Sorry about the black flies, Margaret.
In Ontario too, they're much worse than the mosquitoes, but you don't see them in the south where we are.
A friend of mine who fished way up north said they were terrible, but they don't bite through clothing.
Some plants are sometimes sold as "self-cleaning".
Salvaged a lovely mauvey red double flowered rose of sharon from Mrs. L's garden and put it towards the back of our garden.
It was close to the front, previously, and definitely not self-cleaning; thought the dead blossoms detracted from the overall effect of the shrub in flower.
It's now far away enough from the front of the bed that you don't notice the dead blooms and two years after its move it's doing very well.
My most important reason for deadheading is to prevent seeders from reseeding all over the place.
Am assuming that some gardeners, like you, with even shorter growing seasons than us, are now beginning to get very busy with gardening and outside maintenance.
Got to let you get to it.