Bring on the Blue
Gardeners have a wealth of choices when it comes to blue-flowering plants that add splashes of color to gardens and containers. Whether you live on the coast, have a boggy site, want to create a garden that attracts beneficial pollinators, or just like the color, there's a blue-bloomer that fits your needs and desires.
Options abound for any area, whether you need a salt-tolerant variety, desire one that attracts butterlies, or want vine or bulb.
Blue daze (Evolvulus glomeratus) fills seaside gardens with a constant supply of 1-inch, blue funnel-shaped flowers that bloom for only a day. The perennial's green oval foliage is only 1-inch long and covered in gray fuzz. Considered a small subshrub, mature plants grow into 2- to 3-foot tall and wide mounds, making it suitable as a groundcover, used in containers and hanging baskets, or a border plant. Plants are hardy in USDA zones 8 through 11 and don't require any special care or maintenance as long as they're planted in a sunny site, sandy, well-drained soil and given regular water for best growth and blooming.
Sea lavender (Limonium perezii) tolerates an array of conditions from direct salt-spray to desert heat, making it a hardy and colorful addition in gardens in USDA zones 9 through 11. The herbaceous perennial has a clumping habit, reaching 12- to 18-inches tall and 3-feet wide at maturity. Tall stalks up to 4-feet in height, hold bunches of small blue flowers with white petals and produce a profuse amount of blooms late winter through spring. It grows best in sandy, well-drained soil in sites receiving full-sun and with the only maintenance being to remove spent flower stalks. Sea lavender is suitable used as a flowering border, along paths, and groundcover.
Spiderwort (Tradescantia virginiana) is native to the eastern portions of the U.S., though many cultivars have formed due to crossbreeding. The herbaceous perennial forms large clumps with grasslike foliage that reaches up to 2-feet tall. Blue, three petal flowers form in clumps, with each flower remaining open for only half a day. Blooming begins in springtime and can last throughout the fall though trimming the foliage close to the ground in summer guarantees continued blooms in autumn. Spiderworts prefer constantly moist, fertile soils and tolerate boggy sites, making it a colorful addition to wet gardens situated in partial shade to full-sun. A perennial in USDA zones 5 through 9, it works well used in containers, native gardens, and borders.
Forget-me-not (Myosotis sylvatica) is a suitable addition to rain gardens and wet sites, as the plant grows best with consistent moisture. Small clumps of blue 3/8-inch diameter flowers with five petals and a white or yellow eye appear in springtime and blooming can continue through the summer. Hairy, oblong to straight foliage grows 1- to 3-inches long. The herbaceous perennial has a mounding habit, growing around 6-inches tall and 12-inches wide at maturity and is hardy in USDA zones 3 to 8. Plants work well as a ground cover, in native gardens and the flowers attract butterflies. It grows best in fertile, well-drained soils that retain moisture and in full-sun to partial shade.
Blue spirea (Caryopteris x clandonensis), also called bluebeard, is an herbaceous perennial in USDA zones 4 through 8, but in colder zones 4 and 5, the plant dies to the ground during winter and resprouts in spring. Tiny flowers form in clusters and depending on the cultivar, range in colors of blue, blue-violet, and bluish-purple and bloom in summer throughout the fall. Lancelike foliage is greenish-gray forming on bushes that grow 2- to 3-feet tall and wide at maturity with a rounded habit. The plant is drought-tolerant grown in well-drained soils in full-sun to partial shade. Use blue spirea in borders, as a foundation plant, in mass plantings, or as a specimen.
Catmint (Nepeta x faassenii) cultivars 'Blue Wonder' and 'Dropmore' produce long spikes 12- to 18-inches long covered with tiny blue flowers, which appear in spring through summer. Plants have a loose growth-habit with small green leaves and at maturity grow up to 2-feet tall and wide. This variety of catmint grows as a perennial in USDA zones 4 through 8 though other regions can grow it as a flowering annual. Prune plants down by half after it finishes blooming to maintain a tidy appearance. Once established, the catmint tolerates both hot and dry conditions. For best growth, plant in well-drained soil and water weekly. Its blue flowers brighten borders, work well used in mass planting, mixed gardens, and in containers.
Pincushion flower (Scabiosa columbaria 'Butterfly Blue'), as its name implies, is a wonderful addition to add to butterfly gardens attracting the beneficial pollinators, and the tightly held petals resemble a pincushion. Perennial in USDA zones 3 through 7, the hardy and long-blooming plant produces a mass of bluish-lavender, lacy 2-inch blooms atop 12 to 18-inch plants with grayish-green foliage. For best growth, plant in well-drained, organically rich soil in full to partial shade. During summer, when conditions are hot and dry, add a layer of mulch around the plants to conserve soil moisture and water regularly to keep the area moist but not soggy. Deadheading the spent blooms promotes new and continued blooms. Use pincushion flowers in borders, mixed gardens or inside containers.
Lobelia (Lobelia erinus), also called dwarf lobelia and annual lobelia, has a variety of blue-blooming cultivars with diverse growth habits. Low-growing types average 4- to 6-inches tall and make suitable border plants, whereas, trailing types grow up to 18-inches in length and work well used in containers or as ground covers. Blue tubular flowers bloom in clusters that have two upper lips and three lower ones, are 1/2-inch wide and held on a 2-inch raceme. The long-blooming flowers appear in spring and again in the fall. Toothed green foliage, sometimes with a hint of burgundy and bronze, depending on the cultivar, is straight or ovate and 1/2-inch long. Typically grown as an annual, lobelia is a perennial in USDA zones 10 and 11. In cooler summer climates, plant in full-sun, but where it's hot, plant in partial shade and in well-drained soil kept moist.
Bearded iris (Iris germanica) has various cultivars producing blue flowers including 'Baby Blue Marine', which is classified as an intermediate growing 16- to 27-inches tall, and 'Spinning Wheel', classified as a tall variety growing 28- to 38-inches tall. The plants grow from rhizomes, producing flowers starting in spring through early summer that have three petals on top and three on the bottom. The bottom petals have a fuzzy line running down their center, thus the nickname bearded iris. Shorter types are the first to bloom, with the tallest varieties blooming last. Foliage is green and sword-shaped. For best growth and flowering, plant in fertile, well-drained soil in full to partial sun. If your soil is prone to retaining water, plant the iris in raised beds. To keep the plants blooming, divide clumps every three to four years. Bearded irises are hardy in USDA zones 3 through 10.
Grape hyacinth (Muscari armeniacum) bulbs produce one to three 8-inch flower stalks in spring lined with clusters of blue, urn-shaped flowers that resemble grapes and surrounded by green, 10-inch straplike foliage. Cultivars that also produce blue blooms include 'Blue Spike,' 'Sapphire', and 'Heavenly Blue.' It is hardy in USDA zones 4 through 8 grown in fertile soil that drains well. Water during the growing season of spring to keep the soil evenly moist. Reduce water during the hyacinth's dormancy in summer and as the foliage begins to die in winter. In hot climates, the plant performs best grown in partial shade and in cooler areas, full sun. Divide plants every few years. Use in containers, mass plantings, borders, and mixed bulb gardens for a blast of blue.
Blue skyflower (Thumbergia grandiflora) performs as an evergreen, perennial vine in frost-free areas of USDA zones 10 and 11, and can become invasive. In cooler areas, it grows as an annual. Starting in summer and throughout the fall, clusters of 3-inch, bluish-violet trumpet-shaped flowers with yellow throats appear in clusters, surrounded by 4- to 8-inch, heart-shaped green foliage. Where it is hardy, the vine grows up to 30-feet tall and in areas where it performs as an annual; it reaches a height of 8-feet, with a spread of 3- to 6-feet. For best performance, grow blue skyflower in rich, well-drained soil that receives full-sun to partial shade. The vine makes an attractive addition to containers, fences, trellises, hanging baskets, and grows as a houseplant.
Kentucky wisteria (Wisteria macrostachya) cultivar 'Blue Moon' is a deciduous, perennial vine native to the U.S. and hardy in USDA zones 3 through 9. Fragrant, blue pea-shaped flowers surrounded by green ovate foliage, form clusters on racemes up to 12-inches long and bloom in June and throughout summer. It has a vigorous habit growing up to 25-feet tall and 8-feet wide and requires a sturdy structure due to its weight. For best growth and flowering, plant in a sunny location in fertile, well-drained soil that is slightly acidic and water weekly. The vine doesn't transplant well, so select a permanent site when planting. Use in the landscape on fences, arbors, or pergolas.
Greater periwinkle (Vinca major) is an herbaceous perennial that produces 1.5-inch, blue-violet flowers covering 3-inch, heart-shaped green leaves. Flowering begins in the springtime and continues through fall. Hardy in USDA zones 7 through 9, the plant can have invasive tendencies due to its vigorous growth. Mature plants reach up to 1.5-feet tall and 2-feet wide. For the best performance, plant periwinkles in rich, well-drained soils kept moist. It will tolerate sunny conditions, but will grow best in partially shady to shady sites. Use it in the garden as an erosion-control plant, in containers, hanging baskets or ground cover.
Fairy fanflower (Scaevola aemula) gets its common name from the blue, 1-inch fan-shaped flowers that have five petals only on one side with yellow centers that bloom for months starting in springtime. Toothed, 2-inch foliage forms mounds almost 2-feet tall and 3-feet wide with a sprawling habit making it useful as a ground cover. Fairy fanflower is a hardy and quick-growing evergreen tolerating drought, sandy soil, full-sun, partial shade and salt-spray, making it a colorful addition to coastal gardens. Cooler zones can grow it as an annual, as it tolerates light frost, but it is an herbaceous perennial in USDA zones 9 through 11. Besides working as a ground cover, the plant also grows well in containers, hanging baskets, used in borders and low-water gardens.
Plumbago (Plumbago auriculata) is also called skyflower due to the clusters of 1-inch long, tubular blue flowers that spread into five, 1-inch petals and cover the shrub almost year-round. Thin oblong foliage is greenish-yellow and 2-inches long and forms into a loose mound up to 10-feet wide and tall at maturity. The cultivar 'Royal Cape' produces blooms that are a deep blue. Quick-growing and hardy once established and tolerating drought, plumbago is an evergreen perennial in USDA zones 8 through 11. For the best blooms, grow in a full-sun location in well-drained sandy soil. Due to its fast growth-habit, the plant requires frequent pruning to keep it shaped. In the landscape, use it as a shrub, butterfly gardens, containers or in the garden for a constant mass of color.
Russian sage (Perovskia atriplicifolia) is a perennial, evergreen shrub hardy in USDA zones 3 through 9 and grows up to 5-feet tall and wide at maturity. During late summer, 12-inch long flower spikes fill the shrub with tiny blue flowers. Since Russian sage has a loose upright habit, keep it tidy by pruning down to 1-foot in early springtime. The numerous spikes of blue flowers compliment the 2-inch, greenish-gray and aromatic foliage, making this a colorful summer addition to mixed gardens, large containers, and used for mass color. It is also deer-resistant. It performs best grown in full-sun and well-drained soil amended with organic matter. Once established, the sage is drought-tolerant.
Butterfly bush (Buddleia davidii), also called summer lilac, is a deciduous shrub and as its common name implies, it attracts butterflies and hummingbirds. It is hardy in USDA zones 5 through 9 and in its cooler zones, it reaches a mature height and width of 5-feet before it dies down in winter. However, in its warmer growing range, plants can grow up to 8-feet tall and wide. Starting in the summer and continuing throughout the rest of the year, if pruned after flowering, butterfly bush produces long, 10-inch stems packed with small, fragrant blue flowers. Depending on the cultivar, ovate foliage is serrated and colored deep green, grayish-green, or lighter green and stays on the plant until late winter before dropping. It tolerates a wide range of soil and cultural conditions including drought, heat and humidity, and produces the most abundance of blooms grown in a sunny location, but tolerates partial shade. Use it in wildlife and butterfly gardens, as a specimen, mass plantings, and foundation plant.
Bigleaf hydrangea (Hydrangea macrophylla) is a deciduous shrub that produces blue flowers when grown in soil with a pH of 5.0 to 5.5, as well as having blue-blooming cultivars such as 'Ayesha', 'Nikko Blue', and 'Mariessi Perfecta'. Soils with a higher pH produce pink flowers. Depending on the cultivar, plants produce either snowball-shaped clusters of flowers or clusters with more of a flat-top, with both blooming on last season's growth in summer and surrounded by 4- to 8-inch green foliage. Prune immediately after blooming to shape the rounded shrub so the plant has time to develop new growth for next season's production of flowers. Hardy in USDA zones 6 through 9, the hydrangea grows best in fertile, well-drained soils kept moist and in full-sun to partial shade. Growing up to 3- to 6-feet wide and tall at maturity, the plant is well-suited for containers, indoors, native and mixed gardens for a blast of blue color.
Borage (Borage officinalis) is an annual herb suitable for growing in all USDA zones; however, it can reseed into garden areas. Starting in summer, clumps of bright blue flowers shaped like stars bloom on drooping racemes surrounded by edible grayish-green foliage that is hairy and tastes and smells like cucumber. Plants have a sprawling habit and grow up to 3-feet tall and 1.5-feet wide at maturity, making it a suitable choice used in herb gardens or areas in the landscape where it can spread naturally. A hardy plant, it tolerates an array of well-drained soils, drought and prefers a sunny or partially shady site.
Rosemary (Rosemary officinalis) is an evergreen perennial herb in USDA zones 7 through 10. Clusters of blue two-lipped flowers line the stems and bloom in late winter through spring, and can continue blooming throughout the fall if pruned after flowering. Rosemary's greenish-gray, 1.5-inch needle-like foliage is very aromatic and used for various craft and culinary purposes. Plants have an erect and rounded growth-habit and at maturity can reach 6-feet tall and 4-feet wide. For best growth, plant in a sunny location in well-drained soil that is on the acidic side. It doesn't tolerate soils retaining water or being overwatered and will die -- it likes it dry. Use the herb in container gardens, herb and butterfly gardens, borders, and as a small hedge.
With all the selections of blue flowers suitable for many climates and conditions, gardeners won't be singing the blues because they cannot find a blue-bloomer to grow in their gardens. Including blue flowers in the landscape with other colorful flowers turns a garden into pure eye-candy.