Sounds wonderful! Agapanthus, blue pea vine, columbine, plumbago, iris, corn flower (Centaurea cyanus), spiderwort.

My in-laws did this several years ago. They had a purple leafed plum, lavender, irises (both Siberian and bearded), creeping phlox, and I am sure other plants which I no longer remember. Although I love blues and purples theirs had so many different shades and not much to provide contrast so that it always seemed to me somewhat less effective than it might have been. They have now reached an age that they are having a difficult time keeping up with their gardens, and that bed has been returned to lawn.

My garden is a mix of colors altho I do like blues and purples so have quite a few. Here are the ones I had on my list:

Blue or purple perennial flowers -

Walker's Low catmint, East Friesland perennial sage, Royal Candles Spike Speedwell, Blue Fortune Hyssop, Dwarf Siberian Irises, Bearded Irises, forget-me-nots, Blue (creeping) sedum, Ajuga, Festuca glauca 'Elijah Blue' (a blu-ish grass), lamb's ears, variegated and non-variegated Jacob's Ladder, Columbine, Pasque Flower, Cranesbill, Delphinium (tall & medium), purple loosestrife, Campanula glomerata, monkshood, Mountain Bluet, blue flax, lavender 'Munstead', chives.

I've also in the past grown borage which is an edible annual and the flowers are pretty in a glass of lemonade.

I've put some of my pics of blue and purple flowers in an album.

Here is a link that might be useful: My blue and purple plants

This post was edited by luckygal on Sun, May 12, 13 at 16:55

Thank you to everyone for your suggestions. This is great!! I decided I wanted to do the garden like this last season and am ready to get started again. It has a lot of space that needs to be filled and your suggestions have been great so far! Luckygal, I love your photos! I'm going to have to check into the blue creeping sedum, I've been trying to find a ground cover for some of the areas and I didn't know creeping sedum came in blue.

For contrast, you can put blue next to violet. I love Etoile Violette clematis with blue plumbago.
Blue and violet bearded irises look great blooming together too.

I'm in the process of creating a similar bed, though mine is also supposed to be for the butterflies and hummingbirds and other beneficial pollinators and will contain pinks and whites as well as blues. I have:
Lavender, chives, large and small iris, Jacob's Ladder, Malva, Agastache, Swamp milkweed, New England Asters, coreopsis (pink), columbine, delphinium, larkspur, Wild Blue Lupine (but I don't think they survived last summer), wild petunias, Obedient Plant, snapdragons, several annual and perennial monarda, and I'm starting lots of zinnias and annual asters from seed. I'm trying Torenia and Browallia from seed, also, but I've never grown them before, so we'll see. Good luck. I'll take pictures if the weather ever warms up enough to let things grow and bloom.

Martha

No one has thus far mentioned Stokesia laevis/stoke's aster but it has 2-3 inch fringed lavender-blue flowers & is reliably hardy--at least it has been in my beds for several seasons. In my experience it's virtually maintenance-free and requires little more than decent soil & adequate amounts of sun.

Virginia bluebells/Mertensia virginica are an early-spring, shade-loving ephemeral that provide trumpet-shaped blue color in the garden altho' they disappear completely sometime in late May-early June.

Phlox divaricata âÂÂBlue Moonâ (woodland phlox, wild sweet william) is putting on a show in my part-sun garden at the moment and altho' low-growing, it really pops this time of year.

Platycodon grandiflorus/balloon flower is another reliably hardy, low/no maintenance perennial that's also available in either blue or white-blooming varieties.

Catananche caerulea/Cupid's dart is also hardy in Z6 and blooms in either blue or white altho' it hasn't reliably come back for me.

Perennial flax/Linum perenne lewisii produces tiny but exquisite blue flowers in the early-season garden. It's also native if my research is correct--it was reputedly discovered by & gets its name from the Lewis & Clark expedition.

Lobelia siphilitica/Great blue lobelia is a somewhat tall, late-season bloomer that's popular with bees.

docmom - I saw hummingbirds at my Centaurea - Mountain Bluet this year, if you are looking for another blue :)

Thanks for the suggestion, Ripley.

Garden weed, I have Virginia Bluebells in back, and I wintersowed Great Blue Lobelia this winter and have lots of seedlings. Though, I've heard the lobelia can be quite enthusiastic in its reseeding habits. My bed is right up by the road, so I'm trying to have mostly low-growing plants to allow for visibility for those backing out of driveways. I love your other suggestions, also.

Martha

I am trying out Chinese Houses (purple and white) this year from direct sown seed, as well as Love In A Mist which I believe you can get in blue/purple only. There are some smaller sterile Butterfly Bushes that might work as foundation shrubs as well as the bigger older varieties (depending on if they are invasive where you are or not). Also hydrangea, depending on your soil (if it will stay blue).

docmom/Martha - you'd love the Phlox divaricata 'Blue Moon' I mentioned above. It's low-growing, forms a mound 6-8 inches tall and in my somewhat brief experience is extremely well behaved. I've no complaints about it so far and this is year 3 for me growing it.

My great blue lobelia is planted in a bed that's heavily mulched, with corrugated cardboard under the bark mulch & bordering on a brick walkway so I haven't noticed too much reseeding thus far. Can't say the same for the Adenophora/ladybells on the opposite side of the walkway however. Those appear to be rampant reseeders.

How about pincushion flower (I have Blue Butterfly), vinca is a nice groundcover with blue flowers as is blue star creeper, and how about violets, pansies, violas and johnny jump ups--these all have blooms in the blue/ violet range.

Mine is largely blue, lavender and purple, but I've also mixed in white, yellow, and red, so it isn't quite as monochrome. I've got centaurea montana, baptisia, catmint, iris, sedum Autumn Joy, geranium nimbus & Brookside, brunnera, purple coneflowers, Russian sage, salvia, clematis, agastache, and a few more I am missing at the moment!

eclecticcottage, what is "Chinese Houses"?

Chinese Houses: