While this Spirea is well established as a long-term species at the Perth place, the largest patch, in a dry sunny spot, often looks a bit tattered by mid summer. I’ve become convinced that this has more to do with the setting than the species, since plants growing in nearby areas that are seasonally wet, and less likely to get really dry through the summer, remain lush and green until fall.
While I haven’t found these to be fast to spread compared to species like Sumac and Prickly Ash, they do produce offsets and can travel a bit. They are recommended as a hedge species on the Missouri Botanical Garden plant finder (a really excellent website by the way) and I suspect that occasional pruning would encourage a dense, well branched form with plenty of blooms. Their tiny, mid-summer flowers are held in fluffy, cone shaped clusters and are very popular with pollinators of all shapes and sizes. Their seed heads retain the same shape as the blooming clusters and add some texture to the garden well into winter.
I’ve resorted to repeated checking of seed heads to catch them at maturity. They brown before they open but when they are ripe the fine, almost hair-like, seeds will fall out of their rigid little star shaped pods. Once they start to open and you are able to shake some of the seeds free, you can clip the full seed head and bring them indoors for further drying, which will allow more seeds to fall free of the pods.
Without pruning, they grow to around 3’ to 4’ in height and width, making them one of the smaller Ontario native shrub species (except for bog and alvar species, but they don’t always adapt well to garden settings) and one that I think would adapt very well to urban and suburban life. They would also thrive in a mixed meadow setting and would love a spot next to a downspout or in soggy corner of a backyard. I’ve seen them absolutely thriving, and nicely holding their own, alongside Joe-Pye-Weed, Giant Goldenrod and wetland grasses in a very crowded, seasonally flooded area that I drive by regularly on my way too and from the Perth Gardens. I’m pretty sure that White Turtlehead, Blue Vervain, Boneset and Pink Swamp Milkweed would also be very happy in that company.
I’ve mostly noticed these in sunny areas but the internet tells me that they are also happy in partial shade. All-in-all, I think that these are an underappreciated species that deserves to be included in a lot more gardens.