Every once in a while, a very good plant shows up in my trial garden, and this time, it’s a mum.

The Igloo series of mums from Blooms of Bressingham comes in a handful of colors, but unlike its fall- blooming cousins, this blooms from July into October or November. This mum is in the Dendranthema plant group, which is related to chrysanthemum.

Chrysanthemum may or may not be a reliably hardy garden mum. Gardeners usually plant them in fall for seasonal color and hope for the best. However, Dendranthema is truly hardy and makes it through winter as smoothly as other perennials in the garden.

I got my first trial plants, ‘Rosy Igloo’ and ‘Warm Igloo,’ three years ago. These are not extremely large because they are planted in part sun. But the ‘Frosty Igloo’ I got this spring is in full sun and has increased its size tenfold. It started blooming a couple of weeks after I planted it and has not stopped.

“Dendranthema is a separate genus and does not have the same habit as mums but looks very similar,” said Christine Kelleher, head of marketing for Blooms of Bressingham North America. “Dendranthema is very promising from the hardiness aspect.”

It also is a plant that does not have to be cut back early in the season like other mums to control its shape and to keep it from splaying.

As do many perennials, this one benefits from an occasional deadheading, more to keep the plant looking tidy than to keep it flowering. The ‘Rosy Igloo’ and ‘Warm Igloo,’ planted in part shade, seem to bloom regardless of how much I neglect them. They are in a spot that I don’t see very often. However, next spring, I will move them to a sunnier, showier spot.

If there’s an issue with this plant, it’s availability. Some retailers can be found at the Blooms of Bressingham Web site, www.bobna.com. I suggest you call your favorite garden center to see if it carries the Igloo series. At www.hoosiergarden er.com, you’ll find mum-care tips.