You have to have the right soil PH.
I did once see the most gorgeous vivid blue hydrangeas at someone’s house, once. The woman said it came from her aunt. I dunno what the aunt did to get them to grow that way, but they looked something like this.
Try Salvia guaranitica for a true blue, perennial and a great spreader in Zone 7-10.
Also Veronica ‘Georgia Blue’, a first spring bloomer that is a vivid blue, pretty hardy in most of the US.
Where do you garden, zone wise? That’d help with more recommendations.
The Himalayan blue poppy is my Dream flower for blue. Alas, I am in the South, and have a very green thumb, but Meconopsis won’t grow here.
Malleus, I got to this thread by reading your dayflower question, and have some answers there, but am really pooping out now, as this is my “friday” after my job of talking about plants all week, and it’s spring, so… will answer that thread tomorrow.
Come to think of it, “Roses are red” is also a major exaggeration… lots of them aren’t!
Ah, true. I guess I take it for granted that our soil (mid-Atlantic) produces blue blooms.
Purple is just a reddish kind of blue, isn’t it?
So, yep, not asleep yet, but, so Y’all know, there is an exact guide in the Horticultural industry for flower color; Britain’s Royal Horticultural Society is the standard, with about 900 color variations. I don’t own the guide, as it is absurdly pricey, but, you can pinpoint color accurately by that scale, and it’s used in the trade, with a RHS color designation.
When I was a kid there was a “Blue Garden” in Woods Hole/Falmouth on Cape Cod (Massachusetts). The entire garden was planted in blue flowers and it was absolutely gorgeous. There were certainly variations, but it overall did look blue.
The Cape is famous for the Blue Hydrangeas that only seem to grow blue there. There’s something in the soil, from what I understand, that gives them the bright blue coloring that isn’t found elsewhere. When I was older I wanted to plant them at home, in North Central MA, and was told they wouldn’t grow the same blue color up here. I’ll have to see if I can find the info as it’s been a long time since it was explained to me.
Well, I did find an interesting sitethat explains partially, but still not sure why the Cape is more apt to have them. The salt and humidity from the ocean and the sandy soil must factor in. But this site has some interesting info regarding forcing color changes in hydrangeas.
And I can’t find a reference anywhere so far to the Blue Gardens. We used to go there all the time and I know after the original owners died, their children didn’t want to bother with the upkeep and it was no longer the Blue Garden or open to the public as it had been.
On an episode of Dharma & Greg, Dharma talks about the coveted Duck Award, given to the couple who has sex in the most outrageous public place. When her stuff in-laws end up having sex on the court building steps, she gives them the award.
Mrs. Montgomery: Dharma, this is not a duck. It’s a goose. Why do you call it a duck when it’s a goose.
Dharma: Cause goose doesn’t rhyme.
I have thousands of these dudes growing on the hill and in my yard. Pretty and most decidedly BLUE, not PURPLE. However, I agree that there are more purple flowers than blue.
Depending on the map I’m looking at, I appear to be in either 6 or 7.
Part of that is where you draw the line between blue and purple (or blue and lavender). I have a trademark ‘blue’ that’s rather periwinkle (You can see it if you scroll all the way down here). Depending on what shade I use it’s either more purple or more blue. I’ve had people say that something was purple when it was as blue as I could make it. This was doing graphic design in CMYK. Blue is made with magenta and cyan. Dark blue is always a bit purpley. There’s nothing I can do about it.
Of course, some of those flowers are just plain purple, no quibbling about it.
But then again, lavender’s green.
Commelina erecta, also known as slender dayflower is actually quite a vivid blue. I’ve seen them in person. Blue is also my favorite color. They look more purple in those photos than they do in person. There is little bit of purple in them, but not notable when you see them against their leaves. They are a little bluer even than the main photo shown there, in fact.
That would explain it. I guess that even what we in Britain regard as really hot summers just aren’t hot enough!
How about this one,ceanothus. That one comes form California (and othetr parts of North and South America. They’re in flower over here at the moment and look particularly gorgeous against honey coloured walls. The downside is that they don’t flower for very long.
There’s a couple more common in the UKcornflowers and cranesbill where the petals are blue but with purple veins or sepals.
Dayflowers are one of my favorites, but I can’t quite figure out how to grow them.
Nope. Your “hot” summers are laughably mild to a lot of us. I live in Northern Texas, and we get blazingly hot summers. As in, we have lots of days when the temperature is about 100 F, which is about 38 C. When it’s humid as well as hot, well, sometimes people pass out from heat exhaustion.
On the other hand, we rarely get snow and ice around here. When we do, everyone stops what they’re doing to gawk at the solid state of water that has miraculously appeared. Plus, most of us don’t know how to drive on snow and ice, and our goverments haven’t got the equipment to plow the roads and put sand on them in a timely manner.
If that were true plants would love it. Think about it, being blue would be a warning that you were highly toxic and shouldn’t be eaten! Plants hate being ate with the exception of fruiting bodies and the like.
I’ve heard this version:
Roses are reddish
Violets are bluish
If it wasn’t for Jesus
We’d all be Jewish
Then again the last two lines aren’t exactly accurate either. 
This whole blue flower thing is good to know because I am also a fan of blue and was hoping to plant some plants with blue flowers. I shall be more careful about what I choose now. I like those Salvias.
head explodes