Chrysanthemums, fondly called mums, are fall’s calling cards. They are easy to grow and are pest and disease resistant so they are as low maintenance as it gets. They work well in pots and in garden beds and come in many different forms with big, lush flowers or daisy-like blooms. In late summer or early fall, you will see them everywhere in nurseries, garden centers and even grocery stores.

They are technically perennials if you get them in the ground in the spring so they can establish their root system before winter. Mums planted in the spring tend to have little trouble surviving. Late August or early September is also a good time to transplant, move or plant mums that allows for good root development prior to the ground freezing. Freezing and thawing of the soil during winter can cause the plant to heave, exposing roots to drying winds, increasing the chance of death.

Sometimes mums do not return in the spring. In this article, we’ll tell you some secrets about mums so they will return each year.
Greenhouse-raised florist mums have been bred and raised for the florist trade. They have been pampered, pinched and pruned into tightly packed balls full of buds ready to burst forth into bloom. However, greenhouse-raised mums will probably not make a repeat performance next year. Most are treated as annuals.
Choosing a “hardy” garden mum or a “field grown” mum and not a florist mum, will ensure their return. The best time to find “hardy” mums is in the spring although some nurseries will have “hardy” mums available in the fall.

Mums like rich soil high in organic matter. Good drainage is essential; a soggy location will cause the roots to rot. If you plant them in the fall, get them in the ground no later than mid-October. The later the mums are planted, the lower the survival rate. A late-planted mum will not develop a good root system in the garden soil.

Dig a hole as wide as the pot and place the plant in the hole so that the crown (where the roots meet the stems) are at ground level — and not any deeper. Backfill the soil, and then water and mulch to retain moisture and control weeds. Mums need full sun which is six or more hours per day. They may adapt to a little shade but they will not bloom well.

Water regularly, especially when first planted. Continue watering until first frost. This is especially important if planting in the fall. The roots are still alive and need water.

Mums need cold to initiate their flower buds so if you planted them in the fall, there is no need to bring them indoors like a houseplant. Delaware’s hardiness zones (7A in the north, 7B in the south) mean that mums can be planted outdoors in the fall and left in place for the winter. Place organic mulch such as wood chips around the base of the plant to protect them from fluctuating temperatures. When the blooms are finished, continue watering until the first hard frost, especially if they are in a pot.

If you are lucky enough to find mums in early spring, pinch off the tips of each branch from late spring to early July. Then the flower buds will form. Pinching after mid-July could delay flowering. Pinching is not as drastic as cutting back the plant. The goal is to encourage bushier growth and help control a mum’s shape and size. This technique gives many more blooms per plant. Mums left to themselves grow tall and leggy and may develop floppy stems later in the season, so pinching at the right times results in the mounded and dense shape we love for these flowering perennials. You can save some of the cuttings to root and propagate new plants. Placed in a glass of water, new roots will be produced in no time. Planted in the fall, mums do not need pinching or cutting back.

As the weather moves to winter and the plants move to dormancy, there is no need to cut them back and cover the entire plant with mulch. Garden mums are versatile plants that can typically survive our winter conditions and require less watering during their dormant period. In the spring, trim off the dead parts. If a mum hasn’t greened up right away in the spring, do not rush to pull out the mum. It may be late spring before you see any action.

Mums will need to be divided every three to four years. They will flower four to eight weeks each year. Mums start to flower based on the length of uninterrupted darkness. Outdoor lights left on overnight can confuse your mums into thinking it is still “vegetative growth” time and they will fail to flower.

Give mums dark nights and bright, sunny days for the best chance of blooming. Happy gardening!

For questions on any gardening topic, call the Master Gardener Helpline: in New Castle County, 302-831-8862; in Kent County, 302-730-4000; in Sussex County, 302-831-3389.
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