Blue flowers are scarcer than most other colors. You see a lot of blue flowers advertised in seed and plant catalogs, but nine times out of ten they are really purple. “Johnson’s Blue” geranium? Blue flag iris? Both purple. A blue flowers are coveted, and calling them blue will increase sales. Sometimes photos are tuned up to look bluer. And some people truly cannot see the difference- I’ve stood before plants that obviously looked purple to me, and had the owner proudly say “Blue!” So, which plants can really claim to be blue?
First, despite all the names, there are NO blue roses. All the older roses called ‘blue’, like ‘Blue Moon’ and ‘Blue Girl’, are really lavender (likewise with ‘silver’ roses- they’re either white or lavender, too). The newer crop of ‘blue’ roses, like ‘Outta the Blue’ and ‘Midnight Blue’ are all darker purples. Beautiful, but not blue. There are not blue petunias, either, despite every strain of petunias having a ‘blue’ in its line up- ‘Blue Daddy’ is lavender while most, like ‘Supercascade Blue’ are deep, velvety midnight purple.
One of the best sources of blue in the garden is the delphinium family. From the palest ice blue ‘Magic Fountains Sky Blue’ to the medium blue ‘Pacific Giants Blue Bird’ to the brilliant deep blue of ‘Blue Jay’, delphiniums provide a total range of true blue. Blooming in mid-summer, they will repeat the show again in late summer if you cut them back right after blooming. Place these tall beauties against a wall or fence, in the back of the border, where they can hold court over shorter plants. Tie or stake well, and feed heavily.
Some of the veronicas are true blue, also, although many are purple. ‘Royal Blue’ is true blue, and reblooms. It’s a rather floppy plant that never stands upright, which makes it perfect for a design trick I like- blue flowers as a stand in for water. I was putting plants along a dry stream bed that butted up against a block wall. Needing something to conceal this abrupt emergence, I put in a couple of these ‘Royal Blue’ veronicas. The blue flowers, spilling over and out of some of the rocks, gave the idea that perhaps this stream had an artesian source at the wall, which I then softened with some taller plants. Veronica peduncularis ‘Georgia Blue’ is a shorter, smaller plant that is also true blue and has the same sprawling habit. Annual lobelia is a good plant to use in the water
Annual lobelia is another good plant for this watery look if the area is shady. 'Crystal Palace' is variable, with some seed lots being true deep blue and some with a touch of purple, but it's worth it to find a reliable supplier. 'Cambridge Blue' is a true sky blue.
A lesser known perennial, Anchusa azurea (Bugloss) has a Latin name that tells the truth- it is indeed azure. While the leaves are painfully hairy -not a cuddly plant- and course looking, the flowers are lovely intense blue stars. Listed as an early spring bloomer, I've known it to bloom for two full months and then repeat again in fall. This plant must have excellent drainage or the hairy rosettes will rot in winter. Don't expect blooms the first year and in fall cut back and clean up the leaves before they turn brown. They are much pricklier when dried up and brown! While not a problem in the inland northwest, this plant has become invasive in some other areas, so keep an eye on it if it tries to spread.
Anagallis monellii is should be perennial in most of Spokane but isn’t in my zone 4 garden, but it grows so fast from seed that it makes a good annual. It's a crawler with dark lapis flowers that open and close according to the weather, which gave it the common name of 'Weatherglass'. As a ground hugger, it works well in a container or at the feet of an upright plant.
There are a few true blue perennials that I'd love to have, but don't have the climate for. Meconopsis, the Himalayan Blue Poppy, is supposed to be a stunner, but is very finicky about its soil, heat and cold. The blue corydalis, like 'Blue Panda', are much easier but aren't cold hardy enough for where I am- although they are in most of the inland northwest. They are lacy little plants that look wonderful in a woodland or shady setting. And commelina, a cousin of tradescantia, has very intense cobalt flowers. It's shorter than tradescantia, topping out at 6-12". I tried lifting the tuberous roots and treating them like dahlias, but they would have none of it and died before winter was half over.
For a cheap- and ineradicable- carpet of pale blue, sow some forget-me-nots. Myosotis will not usually bloom in its first year but after that, you will have it forever. Blooming early and for a long period, it can provide a solid ground cover. When the bloom becomes sparse, cut it back or pull it out before it can develop mildew. By this time it will have dropped enough seed to sprout plants for next years bloom- actually, they drop enough seed to cover the entire world if not kept in check. Another super easy blue annual is annual Bachelor's Buttons. Available in dark, medium or light blue, they will also perpetuate themselves given half a chance, but not to the extent of being a problem. I've seen them growing on the edges of hayfields, surviving but not taking over. No matter which shade of blue you start with, the dark ones will eventually prevail. Nigella - not the TV chef- comes in blue, 'Miss Jekyll' being the most available one. Be ready to thin them, because they are variable and some will have some purple to them. Keep those from setting seed, allow the true blues to do so, and you should have them forever. They are wonderful plants with an odd, almost skeletal appearance, starry flowers, and weird, bulbous seed pods. Most blue pansies have a purple cast to them, but ‘Morpho’ is a blend of pure mid-blue and yellow; ‘Lake of Thun’ is a clear, dark blue.
A couple of other plants are self seeding without being pesky: borage, a cucumber flavored herb, is related to anchusa and has the same star shaped flowers but in a lighter hue. Occasionally the flowers are pink or even half pink/half blue, all on the same plant. Its hairy leaves flop about in an appealing way. Chicory, known as a coffee substitute in New Orleans, has medium blue flowers that open in the morning and close when the sun gets bright. The leaves look like dandelions, and it runs the risk of being weeded out unless it's in bloom. And, of course, Heavenly Blue morning glories, those brilliant trumpets. Plant them on the east side of the house, and they'll stay open longer than on the south side.