Q: I have three potted mums on my porch. The flowers are fading, and I am wondering what to do with them next. They were expensive, and I would like to keep them until next year. I have a place in the back of my vegetable garden where I could bury the pots until next spring. What do I do with them in the spring?
A: Some potted mums are not hardy and won’t make it until spring no matter what you do with them. Some are what we would call garden mums, and they can grow in hardiness zones 4 through 9. A key to keeping garden mums alive over the winter is keeping the soil damp. They are in a lightweight potting soil mix. If there is no rain or snowfall, they will need to be watered. It will be easier to keep the soil damp if they are planted out of their pots until spring, even if you want to grow them in pots over the summer. The surrounding soil will help keep the roots moist, whereas a plastic pot would block the flow of water to the roots.
Dig a hole big enough to plant them, pot or no pot. The dead top can be cut off or left on if it will help accumulate snow for insulation. Either way, cover the soil around and over the crown 3-4 inches deep in mulch.
They are not the fastest growers in the spring, so they may look dead as other plants start growing. Give them time. You can repot them while they are still dormant if you are not going to leave them in the ground. Cut off the dead top if you didn’t already do that. If you decide to dig them up, you can use a sharp knife to cut the roots, crown, and soil ball in half or quarters to get more plants.
They grow best in full sun of six to eight hours a day. In hot climates, they like afternoon shade. Since they depend on the day length growing shorter in the fall to begin setting flower buds, don’t plant them where landscape lighting will “keep them awake” at night.
The soil should have lots of organic matter and good drainage. Again, don’t let them dry out. The roots can survive cold soil temperatures in the winter of around 0 degrees Fahrenheit. In the summer, mums can survive 100 degrees if given plenty of water. Fertilize them with a flowering plant fertilizer according to directions.
To get a fuller plant with more flowers, the mums should be pruned every time the new growth reaches 6 inches long. Cut each 6-inch long branch in half. Stop pruning them in mid-July to allow flower buds to form. They may only need two prunings, so it is not too much work.
If you don’t want to plant them over the winter, you can bury the pots deep in a pile of leaves. Shredded leaves work best. Bury them a foot or two deep, and cover the leaves with wire mesh to keep them from blowing away.
Even though they make great potted plants and provide fall color after most other perennials have stopped flowering, garden mums are not the greatest perennial plants. After a few years, they might just die. Or they might need to be divided, because they spread out from the center, creating a ring of mum plants with a dead spot in the middle.
Since you already have the plants and a place to store them over the winter, I think you should give them a try.
