I've seen spirea in the northern wilds, but I always assumed it was a native one...maybe not?

Spiraea japonica is considered invasive across much of the midAtlantic area (and moving north) and portions of the southeast.

I haven't planted japonica since I was a teenager..so no danger here :0 Plus I don't see it in my area, I'd recognize a spirea (even if not the species maybe).

But it goes with my theory that all things japonica or chinensis have potential for being invasive here (so like it's native climate).

Dbarron there is plenty of Spirea tomentosa in wet areas of the northern wilds.

Now that I've looked up pictures of Spirea japonica, I recognize it from a lot of commercial properties and new housing developments around here.

There are several varieties that are supposed to be sterile (or nearly so):

Crispa, Dart's Red, Double Play Doozie, Neon Flash, Pink-a-licious

Has anyone attempted to get rid of the ones at Gunpowder Falls?

Of those listed above, only the Double Play series and Neon Flash are species of S. japonica. There are many other species and named cultivars of spiraea that are not freely seeding or invasive.

I'm certainly not the expert in spirea taxonomy, but I believe the above varieties (except Pink-a-licious ) are often listed as S japonica, and Pink-a-licious may actually be a hybrid with japonica per this webpage. See also this abstract regarding sterile varieties of S japonica.

There were a few goldflame sprieas growing here, for a few decades, and there were never seedlings or massive spreading at all. Probably too cold and dry here, or maybe too hot? Too short a growing season? Location?

The first two are both cultivars of x bumalda, not japonica (despite what some catalogs or nursery sites may list). And Pink-a-licious is a cultivar of S. fritschiana.

As with any plant invasive tendencies will depend heavily on location.

gardengal - point taken, but it seems the x bumalda varieties are often listed as japonica (I assume because as hybrids they are difficult to distinguish from japonica?). The article regarding Pink-a-licious says "the likely pollen parent is Norman Spirea".

Agree with Jay that the non-sterile varieties don't seem to be much of an invasive threat here.

Spiraea taxonomy is muddled at best :-) And it doesn't help that European conventions seem to be different from that here in this country. Even the abstract you quote has cultivar listed that are not considered to be japonica here in the US but rather the hybrid x bumalda. Only a DNA analysis could confirm for sure :-)

Same with Pink-a-licious. A suspected pollen parent is not the same as a confirmed pollen parent. It might just be the result of a random seedling of fritschiana, under which species it is consistently listed.

Spiraea x bumalda is an incorrect name for Spiraea japonica. I am certain that Spiraea 'Crispa' and Double Play Doozie® are sterile. But I do not believe that Neon Flash or Dart's Red are sterile. I have never seen Spiraea japonica growing or seeding into the wild here in Michigan. But if it is a problem in your area, I would suggest you use these sterile varieties. 'Crispa' is a very dwarf variety with crinkly, dark green leaves. It is a bit of a collectors plant and hard to find. Double Play Doozie® is new variety from NCSU. As a sterile triploid (3x), it is seedless and puts its energy into making new flowers all summer long.

" Spiraea x bumalda is an incorrect name for Spiraea japonica. "

Sorry but that is incorrect. Spiraea x bumalda is a legitimate hybrid between S. japonica and S. albiflora, which is now recognized as a distinct species rather than a subspecies of japonica. It is taxonomic confusions such as this that result in mislabeling. But because both japonica and albiflora are commonly called Japanese spiraea, it is easy to see how the confusion arises.

I stand corrected. At the time I came to this conclusion albaflora was listed as a subspecies of japonica and thus x bumalda would have been a hybrid within one species. I see now that recent sequencing data has show them to be two distinct species.

Gardengal, how do they decide to recognize it as it's own species, if they already know it's a hybrid. Botany professors decided this?

Jay, I think you misunderstood my comment. Spiraea albiflora has been determined to be a separate species, whereas formerly it was considered a subspecies of S. japonica. If it had not been spun off on its own, that would make Tom's comments valid.......you can't have a true hybrid within a single species. And that no doubt accounts for a lot of the confusion with these plants.

Any decision to separate or divide a species is based on enough evidence to support a definitive distinction between the two. And that is usually determined by botanists, in this day and age often as the result of DNA analysis.

Tim - have you observed Neon Flash and Dart's Red producing stray seedlings (here in MI or in other areas)? Any observations regarding Superstar (= 'Denistar')? Superstar's patent says "no seed development observed".

I do think more data is needed on which varieties/cultivars of both japonica and x bumalda have significant invasive potential, and those varieties should be avoided in regions of the country where the species has already been shown to be problematic.

Arbordave I’ve not seen escaped spirea anywhere.