays at 17 N. Spruce St. Find us on Facebook at Colorado Master Gardeners – El Paso County.