Blue Hydrangea

A big, blue hydrangea is absolutely breathtaking. You can get your bigleaf hydrangeas to turn sky blue by increasing soil acidity. Adding soil sulfur is one way to do this. Bigleaf hydrangeas typically flower on last year’s growth, so if you need to prune them, do so right after they finish flowering. And look for newer varieties bred under the name Endless Summer, which produce flowers on both new and old growth.

Name: Hydrangea macrophylla selections

Growing Conditions: Morning sun and afternoon shade in moist, well-drained soil that’s rich in organic matter. Don’t let bigleaf hydrangeas get too dry.

Size: To 7 feet tall and wide, depending on variety

Zones: 4–9, depending on the variety

Plant it with: Blue bigleaf hydrangeas look stunning when paired with white-flowering varieties such as ‘Annabelle’ or oakleaf.

Buy It: Let’s Dance Rhythmic Blue Hydrangea ($36, The Home Depot)

Perennial Geranium

Plenty of plants offer purple flowers that lean toward blue, but ‘Rozanne’ perennial geranium is one of the best. This long-blooming geranium flowers from June until frost, producing a nearly endless supply of violet-blue flowers.

Plant Name: Geranium ‘Rozanne’

Growing Conditions: Full sun to part shade in moist, well-drained soil

Size: To 2 feet tall and 3 feet wide

Zones: 4–8

Plant it with: Because geranium plants start flowering in early summer, pair it with spring-blooming bulbs such as grape hyacinth, crocus, and white daffodils to add color before this perennial gets going.

Buy It: Rozanne Everblooming Geranium ($28, Breck’s)

Delphinium

Delphiniums offer some of the truest blue-color blooms available. Though perennial, these plants are short-lived and don’t do well in heat and humidity, so sometimes they’re treated like annuals. Stake taller delphinium varieties to keep their flower spikes from toppling over in the wind. Grow them in soil rich in organic matter and provide a balanced fertilizer to encourage the best blue flowers.

Plant Name: Delphinium selections

Growing Conditions: Full sun to part shade and moist, well-drained soil

Size: To 6 feet tall and 1 foot wide, depending on type

Zones: 3–7, depending on type

Plant it with: Blue-flowering dwarf delphiniums such as ‘Butterfly Blue’ or ‘Summer Nights’ look fantastic with the yellow blooms of Coreopsis ‘Moonbeam’ or ‘Fanfare’ blanket flower.

Heart-leaf Brunnera

A gorgeous, but underused, shade plant, brunnera (which also goes by the common name Siberian bugloss) produces sprays of tiny, pale-blue, spring flowers that resemble forget-me-nots. Add to the color show by choosing a variegated selection, such as ‘Jack Frost’, ‘Silver Heart’, or ‘King’s Ransom’ (shown here), which have silver-splashed leaves.

Plant Name: Brunnera macrophylla

Growing Conditions: Shade and moist, well-drained soil

Size: To 2 feet tall and wide

Zones: 3–7

Plant it with: The springtime flowers look fantastic paired with white or yellow daffodils or with silvery Japanese painted fern.

Buy It: Silver Heart Siberian Bugloss ($23, Breck’s)

Grape Hyacinth

A small but beautiful spring-flowering bulb, grape hyacinth produces clusters of blue flowers in midspring. You can also find varieties that bear purple, white, or yellow flowers.

Plant Name: Muscari

Growing Conditions: Sun or shade in well-drained soil

Size: Up to 8 inches tall and 3 inches wide

Zones: 4–8

Plant it with: Yellow daffodils are a classic choice, but you can extend the season by planting with late-spring-blooming perennials, such as columbine, that keep the color show going after grape hyacinth has faded.

Buy It: Blue Grape Hyacinth ($9, Breck’s)

Clematis

Blooming in a range of colors, clematis is a beautiful vine to add to your garden. The true blue-flowering varieties include ‘Crystal Fountain,’ ‘Ice Blue,’ or ‘Arabella.’ Give these vines a trellis or another support to climb.

Plant Name: Clematis selections

Growing Conditions: Full sun and moist, well-drained soil

Size: Most clematis climb to about 12 feet, but some can reach more than 25 feet.

Zones: 3–9, depending on type

Plant it with: A classic way to grow clematis is to combine it with climbing roses. Create contrast by planting a blue-flowering clematis with a yellow rose, such as ‘Graham Thomas Climbing’, or a white type like ‘Climbing Iceberg’.

Bluestar

As you might guess, bluestar features starry blue flowers that appear in late spring. This native plant is also heat, drought, deer, and rabbit resistant. The foliage turns a beautiful shade of yellow at the end of the season.

Plant Name: Amsonia tabernaemontana

Growing Conditions: Full sun or part shade and well-drained soil

Size: To 2 feet tall and wide

Zones: 3–9

Plant it with: Columbines are perfect companions for bluestar. Create a harmonious color scheme by planting blue- or white-flowering columbines; create contrast with yellow varieties.

Buy It: Blue Ice Amsonia ($50, Nature Hills)

Leadwort

Also called hardy plumbago, leadwort is a vigorous perennial groundcover. It puts on a show at the end of the season with its sky-blue flowers and rich red fall foliage. This plant grows more slowly in shade but still blooms well.

Plant Name: Ceratostigma plumbaginoides

Growing Conditions: Sun or shade and well-drained soil

Size: To 1 foot tall and 2 feet wide

Zones: 5–9

Plant it with: Create a bold display at the end of the season by pairing leadwort with yellow chrysanthemums or white asters.

Bellflower

Often used in cottage gardens, bellflowers produce starry or bell-shaped flowers in blue, violet, pink, or white. Many of the longer-stemmed varieties make excellent cut flowers. Dwarf types, such as ‘Pearl Deep Blue’ work well as groundcovers.

Plant Name: Campanula selections

Growing Conditions: Full sun or part shade and moist, well-drained soil

Size: To 3 feet tall and 2 feet wide, depending on type

Zones: 3-9, depending on type

Plant it with: Bellflowers are perfect companions for blue pincushion flowers (Scabiosa). Bonus: Both are great for cutting.

Buy It: Campanula Carpatica Blue Clips Bellflower ($15, Bluestone Perennials)

Salvia

Both annual and perennial salvia varieties have become garden champions for their heat and drought tolerance, as well as the fact that deer and bunnies tend to leave them alone. For true blue flowers, look for Salvia azurea or S. patens (shown here). Other varieties of salvia, such as ‘May Night’ or ‘Blue Mound’, offer more violet-blue flowers.

Plant Name: Salvia selections

Growing Conditions: Full sun and well-drained soil

Size: To 5 feet tall and wide, depending on type

Zones: 3–9, depending on type

Plant it with: Blue salvia look wonderful with penstemon, a native perennial which is also heat and drought-resistant.

Buy It: Blue Hill Salvia ($28 for five, Breck’s)

Balloon Flower

An easy-to-grow perennial, balloon flower offers puffy, round buds that open to beautiful blue, pink, or white star-shape blooms for several weeks in summer.

Plant Name: Platycodon grandiflorus

Growing Conditions: Full sun and well-drained soil

Size: To 2 feet tall and 1 foot wide

Zones: 4–9

Plant it with: The lilac-pink flowers of ‘Appleblossom’ yarrow (Achillea) or gaura are a perfect complement to blue balloon flowers.

Buy It: Blue Balloon Flower ($24 for two, Breck’s)

Aster

One of the last plants to bloom in many gardens, asters light up the fall landscape and draw pollinators with their starry flowers. These perennials also make long-lasting cut flowers.

Plant Name: Symphyotrichum selections

Growing Conditions: Full sun and well-drained soil

Size: Up to 5 feet tall and 3 feet wide

Zones: 3–9, depending on type

Plant it with: Goldenrod and mums are two perfect partners for blue asters.

Buy It: Marie Ballard Aster ($20, Breck’s)

Morning Glory

Loved by generations of gardeners, morning glory vines come in varieties that offer saucer-shaped, sky-blue flowers. Other varieties bear blooms in bright pink, bold red, purple, white, and even bicolors, such as the blue-and-white ‘Flying Saucers’ variety shown here. This vigorous annual vine is easy to grow from seed and can self-seed prolifically in situations where it’s happy.

Plant Name: Ipomoea tricolor

Growing Conditions: Full sun and well-drained soil

Size: Climbs to 12 feet tall or more

Zones: Annual in 2–8, Perennial in 9–11

Siberian Squill

A good choice for shady gardens, Siberian squill makes a tiny but eye-catching display of bright blue flowers in early spring. These small bulbs will naturalize over time, meaning they’ll slowly spread to create a beautiful blooming carpet.

Plant Name: Scilla siberica

Growing Conditions: Full sun to part shade and well-drained soil

Size: 4-6 inches tall

Zones: 2–8

Plant it with: Contrast blue scilla with pink, yellow, or orange early-flowering species tulips. It also mixes well with other small early bulbs, such as snowdrops.

Buy It: Scilla siberica ‘Spring Beauty’ bulbs ($4 for six, Bluestone Perennials)

Love-in-a-Mist

This annual gets its colorful name from the ferny green leaves that set off the flowers. Love-in-a-mist is easy to grow from seed, and will reseed itself, so you don’t have to keep replanting it. Even after the striking blue petals are gone, the large round seedpods add interest to the garden and vase.

Plant Name: Nigella damascena

Growing Conditions: Full sun to part shade and well-drained soil

Size: up to 2 feet tall

Zones: annual

Plant it with: Try love-in-a-mist with other colorful annuals with contrasting flower shapes, such as celosia and globe amaranth.

Buy It: Jewels Indigo Nigella seeds ($3, Etsy)

Baptisia

The tall blue flower spires of baptisia always make an impressive display, starting in spring and going into summer. The large dark seedpods that follow also look interesting. Also known as false indigo, this bold native perennial is easy to grow because it can tolerant heat and drought well, and deer and other pests don’t bother it.

Plant Name: Baptisia australis

Growing Conditions: Full sun and well-drained soil

Size: 4 feet tall

Zones: 3–8

Plant it with: For a prairie effect, plant baptisia with other natives, such as purple coneflower, milkweed, and switchgrass.

Iris

With myriad types to choose from, irises come in nearly every shade. For the best blue-flowered irises, look for bearded iris, Siberian iris, reticulated iris, and Japanese iris (shown here) varieties.

Plant Name: Iris

Growing Conditions: Full sun and well-drained soil

Size: 6 inches to 3 feet tall, depending on variety

Zones: 4–9

Buy It: Forever Blue Dwarf Reblooming Bearded Iris ($19, Home Depot )

Globe Thistle

The coarsely textured leaves and name of globe thistle may make you think of its weedier relatives, but this pretty perennial is a well-behaved option for your garden. Its long-lasting, steel-blue, spherical blooms appear in summer, and are good cut flowers.

Plant Name: Echinops ritro

Growing Conditions: Full sun and well-drained soil

Size: 1-3 feet tall

Zones: 3–9

Buy It: Globe Thistle Seeds ($9, Etsy)