Best Blue Flowers for Your Garden

A big, sky blue hydrangea is absolutely breathtaking. Get your bigleaf hydrangeas to go blue by increasing the acidity of the soil. Adding soil sulfur is one way to do this.

Here's a hint: Bigleaf hydrangeas can be shy bloomers. Most bloom on last-year's growth, so if you need to prune them, do so right after they finish flowering.

Name: Hydrangea macrophylla

Growing Conditions: Part shade and moist, well-drained soil. Don't let bigleaf hydrangeas get too dry.

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

Zones: 6-9

Grow it with: Blue bigleaf hydrangeas look stunning when paired with white varieties such as Annabelle hydrangea or oakleaf hydrangea.

There are lots of garden-worthy perennial geraniums, but 'Rozanne' is one of the best. This top-notch perennial blooms from June to frost, producing a nearly endless supply of sky blue flowers.

Plant Name: Geranium 'Rozanne'

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

Size: To 2 feet tall and 3 feet wide

Zones: 4-8

Plant it with: Because the geranium starts in early summer, pair it with spring-blooming bulbs such as grape hyacinth, blue crocus, and white daffodils.

Delphiniums offer some of the truest-blue shades in the garden. In many areas, the plants are a bit fussy -- though many gardeners find these regal flowers well worth the extra effort.

Here's a hint: Stake taller delphinium varieties to keep them from toppling over in the wind. Grow them in a soil that's rich in organic matter or fertilize them in poor soil to keep them looking their best.

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

Grow it with: Dwarf delphiniums such as 'Butterfly Blue' or 'Summer Nights' look great with Coreopsis 'Moonbeam' or Gaillardia 'Fanfare'

A gorgeous but underused shade-garden plant, brunnera produces sprays of sky blue flowers in spring.

Here's a hint: The heart-shaped leaves are rather plain, so look for variegated selections, such as the one shown here, to increase the season of interest.

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 blooms look fantastic paired with white or yellow daffodils.

A beautiful spring-flowering bulb, grape hyacinths produce clusters of blue, purple, white, or yellow flowers in midspring.

Plant Name: Muscari selections

Growing Conditions: Sun or shade and well-drained soil

Size: 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 them with crocus and summer-blooming perennials such as columbine.

Clematis bloom in a range of color, but the true blues such as 'Crystal Fountain' (shown here), 'Ice Blue', or 'Arabella' are some of the most charming. Grow these vines on a trellis or in a small tree or large shrub.

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

Grow it with: A classic way to grow clematis is to combine them with climbing roses. Create contrast with a yellow rose such as 'Graham Thomas Climbing' or a white type such as 'Climbing Iceberg'.

A great plant you've probably never heard of, bluestar deserves a lot more attention. It produces clusters of clear blue flowers in late spring. It's also heat, drought, deer, and rabbit resistant. Plus, 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.

Lead plant is an aggressively spreading ground cover that puts on a show at the end of the season with its sky blue flowers and rich red fall foliage.

Here's a hint: Lead 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, end-of-the-season display by pairing lead plant with yellow chrysanthemums.

Bellflowers are charming plants often used in cottage gardens. Most have starry or bell-shaped flowers in shades of white, blue, violet, and pink. Many of the longer-stemmed varieties are great cut flowers. Dwarf types, such as the 'Pearl Deep Blue', shown here, are good ground covers.

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 prefect companions for pincushion flowers (Scabiosa) and both are great for cutting.

Salvia varieties have become garden champions for their heat and drought resistance, as well as the fact that even hungry deer and bunnies tend to leave them alone.

For true blues, look for Salvia azurea or S. patens. Other types, such as 'May Night' or 'Blue Mound' are more violet blue.

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

Grow it with: Blue salvias look wonderful with penstemon varieties, which are also heat and drought resistant.

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

Plant Name: Platycodon grandiflorus

Plant Name: Full sun and well-drained soil

Size: To 2 feet tall and 1 foot wide

Zones: 4-9

Grow it with: The lilac-pink flowers of 'Appleblossom' yarrow (Achillea) or gaura are a perfect complement to balloon flower.

Asters are one of the last plants to bloom in many gardens. Enjoy their blue, purple, pink, white, or red flowers in the garden or as long-lasting cut flowers.

Plant Name: Aster selections

Growing Conditions: Full sun and well-drained soil

Size: 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 aster.

Loved by generations of gardeners, morning glories offer saucer-shaped sky blue flowers. This vigorous vine is easy to grow from seed.

Here's a hint: Morning glories can take a couple of months to start flowering after you plant the seeds. Make sure they're in full sun and don't fertilize them too much to get them to flower faster.

Plant Name: Ipomoea tricolor

Growing Conditions: Full sun and well-drained soil

Size: Climbs to 12 feet tall or more

Zones: Annual

Grow it with: Blue and yellow are a no-fail combination, so try yellow black-eyed Susan vine (Thunbergia alata) or yellow Spanish flag (Ipomoea lobata).