I am wondering if taking up space in my garden is worth it for the time they bloom? Are there plants w similar blooms/colors that bloom longer and still return every year? I like mums, but I kinda feel the same way about them, they get large and bloom for 2 mins.

What about echinacea?

I do have some coneflowers, but have not found any that are blue colored. Are there any blue ones?

Oh, oops. Didn't notice you were asking about blue flowers. Heh, all my asters have been pink.

I get a good bit of color from asters (pinks and purples), although the knees are always a bit bedraggled looking so I'm trying to figure out what to plant in front of them to hide the uglies.

Have you looked at Scabiosa? There are annual and perennial varieties.
(Heh, looks like they changed the name on me...again!)
Pincushion Flower (Lomelosia caucasica)
There's also a very pretty looking blue one:

For some flower-colour in fall, we've depended on perennial asters for years, especially New England asters (notably 'Alma Pötschke' (magenta) and short 'Purple Dome') and a smooth asters, 'Bluebird' (powdery blue) (see the three in picture below: October 6, 2016). We've used several hardy perennial mums (bloom a bit earlier) but, overall, the asters are more showy.

New England asters are prominent among the fall-blooming wild flowers here, though we've used garden seleections which are likely much better behaved in a garden than the seeding and running wild types.

Here, our fall asters are good for a month or more of colour (most of September into October). Several need staking and drought will reduce the bloom time. Have used some really nice perennial aster fillers too, notably calico aster and white wood aster. Re formal names: none of our asters mentioned are still formally included in the Genus Aster but have been reclassified.



A taller New England aster along with variegated-leaf phlox 'Nora Leigh' (latter, unlike any other tall phlox we've had, is an exceptional fall perennial, at least here). Picture September 16, 2017.

thank you, that was helpful to know! Also did not realize the phlox would bloom in the fall like that. I may have to try some phlox sometime!

Don't want to mislead anyone, Deb.

I'm a big phlox (Phlox paniculata) person. We currently have about 30 named phlox cultivars in our garden and so have some experience with them. 'Nora Leigh' seems to be more or less unique among all our phlox cultivars for looking so nice in September and on into October. All of the others have already bloomed and rebloomed (with deadheading) by mid-September, most well before then.

'Nora Leigh' is a later flowerer, but we have so much of it for its foliage. I'm quick to cut back our phlox at the early sign of powdery mildew, but don't remember having seen powdery mildew on 'Nora Leigh'. It seems so odd that a variegated-leaf phlox is so mildew-resistant, when you tend to think of variegated perennials as weaker (viz. better behaved) than the non-variegated forms. Perhaps the fact that it's a late flowerer is a factor and perhaps my focus on continually cutting back summer and early fall bloomers (to expose the lower spring bloomers to light and water) also helps the plant to fend off the mildew.