You might not realize how uncommon Blue flowers are until you really look for them. A trip to your local plant nursery is likely to end empty-handed (with the exception of a few stalwarts like the mophead hydrangea). But that doesn’t mean blue-flowered shrubs don’t exist.

Blue flowers are exceptionally rare because plants haven’t evolved to produce blue pigments. I’ll go into a bit more detail on that below. The reality is that most Blue Flowers teeter on the edge of purple, only showcasing their blue undertones in the right lighting.

This article highlights the shrubs with blue flowers that do exist and that are readily available to most home gardeners. Keep reading for the best ways to expand your garden’s color palette.

Why Are Blue Flowers So Uncommon?

Plant scientists believe that blue is the rarest color of all when it comes to flowers. Many of the blue flowers we see in day-to-day life are dyed (in the case of bouquets) or edited (in the case of photos). Either way, they definitely aren’t created by Mother Nature.

Natural flower colors are the result of botanical pigments. Anthocyanins are some of the most prevalent pigments in plants and are the chemicals directly responsible for producing blue flowers.

Anthocyanins are normally purple, red, pink, or orange, but some clever plants have figured out how to manipulate these pigments using things like pH to make them appear blue. This also explains why the vast majority of naturally blue flowers appear purple in some light conditions — the pigment’s original color is trying to shine through. 

Types of Shrubs With Blue Flowers

This article isn’t just focused on blue flowers in general, but specifically on shrubs that boast cyan-hued blooms. It might help to define what a shrub is in comparison to other types of plants, so you know exactly what will or will not be featured in the list below.

Annuals

Many of the world’s showiest flowers belong to annuals or very tender perennials. Though short-lived, these plants pack a big punch when it comes to color and overall form.

Since annuals only have a single growing season to mature, they rarely get very big. They are ideal for seasonal containers or filling in small gaps between other plants in the garden.

Herbaceous Perennials

Herbaceous perennials are plants that live for several years but that die back to the ground each winter. The root systems lay dormant beneath the soil and resprout once the growing conditions are once again suitable.

Some herbaceous perennials have clump-like growth habits that resemble shrubs, even though they don’t produce woody growth. I’ll be mentioning a few of these exceptions in the list below since they serve a very similar purpose in terms of landscape design as ‘true’ shrubs.

Shrubs

Though the term is used rather loosely in the gardening world, shrubs are defined as perennials with woody growth and multiple stems coming from the ground. Shrubs are generally smaller than trees.

Shrubs are extremely valuable in landscape design. Their long-lived nature helps anchor the rest of the garden space, which can then be filled with more temporary plants to suit your changing vision. Large shrubs can also be used as privacy hedges and to add structure to an open piece of land.

19 Blue-Flowering Shrubs You Can Grow Today

If you want to add less common colors to your garden design, it helps to know exactly what you’re looking for. It’s not enough to just peruse the stock of your local garden center. (However, many greenhouses will order specific varieties if you ask!)

The plants on this list are definitely some of the best to start with in terms of blue flowers and also tend to be the easiest to find. Be sure to pay attention to key traits like hardiness and bloom time when deciding which varieties are best for you.

1. Nikko Blue Hydrangea

Hydrangea macrophylla ‘Nikko Blue

• Type: Deciduous shrub
• Hardiness: 6 to 9
• Bloom Time: Early summer

Generally considered to be one of the best blue hydrangeas on the market, Nikko Blue is a compact shrub that blooms earlier than many of its counterparts. It is a mophead variety with round, sterile flower clusters that can appear as early as June.

Like all mophead hydrangeas, Nikko Blue will produce the desired color when grown in acidic soil. Soil with a pH above about 5.5 may turn the flowers purple or pink and leaves may turn yellow. 

2. Nantucket Blue Hydrangea

Hydrangea macrophylla ‘Grenan’

• Type: Deciduous shrub
• Hardiness: 6 to 9
• Bloom Time: Summer

Hydrangeas are incredibly popular along New England’s coastline, and this variety is aptly named after Nantucket Island off of Massachusetts. Nantucket Blue produces baby blue flowers when grown in acidic soil.

This is a reblooming mophead hydrangea that will flower on both old and new wood. In other words, flowers will appear even if the previous year’s growth was pruned off or damaged by a harsh winter.

3. Wedgewood Blue Lilac

Syringa vulgaris ‘Wedgewood Blue

• Type: Deciduous shrub
• Hardiness: 3 to 7
• Bloom Time: Late spring

There are a few varieties of common lilac with blue-tinted flowers. Wedgewood Blue is just one example, but it’s also one of the most popular lilac shrubs overall. The flowers tend to fade to purple or magenta as the blooming period comes to a close.

Wedgewood Blue is a late-blooming lilac, so I highly recommend pairing it with other cultivars that flower earlier in the spring. This will prolong the color and fragrance of your spring landscape for several extra weeks (compared to only growing one type of lilac).

4. Trailing Lobelia

Lobelia erinus

• Type: Herbaceous perennial
• Hardiness: 10 to 11
• Bloom Time: Spring to fall

Gardeners in very warm climates can add a pop of blue to their outdoor beds by growing trailing lobelia. This herbaceous perennial is only hardy in Zones 10 and 11 but can be grown as an annual in cooler climates.

Trailing lobelia is generally used as a flowering ground cover or as a ‘spiller’ in seasonal containers. It looks equally lovely in the landscape as it does a window box or terra cotta pot.

5. Lochinch Butterfly Bush

Buddleja davidii x fallowiana ‘Lochinch’

• Type: Deciduous shrub
• Hardiness: 6 to 9
• Bloom Time: Late summer to fall

Lochinch is a very large butterfly bush, growing up to 10 feet tall and across, with flowers that range from light blue to lilac. Each floret is punctuated by an orange center, and the flower spikes are quite fragrant. 

This hybrid starts blooming a bit later than other types of butterfly bushes. However, its flowers will persist until the first frost of the year for many weeks of color.

6. Glass Slippers Butterfly Bush

Buddleja sp. ‘Glass Slippers’

• Type: Deciduous shrub
• Hardiness: 5 to 9
• Bloom Time: Summer to fall

A personal favorite, Glass Slippers is a charming variety of butterfly bushes with periwinkle blossoms. Though not as vibrant as some other varieties, I think it’s a perfect addition to a cottage garden or other relaxed space.

In addition to its blue-tinged flowers, Glass Slippers has unique silvery foliage and stems that contrast nicely against other shrubbery. It has a spreading habit, typically growing nearly twice as wide as it does tall.

7. Woodland Phlox

Phlox divaricata

• Type: Herbaceous perennial
• Hardiness: 3 to 8
• Bloom Time: Spring

Often confused with creeping phlox (P. stolonifera), woodland phlox is a delightful wildflower native to North America. It is a spreading perennial that produces a carpet of periwinkle blooms throughout the spring months.

Unlike other phlox species, woodland phlox doesn’t need full sun to flourish. According to the University of Wisconsin, it will perform best in a location with partial shade and moist soil. It is a wonderful candidate for a narrow border bed, and its diminutive nature won’t compete with more sizable shrubs.

8. Augustine’s Rhododendron

Rhododendron augustinii

• Type: Evergreen shrub
• Hardiness: 6 to 10
• Bloom Time: Early spring

This striking species of rhododendron is sometimes known simply as the ‘blue rhododendron’. Augustine’s rhododendron is an evergreen specimen, so will offer visual interest to the landscape year-round.

Its flowers typically appear as lavender, mauve, or blue-toned periwinkle, with certain cultivars being bred to favor different ends of this color spectrum. A plant profile from Oregon State University even claims that flower color can change slightly from one season to the next on a single shrub.

9. Blue Tit Rhododendron

Rhododendron x ‘Blue Tit’

• Type: Evergreen Shrub
• Hardiness: 6 to 10
• Bloom Time: Spring

Blue Tit is one of the best hybrid rhododendrons for true blue color. This is a dwarf variety of rhododendron, capping out at just 2 to 3 feet tall and wide. It’s ideal for placing at the front of a border bed.

Plant this rhododendron in partial shade for the best results. Its evergreen foliage will add structure and interest to the garden year-round, accented in the spring by its trumpet-shaped flowers.

10. California Lilac

Ceanothus spp.

• Type: Evergreen or deciduous shrub
• Hardiness: 8 to 10
• Bloom Time: Late spring to early summer

Though in no way related to common lilacs in the Syringa genus, it’s easy to see where this flowering shrub got its name. California lilac is native to parts of western North America, delivering a colorful display of fragrant flowers in late spring.

I highly recommend adding California lilac to your garden if your climate is too warm for common lilac to really thrive. The foliage is often evergreen in mild climates, and there are several cultivated varieties to choose from with flowers in assorted shades of blue.

11. Multi Blue Clematis

Clematis x ‘Multi Blue’

• Type: Deciduous vine
• Hardiness: 4 to 11
• Bloom Time: Late spring to fall

On my personal garden wishlist is this blue flowering clematis, a far cry from your grandma’s more traditional purple varieties. Multi Blue is, without a doubt, one of the most popular blue-toned clematis currently on the market.

Multi Blue is a group 2 clematis, meaning that it primarily blooms on old wood. Group 2 varieties don’t require pruning (though a little is 100% okay!). This beauty will reward you by producing flowers in multiple flushes throughout the growing season, attracting pollinators and making it a great companion planting candidate.

12. Blue Ribbons Clematis

Clematis integrifolia ‘Blue Ribbons’

• Type: Herbaceous perennial
• Hardiness: 3 to 9
• Bloom Time: Late spring to summer

Did you know that not all clematis are climbing vines? Blue Ribbons are one such variety that forms a small shrub-like mound about a foot tall. It’s classified as a herbaceous perennial, so new growth emerges fresh from the ground each spring.

The blue flowers are downturned and slightly flared, like the flower caps worn by tiny fairies in illustrated storybooks. Even the seedheads — fluffy, round, and silver — are visually interesting.

13. Azurri Blue Satin Rose of Sharon

Hibiscus syriacus ‘Azurri Blue Satin’

• Type: Deciduous shrub
• Hardiness: 5 to 9
• Bloom Time: Summer

This rose of Sharon is an improved version of the Blue Satin variety previously available. Its flowers are reportedly a much truer blue than seen in the last iteration, with the most striking color being visible just before the buds open.

Azurri Blue Satin is also noteworthy because the flowers don’t produce seeds. This is great news for gardeners who have previously battled a hibiscus self-sowing all over their properties! You can expect hassle-free blooms that last the entirety of summer from this rose of Sharon variety.

14. Blue Chiffon Rose of Sharon

Hibiscus syriacus ‘Blue Chiffon’

• Type: Deciduous shrub
• Hardiness: 5 to 9
• Bloom Time: Late summer to fall

Blue Chiffon is an elegant shrub with densely petaled flowers in shades of lilac and periwinkle. Its relatively late bloom period allows you to extend your garden’s visual beauty with a color not often seen in fall bloomers.

This rose of Sharon has a rounded growth habit and can reach up to 12 feet tall with proper care. Plants grown in cooler climates may experience some winter dieback, which will limit their mature size. As Azurri Blue Satin mentioned just above, this variety produces sterile seeds.

15. Perennial Flax

Linum perenne

• Type: Herbaceous perennial
• Hardiness: 4 to 9
• Bloom Time: Late spring to summer

Perennial flax is one of the best naturally blue flowers. It’s historically been used for industrial purposes, such as making rope, but is now gaining newfound popularity as a garden ornamental thanks to its interesting blooms.

Though not a true shrub, I highly recommend including perennial flax in the foreground of your garden for a pop of unique color. The foliage is semi-evergreen in mild climates and the flowers can bloom for up to three months at a time.

16. Cape Leadwort

Plumbago auriculata

• Type: Evergreen shrub
• Hardiness: 9 to 11
• Bloom Time: Summer to fall

Native to South Africa, cape leadwort is a delicate evergreen shrub with sky-blue flowers very similar to phlox in appearance. In regions like most of the United States, it is most commonly grown as an annual or herbaceous perennial.

Given the chance to mature, cape leadwort will form a beautiful mounded shrub up to 3 feet tall and equally as wide. It can also be trained as a pseudo-vine.

17. Blue Butterfly Bush

Rotheca myricoides

• Type: Evergreen shrub
• Hardiness: 9 to 11
• Bloom Time: Summer

Not to be mistaken for a species of Buddleja, this blue butterfly bush is a semi-tropical evergreen with distinctly shaped flowers. It certainly doesn’t take a genius to figure out where it gets its common name!

Blue butterfly bush is hardy in USDA Zones 9 to 11. However, gardeners slightly further north may be able to grow it as a herbaceous perennial — the stems will die back to the ground each winter but resprout in the spring.

18. Blue Moon Wisteria

Wisteria macrostachya ‘Blue Moon’

• Type: Deciduous vine
• Hardiness: 4 to 9
• Bloom Time: Early summer

Despite its undeniable beauty, Chinese wisteria has largely fallen out of favor due to its incredibly invasive nature. Blue Moon, a variety of Kentucky wisteria, is a viable alternative for many gardeners looking to capture the vintage aesthetic of this flowering vine.

Kentucky wisteria is native to the United States, and generally far less problematic than its Asian cousin. It’s also more cold-tolerant, so gardeners up to Zone 4 can easily grow wisteria outside their own homes.

19. Bluestar

Amsonia tabernaemontana

• Type: Herbaceous perennial
• Hardiness: 3 to 9
• Bloom Time: Late spring

Bluestar is a North American native with pale blue, star-shaped flowers that appear atop erect stems. Though Bluestar is not a shrub, it tends to form mounded clumps that resemble small bushes during the growing season.

This common woodland wildflower will tolerate partial shade, though it tends to look its best when provided with full sun. You can prune back new growth to encourage a shrubbier appearance if desired.

FAQs Blue Flowers

Why aren’t my hydrangea flowers blue?

Mophead hydrangeas respond to soil pH levels. This is what causes some shrubs to have blue flowers while others have pink or purple blooms. Though you can help maintain your hydrangea’s color by acidifying the soil, it’s very hard to grow blue hydrangeas in naturally neutral or alkaline soil long-term.

Citations

• The University of Wisconsin Woodland phlox growing requirements
• Oregon State University Augustine’s rhododendron flower color