One of the keys to getting a truly hardy Mum established so that it over-winters, is to plant early, i.e. May or June.

If you want a nice Mum look for the Minnesota series this spring (MinnRuby, Lemonsota, etc...). If you're in the area, the Flower Factory in Stoughton has all of them. My mums are all up already so it sounds like you lost those.

I'm fairly certain the Mammoth series came from the same University of Minnesota breeding program. They were previously marketed as the "My Favorite" Mums.

How can I tell if they are cashed out? Just the fact that no growth has shown?

By now, that's a pretty good sign. ;)

In most areas, the season is actually ahead of schedule.

For more info on the breeding at the U. of Minn, check out link below.

Here is a link that might be useful: U. of Minn Mum breeding

Thanks for the link. I didn't realize the Mammoth ones were also from U. Minn.

what cool said ...

plus.. there is a good chance that it was hyper-fertilized.. and if you did not remove enough of the potting media... it may have gone into freeze actively growing ... or the high peat base media too wet.. and the roots just rotted out ...

mine are barely peeking out now.. 3 died.. and one lived ...

the best way to accumulate mums.. is to beg pieces off of local garden friends.. who have had them for years..

there used to be a mail order house.. only mum cuttings.. i ordered 30 different kinds [a buck a piece]... after 2 years.. i had about 8 left.. not all mums are hardy everywhere .... and many of the ones sold at bigboxstore are basically shipped as annuals .... i am sure they are perennial somewhere.. just like its 5 oclock somewhere.. lol.. but not in my zone ...

ken

This really ticks me off because the Mammoth Mums are supposed to be hardy to zone 4. This was an extremely mild winter with I believe a low of -2...vs a typically low of -16 or so.

I had plans to split them this spring too!

With this said this is why the nursery said it would be plenty fine to plant at the time I did.

No way in heck I'd pay $10 for an annual...annuals in my opinion are the dumbest thing, unless we are talking containers.

I planted 6 geraniums at the same time and they all came back! They are a full zone less hardy than the mum.

Unfortunately mums are much more sensitive to when they are planted than geraniums. As everyone before has said plant them in spring/early summer. Fall planting has very low survival rate.

My Mammoth survived a winter with -30. This year I had good snow cover, but that's not always the case. As others said plant them in the spring, do NOT cut back the stems in the fall and they MUST have good drainage.

Nursery agreed to give me replacements. They are the ones that said it was perfectly fine to plant them in early September...sounds quite clear they should be planted in spring.

The funny thing is they said wait until the end of May to say for sure if they're dead...ok my Clethra, Oak, rose of sharon and Ginkgo have just about leafed out...they are dead, lol.

You'll sure know when you dig it up. The roots should be healthy. I grow/have grown garden mums for years in my business. Many grown and sold in retail lots are forced too hard and grown too soft, put on drip emitters so they get watered when they might not need it and are dead men walking. When they're in full glory and still in their pot..........they don't take to transplanting well. Like said.......get them in the spring if you can find them.

And when you plant mums to winter over, they really need to be placed somewhere with excellent drainage. That winter-kills more mums than anything else. Just sog to death.