Most blue flowers are blushed with purple to some degree. Except for lily of the Nile, true blue flowers are quite uncommon. Even with their yellow centers, the tiny daisy flowers of blue marguerite, Felicia amelloides, seem to be too blue to be real. They are almost expected to fade to lavender. Bloom may not be as full as it was a month ago, but continues as long as the weather is warm.
Mature plants are usually less than a foot and a half tall, and not much wider, with a symmetrically rounded form. The branches are rather fragile, and can be broken by something as trivial as a clumsy cat. They really are not strong enough for bouncy dogs or children. Yet, their tiny oval leaves are just raspy enough to deter deer. Unfortunately, blue marguerite plants live only a few years.
When first created by Chrysler, the Imperial was considered to be so close to perfection that fancy colors were unnecessary. It was originally only available in black or white, and later red, like the Chrysler Imperial rose that was named for it. It took a while for other colors to become available. Perhaps perfection is the same reason why nierembergia is only blue or white, or maybe purple.
Nierembergia is most popularly grown as a warm season annual for color from the middle of summer to autumn. It can get half a foot high and a foot wide. As a perennial, it has the potential to get twice as high and wide after its first year, but it lasts only a few years, and looks rather shabby through cool winter weather. The small flowers are evenly dispersed over the finely textured foliage, lacking only on the shaded sides of the densely rounded plants.
Because it gets a bit deeper than most other annuals, nierembergia is a nice transitional plant between lower annuals that might cascade over the edge of a planter in front, and higher or more upright perennials or shrubbery that might obscure a foundation behind. It can work alone too, but does not cascade from planters, big pots or hanging baskets.
This one is no fun to handle. It is just as prickly as it looks. Yet, it is the spiny foliage and blooms that make ‘Big Blue’ sea holly, Eryngium X zabelii ‘Big Blue’, so appealing. The knobby blue thistle flowers are centered on prominently flaring grayish blue bracts that look like metallic snowflakes. The intricately lobed grayish foliage contrasts splendidly with just about any darker green foliage.
Bloom begins with summer and continues almost to autumn. The first flowers are solitary on strong stems. As they fade, sideshoots from these original stems continue to bloom with smaller but more abundant flowers. They are excellent cut flowers, fresh or dried. However, cutting the first solitary flowers with long stems removes some of the sideshoots that would otherwise bloom later.
Mature plants can get three feet tall and half as wide. Shade, even part shade, causes irregular growth that can be quite weedy. Although perennial, ‘Big Blue’ sea holly might live only a few years.
Contrary to the appearance of the bristly thistle like foliage and flowers, sea holly is in the Umbelliferae family, which means that it is more closely related to celery and carrot than it is to artichoke!
The delightfully clear sky blue flowers of blue plumbago, Plumbago auriculata, seem like they belong with colorful annuals or in a tailored border of colorfully blooming perennials. However, the rampant canes of mature plants are really best in the background where they have room to grow wild. The canes do not climb like vines, but can flop over other shrubbery as high as fifteen feet.
Rounded trusses of small blue flowers begin to bloom sporadically by the end of spring, and continue to bloom in phases until late summer. Supposedly, each subsequent phase should be a bit more profuse than the previous; but not all plants are aware of this. They might bloom best in mid summer, and less profusely later. ‘Alba’ blooms white. Pale foliage indicates a need for fertilizer.
Blue plumbago is not as easy to work with as it seems to be. Once established, it can grow like a weed, and really seems to take care of itself, and it is probably better to allow it to do so. It does not like to be shorn into hedges or geometric shapes as it so often is. Shearing ruins the natural form, eliminates most of the outer canes that provide bloom, and exposes sparse interior growth.
Most of the brachyscome found in nurseries nowadays are the annual Brachyscome iberidifolia. Perennial species are rare. The name is still often spelled as ‘brachycome’, without the ‘s’, as it had been spelled for decades. Although it is a warm season annual, brachyscome is also popular now because it can bloom better through the locally mild winters than the warmth of mid summer.
The blue, lavender, pink, yellow or pale white flowers are like tiny aster flowers. The finely textured foliage forms soft mounds about a foot deep, or mixes nicely with sturdier plants. Brachyscome might work better as a component to urns of mixed annuals rather than as a uniform bedding plant. It likes full sun exposure, but tolerates a bit of shade. Deadheading promotes continued bloom.
Like euryops daisy, sweet pea shrub and New Zealand tea tree, the blue hibiscus, Alyogyne huegelii, blooms whenever it wants to, even if it wants to bloom sporadically through winter. It should bloom more abundantly in phases though spring and summer, but even that is difficult to predict. The three inch wide flowers are lavender blue, but can be rich purple or white. Pink is very rare.
Young plants can grow quickly but sparsely. Lanky stems can be tip pruned after a spring bloom phase to promote branching and improve density. Growth slows with maturity. Plants can get five feet high and wide in their second year, but might never reach the eaves. They like full sun and shelter from wind, but should not mind a bit of shade. Established plants do not need much water.