This is from Bachman's in the Twin Cities:

"Pruning spirea is easy if you think about when the specific variety blooms. Those that bloom early in the spring such as Bridalwreath and Snowmound should be pruned right after they flower because they bloom on old wood. Spring bloomers are usually trimmed for shape and to contain the size. Like lilacs, they can become woody and unproductive as they age. In that case, the oldest stems can be cut out at the base of the plant to encourage new growth. Summer-blooming varieties such as all of the Spirea japonica and S. bumalda should be pruned in early spring. They bloom on new growth. To keep them full, summer-blooming varieties are often pruned back hard, removing 1/2 or more of their growth. The fading flowers of summer-blooming varieties can also be pruned off if you find them unsightly."

I have both Bridal Wreath with white flowers and Anthony Waterer with pink. The rabbits chewed my Anthonys down to the ground under the snow cover this last winter - they rebounded beautifully in a very short time; really lush. I've deliberately taken Bridal Wreath down almost to the ground after it blooms. That comes back, too. I think Spirea might be one of those plants that you just can't kill no matter what you do to it.

I'd be bold with it - can't be any worse cut way back than it is as something scraggly. Next spring's regrowth might surprise you.

Over in the New to Gardening thread I asked for some clarification for pruning instructions about my Spirea. You may find the response I got there helpful.

I actually have two. I think the smaller one in the back was an offshoot. I have it cut down to the ground 'to get rid of it' in the past and it has always bounced back. (Thank goodness).

Spirea is a lovely, winsome, deceptively strong thing.

Here is a link that might be useful: spirea pruning instructions

shrubs... which spirea are ... NEVER need fertilizer .... which is probably indicated by the fact that it has been there for decades...

good luck

ken

In my - admittedly little, which is the point, you can cut them hard and they'll look much better (it may take a couple years, or it might have for me because I was timid). I had 8 spirea in front of my house, also of indeterminate age. They'd died out underneath and though they still flowered, were definitely scraggly. With no knowledge and just some shears, I started deadheading at first, then got bolder and started cutting them back harder. Because mine were still foliated and blooming on top but sticks underneath, I cut back the tops harder to get light to the underneath, as well as removed tons that were just rigid and clearly never going to bloom again. Like I said, after a couple seasons of this, they are lush and supporting a million bees with their flowers. You'd probably have better results doing it the right way and more systematically, but even just chopping them back as I did resulted in pretty happy shrubs.

I've never had any problem with cutting them back, in fact some have looked better. Some overgrown ones once caused me to fall down the steps and they got mercilessly wacked. They came back full and strong - and improved.

This post is old but still very relevant to me. I'm glad I found it. I have 12 yr old spirea in the front (west facing) of my home that are mostly sticks now underneath and look terrible. I have always trimmed them a little, but never hard pruned them back to only 8 inches off the ground. I may well do it this year because they look so sad. They are green and flower two different colors on the same bush (pink and purple).

hey marie

check out the link ..

ken

ps: two colors.. are you sure it not potentilla??? regardless.. it doesnt matter ... cut them almost to the ground after flowering [unless you dont mind giving up next years show] ... and they will be back to half the size by summer end ... i trimmed my 4 foot spirea to 3 inches.. and within 2 months.. it was back to 3 feet ... but a much more tamed size [its no longer 8 feet wide] ... if that makes sense ... the other one better be ready after flowering next spring.. lol ... because i will be revving the truck .... BTW.... i also dug up 9 rooted branches.. too bad i didnt have a use for more ...

Here is a link that might be useful: link

go ahead & cut them back & as long as you don't harm the roots, they will be fine. it's kind of like the plants are thinking "look at me, don't I look pretty" but, when you cut them back, "oh, I guess I'm not so pretty, I need to do something about that". so, they start over & look better the next time. I know I'm kinda wierd thinking that, but, that's what I'm thinking every time I cut back a plant. it usually works for me. it takes time for them to bounce back, but they will. good luck.

I must be lazy but when mine get too scruffy looking I just run the mower over them and by next year I have a great new plant.I would rather have no plant then a scruffy mess. They grow back real quick.

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

YES! This is exactly what I have. As we're still in the cold throes of Spring in the midwest they are only starting to even leaf right now. I will chop them down in the summer after they flower and cross my fingers for next year. They look terrible right now.

I have whacked my 'Magic Carpet' spireas almost to the ground before and they bounced right back. I did it because they were much bigger than they were supposed to be.

An old post, but a note to say it is Fall here now inzone 5 and I had the landscapers cut back all 5 of my Spirea Japonica practicalyl to the ground. I am hopeful this will rejunvenate them for next year.

Thanks for the advice all

dgmarie -

For your future reference, I often prune mine to the ground in early spring, just as they are starting to leaf out. Mine are under where the snow lands if we get so much snow that I have to rake the roof, and needless to say, the plants get totally squashed. When that happens I wait for the snow to melt and then whack them back. They rebound without problems and bloom as well as ever.

I cut to the ground a few overgrown spiraea in my parents' yard last spring,I didn't intend on it. I guess the OCD got the best of me and I just kept cutting. Regardless, they look better than ever. Much more lush, smaller in form but much more full looking, if that makes sense. Go for it--you won't regret it.