The spirea blooms in the spring. There are quite a few kinds, but the one I have puts forth massive cascades of white florets. Each floret is composed of a few little flowers. The florets are rounded in shape and cover the entire spirea bush at the height of blooming time in May.
The spirea bush could well be a "poster child" of Marilynn's Master Gardening because it requires NOTHING but decent sun to grow well (assuming rainfall meets what is normal or even a bit dry for Michigan--it is not a desert plant and it most likely wouldn't want a marsh either!)
No fertilization is required--and that's with POOR SAND for soil. If you don't prune it, its long cascading branches will eventually hit the ground, and can start new plants.
If you DO prune it, you can get more flowers out of it for a spectacular display, but if you ignore it, it won't get ugly on you, either. In fact, ignoring it is an easy way to get more bushes. Once the branches which brush the ground take root, just replant the new ones elsewhere.
Basic pruning techniques are to get rid of dead wood, and to make the cuts right after a leaf node (so there aren't any sticks sticking beyond the leaves at the end of the branch...). But spirea have so many branches that it would be a major pain to get too fussy about the exact technique! Fortunately, you can just chop these back butcher-style and they'll be beautiful again in about 2 weeks ;-) ! Just don't take too much off--have some leaves left when you're done. I've successfully cut about 1/2 off of mine with no long-term ugliness.
WHEN TO PRUNE a spirea bush? Right after it's done blooming is the best time. That's late spring-early summer.
Here's a picture of my spirea from a greater distance. It was last pruned about 1 1/2 years ago. (It only gets pruned when it grows so much that it starts blocking the footpath...about every 2 years, more often if there's a lot of rain.)
About the only thing that ever bothers these is aphids. Aphids like to congregate on spirea bushes in early spring by the thousands!!! There's a variety of ways to handle this occurance. I have tried all of these methods:
You can ignore it but after a few seasons there will be so many that they'll have to be dealt with (or they will harm the appearance of the plant) unless there is something to balance their population (like predatory insects or weather that they don't like). If there's only a few, you can safely ignore them because in the summer the spirea gets woody and unappetizing to the aphids.
You can use organic controls like horicultural oil or ladybugs. Horticultural oil is frankly a big pain because you have to get out there every couple of days (or daily) and respray it (it has no residual effect), and any aphid that doesn't get wet down with it will live.
Spraying them off with water is a joke with a serious infestation of aphids on this plant. They just crawl back up...
Ladybugs (a.k.a. ladybeetles or lady beetles) are my preferred method of dealing with the aphids. They don't work as fast as spraying, but their larvae go on a seek-and-destroy mission against aphids (the larvae eat aphids) and with a decent amount of ladybug larvae, there will not be one aphid left after a couple of weeks! Plus, once you have enough ladybugs in the area, you can use the ignore it method and the aphids will never get out of hand again!!! Don't be fooled by what appears to be a slow eating process if you happen to see a ladybug larvae (also known as an aphid lion) at work. Those aphids will ALL be eaten!
One thing to note is that aphid lions (ladybug larvae) are UGLY--don't kill them off by mistake. Plus, when they are mature, they will turn into pretty ladybugs!
If waiting two weeks for the solution to work isn't for you, and the idea of going out daily with horticultural oil isn't appealing, you can blast them with Diazinon spray. Diazinon is a Chemical method of control. Unfortunately, it's not all that long-lasting. You can expect to diminish the problem for about two weeks with a spraying of diazinon, but it will not eliminate all the aphids (unless you have perfect skill at hitting every plant surface). And they seem to reproduce fast enough to be back in full force as soon as the Diazinon wears off. And it wears off fast enough to allow plenty of aphids back in just a couple of weeks.
Malathion is junk. It doesn't work worth beans and that's that--every bug in my area that I've sprayed that on has reacted as if I used plain water!
The leaves on a spirea are a bit too thickly spaced for chemicals to have a good effect since it's so hard to hit all the surfaces. For a chemical solution to work in this situation, it would have to be a systemic (goes through the plant's system) variety so if you miss a few leaves/branches it wouldn't matter.
I prefer the ladybugs (lady beetles). The adults are pretty and the larvae kill the aphids automatically!
Other than the aphids, there are no problems
whatsoever with spirea in the area covered by this site (Michigan--Midwestern
United States/South-Central Canada) and the plants bloom beautifully. Even the
aphids go away one way or another, once the new stems become woody. Spirea is
a perfect plant for those who want the beauty without the work!