Time to Water? Here’s the Word on Mums

For years experts have insisted there is no safe way to tell how often a houseplant needs watering. Their advice to “water when dry” was accurate enough but unfortunately left many folks struggling for clues and wondering why a fixed schedule wasn’t possible.

Now there is, at least for potted, flowering chrysanthemums.

Yoder Brothers of Barberton, Ohio, says its research shows that it is better to water a potted, flowering mum every other day than run the risk of it wilting.

The change was included in Yoder’s recommendations for caring for potted mums received as Easter or Mother’s Day gifts. (The chrysanthemum, a popular spring gift, means “golden flower” in Greek, and yellow remains the top-selling color.) But the techniques will be as effective year-round.

“Consumers who follow the commonly used instructions to water when dry are more likely to let their plants wilt than those who water every other day,” says Edward A. Higgins, Yoder’s expert on mums. “Every time a pot mum wilts, flower life is reduced by at least one day.”

His suggestion applies only to flowering mums, not all houseplants. And there are cautionary flags: Water from the top until water runs out of the bottom of the pot; don’t allow the mum to stand in water for more than a few hours, and be sure to remove decorative outside covers and drain excess water.

Place the new mum in a sunny location where it will receive at least half a day of bright, indirect light. But avoid direct afternoon sun, which can burn the flowers, Higgins advises.

Avoid placing it on appliances that give off heat, such as television sets or the fridge, or near heater vents or drafts.

Generally, if the room’s temperature is comfortable for you, it will be good for the potted mum too. Longest flower life is likely at 60 to 65 degrees.

Locally, pot mums can be planted outside and may flower in October or November in areas not touched by hard frost, but most people are better off trying to reflower a potted mum indoors, Higgins says.

He starts by cutting back the stems halfway to one-third once all the flowers have faded. The challenge is to see how close you can come to matching the original flowers produced by a professional grower.

If necessary, repot the mum from, say, a 4-inch pot to a 6-inch pot. Commercial potting mix simplifies this.

To grow plants in a sunny window or outdoors on a patio, Higgins recommends pinching new growth in half whenever it is 4 to 5 inches tall. This needs to be done at least twice.

In nature, mums grow leaves and stems when daylight hours are long in spring and summer and begin to set buds and flower with the coming of fall and shorter days. So artificial darkness will be required.

Higgins suggests covering the plants with a cardboard box or putting them in a closet for 12 hours each night after the last pinching. Temperatures in the dark should range from 60 to 72 degrees. Higher ones make the plants too tall and weak; cooler ones are likely to retard flower development.

During the day, keep the plants in a sunny location. Higgins says they will be in full flower eight to 10 weeks after the start of the darkness routine.

In theory, mums can be forced to flower on any target date. In the 1930s, researchers discovered they could be made to flower 52 weeks a year by regulating the light they received.

Varieties flower in nature at different times, of course. In general, the earliest are the garden types that flower normally outdoors in September or October; the latest are the types grown for sale in pots.

Good drainage is a must. They dislike wet feet.