Choosing Perennials

At this time of year, very few of the perennials in my flower beds are still blooming. 

Looking through the mess of leaves, I notice that four different flowers that are blooming...

The white anemones that bloomed in spring are blooming again. They are the only flowers I have that bloom twice.

The tiny red Knautia are barely visible, but they're still there. They have been blooming all summer - though, in recent years, I barely notice them as they were blocked by other leaves and flowers. I'm not sure what to do about that.

The blue geranium that starts blooming in early summer has been blooming all season long.

Fall is the time for Sedum to turn red and bloom. Their flowers remain all winter long, unless they are broken off. I notice some coreopsis flowers near the sedum are still blooming too - though they are on their way out. I enjoy seeing their bright color.

If I were to start a perennial garden over again, I would consider flowers with a longer blooming season. 

But that would probably be quite limiting. Another aspect of  perennial gardening, that impacts things, is the fact that not all flowers adapt to every garden space and soil type. I've planted quite a few flowers that haven't done well and eventually died.

Is it the soil? The pine trees overhead? The sunlight? It's hard to know why some plants do well and others die...