July 4th weekend is here, and what better way to celebrate the ol’ red, white and blue, than by talking about some true blue flowers? Blue is an extremely rare color in the plant kingdom, and finding true blue blossoms is a task to be undertaken with dedication, and the rewards are great. It is important to buy blue flowers in bloom, or if this is not possible to at least have seen a particular variety in color, since many plants sold as “blue” in the horticultural industry are shades of purple or lavender. The true blue connoisseur should never settle for anything less than perfect!

Spring-blooming blue flowers are generally paler shades, to blend and compliment yellow daffodils and other pastel blossoms. Forget-me-nots (Myosotis sylvatica) and Brunnera, Blue Stars (Amsonia), and ‘Blue Bird’ Columbine (Aquilegia) are all early bloomers, sprinkling sky through the garden bed. Forget-me-nots and Columbine both spread quite readily by seed, so a field of springtime blue flowers is a very real gardening possibility. Blue Stars and Brunnera are perfect for sun and shade, respectively, and add their own texture and color, even after the blossoms have faded.

Summertime brings more blue to the garden, starting with the tall, stately spikes of Delphinium, ranging in shades from palest sky blue to deep, saturated indigo. Borage (Borago officinalis) adds blue to the herb and vegetable patch, providing both beauty and a wonderful source of pollen and nectar for the incoming honeybees. False Indigo (Baptisia australis) and Mountain Bluet (Centaurea montana) are deep blue blossoms, tall and bushy for the middle of the perennial border. By early July, those ‘Heavenly Blue’ Morning Glory seeds you planted back at the end of May should be growing up the trellis quite nicely, and display a few trumpet-shaped flowers for those who get up early enough in the morning to see before the sun comes and causes them to close for the afternoon.

There are several varieties of perennial geranium that are beautiful blue; ‘Rozanne’, ‘Johnson’s Blue’, and ‘Jolly Bee’ among them. These bloom tirelessly through the fall once they start, with minimal maintenance required; only a little bit of deadheading and trimming if the plants get spreading too much out of hand. Gentian is a lovely little blue flower as well, suited to rock gardens, or places with well-drained soil rich in humus. Himalayan Blue Poppies (Mecanopsis) are a rare, choice flower, tricky to grow, but so rewarding if they find a place they’re happy in…

Late summer into fall is when the deeper blues come out. Great Blue Lobelia (Lobelia siphilitica) is another tall blossom, suited to sun or part shade, and can grow quite happily in a semi-moist area. The blossom is a true bright blue, with a tiny white eye in the center. Leadwort (Ceratostigma plumbaginoides) is a lovely little groundcover, blossoming from late July through September, and looks just beautiful as an underplanting with Hydrangea. ‘Endless Summer’, ‘Penny Mac’, and ‘Time After Time’ are among several different varieties that will bloom blue when given the proper soil conditions. Acidic soil (which we have, generally, in Maine) turns hydrangea blue, while a more alkaline or sweet soil will cause them to bloom pink. Other fall blooming shrubs with beautiful blue blossoms are the Rose of Sharon ‘Blue Satin’ (Hibiscus), and Blue Mist Spirea (Caryopteris), which must be treated as a tender perennial in this area.

The one flower that has eluded gardeners throughout the ages is the mysterious blue rose. Though now, science has now done what nature could not. Through centuries of careful and selective breeding, a truly blue-colored blossom has never been produced, due to what we now know is the lack of a certain gene that carries delphinidin, the primary pigment that produces blue in flowers. It will never exist in nature, but scientists have produced a genetically altered rosebush that is much more blue than anything previously seen, by inserting DNA from a petunia into the rose. Test batches of these roses are being grown in Japan, so within several years, who knows what we may be seeing!