I hate my snowmound spirea not only for the reasons you mentioned but because they have so much dieback.

To answer your question...I dug up two and they sat in a hot garage....it took 3 weeks for them to die.

The few I have left I cut the heck out of them after they flower which will be in about 1 week.

Ken, it's been my experience with just about any spiraea that it can be cut back at any time during either the dormant OR growing season without any ill effects :-) Like potentilla (which I detest), these are about impossible to kill. I routinely cut back my 'Magic Carpet' several times during the growing season to remove the ugly pink flower buds and encourage new foliar growth. And I had an old bridalwreath spiraea that grew too large too fast and I'd often take that one down back to ground level. It would respond by coming back stronger than ever and bloom reliably the next season. I finally pulled it out altogether as it was always visited by huge colonies of aphids. And no manner of pruning seemd to slow it down.

Marie's plant might be Spiraea japonica 'Shirobana' which has flowers of white, pink and red.

If it is a Potentilla, as Ken suggests, don't cut it back to the ground. That will weaken it badly and possibly kill it. Potentilla fruticosa needs a light shearing over after flowering, not a hard cut back into old wood.

Here is a link that might be useful: Spiraea japonica 'Shirobana'

Cut the whole thing down low for a renovation pruning.

That is truly bizarre - I am certan I posted my comment to the thread about a middle aged spiraea. The one where Ken wondered if it was apotentilla. How has it appeared here?

Flora, Ken had a link in that new thread to this old thread. Perhaps when you posted you were still on this thread.

tj

bump

Yes Ken you can!

I have two fairly large ones that flank the front porch steps. Not the best decision for this location but I had just purchased home with No landscaping at all and I had limited money left.

I don't seem to have an issue with branches rooting, probably because mine never touch the ground ;) It does get very thick and crowd the steps and adjacent hosta. I just grab the loppers or pruners and have at it. Never skips a beat.

I'm not big on the 1/3 cut method. Partly because I'm lazy but mostly because I grow plants for my enjoyment not theirs. The most thought I will give to a major pruning is for shape. With my snowmound sometimes that might be an 1/3 but sometimes its over 1/2.

Carp! On my way out the door to my daughters and didn't pay any attention to the date of Ken's OP. Just ignore my post. :)

If Ken is a procastinator...

Carp? Now that's funnnnnnny. Yelling fish when upset!

the problem with the 3 year rule for me..

is that i delay.. and am usually 5 years to late... and by then.. its pissin me off so bad.. i am not going to look at it for 3 MORE YEARS ... lol

ken

I have a hedge of them. I've cut it to almost to the ground twice and it keeps coming back for more. I bet if every 2-3 years you took it to the ground it would live just fine, plus look great.

I would do it to mine more but I get so many ladybugs living on it I would hate to take away their home. I pick them out and set them on other plants to keep them aphid free.