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Blue flowering perennials by zone: the 20 best

True blue is rare in the plant kingdom. Most flowers marketed as "blue" are violet-blue, lavender, or purple-blue. This guide distinguishes between the two where relevant and focuses on the 20 most reliable blue-to-violet-blue perennials for temperate North American.

By Thomas Joseph Published 2026-06-10 Updated 2026-06-10 10 min read

—- title: "Blue flowering perennials by zone: the 20 best" slug: blue-flowering-perennials hub: plants category: "Plant list" description: "The 20 best blue flowering perennials for temperate gardens — with zones, bloom times, and the distinction between true blue and violet-blue." date: 2026-06-10 updated: 2026-06-10 author: "Thomas A." reading_time: 10 release_after: 2026-09-26 —-

True blue is rare in the plant kingdom. Most flowers marketed as "blue" are violet-blue, lavender, or purple-blue. This guide distinguishes between the two where relevant and focuses on the 20 most reliable blue-to-violet-blue perennials for temperate North American gardens.

I grow several of these in my zone 7a Long Island garden: catmint 'Walker's Low' (which I'd describe as violet-lavender rather than blue), Russian sage (clearly lavender), Siberian iris (blue in the best cultivars), and blue-eyed grass. The genuinely blue plants in my garden are the Siberian iris and certain salvia cultivars.

The 20 best blue and blue-violet perennials

1. Catmint 'Walker's Low' (Nepeta × faassenii 'Walker's Low')

Per Missouri Botanical Garden, catmint 'Walker's Low' is one of the most reliable long-blooming perennials in the temperate garden. Violet-blue flowers from May through June; cut back by half after first bloom for a second flush in August–September.

I grow this along my front border. It needs cutting back after the first bloom wave to look presentable through summer — otherwise the center flops and it becomes messy. After the second cut, it is tidy through fall.

2. Russian sage (Salvia yangii, formerly Perovskia atriplicifolia)

Per Missouri Botanical Garden, Russian sage produces an airy cloud of lavender-blue flowers from July through September on silver-gray stems. It is one of the longest-blooming perennials available for zones 4–9.

Per Penn State Extension, Russian sage should be cut back to 6–8 inches above the woody crown in early spring (not fall) to maintain a compact form.

3. Siberian iris (Iris sibirica)

Genuinely blue cultivars of Siberian iris — 'Caesar's Brother' (deep violet-blue), 'Harpswell Happiness' (medium blue), 'Tropic Night' (dark violet-blue) — are among the truest blues in the perennial garden.

4. Speedwell (Veronica spicata)

Per NC State Extension, Veronica spicata produces dense upright spikes of violet-blue flowers. 'Royal Candles' and 'Blue Charm' are the most reliable cultivars.

5. Blue star (Amsonia hubrichtii)

Per Missouri Botanical Garden, blue star has small, star-shaped pale blue flowers in May and outstanding golden fall foliage. It is a native perennial particularly valuable for its fall color as much as its spring bloom.

6. Salvia 'May Night' (Salvia nemorosa 'Mainacht')

Per Cornell Cooperative Extension, 'May Night' salvia is one of the most reliable perennial salvias for zones 4–8, producing deep violet-blue spikes in May–June with a rebloom in late summer if deadheaded.

7. Blue false indigo (Baptisia australis)

Per Clemson HGIC, blue false indigo is a native perennial with spikes of indigo-blue flowers in May and handsome blue-gray foliage through the season. It is drought-tolerant, long-lived, and deer-resistant.

8. Balloon flower (Platycodon grandiflorus)

Per Penn State Extension, balloon flower produces inflated blue buds that open into star-shaped flowers. 'Sentimental Blue' (compact) and 'Astra Blue' are reliable cultivars.

9. Spike speedwell (Veronica austriaca subsp. teucrium 'Crater Lake Blue')

Per Missouri Botanical Garden, 'Crater Lake Blue' produces intense gentian-blue flower spikes in late spring. It is shorter and earlier-blooming than V. spicata.

10. Geranium 'Rozanne'

Per Rutgers NJAES, Geranium 'Rozanne' is arguably the best blue-flowering perennial geranium, blooming continuously from June through frost.

11. Agastache 'Blue Fortune' (Agastache × 'Blue Fortune')

Per Missouri Botanical Garden, Agastache 'Blue Fortune' produces dense blue-violet spikes highly attractive to bees and hummingbirds. Long blooming; heat and drought tolerant.

12. Borage (Borago officinalis)

While technically an annual/biennial, borage reseeds so freely it functions as a perennial in most gardens. The star-shaped flowers are one of the true blues available.

13. Veronicastrum (Veronicastrum virginicum 'Fascination')

Per NC State Extension, Culver's root produces tall spikes of pale violet-blue flowers in midsummer, attractive to pollinators. More architectural than typical salvias or veronicas.

14. Chicory (Cichorium intybus)

Chicory's roadside flowers are a genuine true blue — one of the truest blues found in flowering plants. As a garden perennial it is weedy but the color is extraordinary on sunny mornings.

15. Salvia patens 'Patio Deep Blue'

Per Cornell Cooperative Extension, Salvia patens is the most reliably true blue annual/tender perennial available in commerce, producing large, rich blue flowers.

16. Delphiniums (blue cultivars)

Per Missouri Botanical Garden, blue delphinium cultivars like 'Blue Jay', 'Blue Bird', and 'Galahad' produce the most dramatic blue flower spikes available in temperate gardens.

17. Bugloss (Anchusa azurea 'Loddon Royalist')

Per Penn State Extension, Anchusa azurea 'Loddon Royalist' produces intense gentian-blue flowers in May–June. Short-lived perennial (2–3 years) but one of the truest blues.

18. Lungwort (Pulmonaria 'Blue Ensign')

Per Missouri Botanical Garden, lungwort thrives in shade and produces blue flowers in early spring — one of the earliest blue bloomers in the shade garden.

19. Blue-eyed grass (Sisyrinchium angustifolium)

A native iris relative, blue-eyed grass produces small but genuine blue flowers on grass-like foliage. Per Oregon State Extension, it self-seeds freely and naturalizes well in meadow settings.

20. Baptisia 'Purple Smoke' (Baptisia australis × alba)

A hybrid false indigo with smoky blue-purple flowers and particularly attractive dark stems.

Frequently asked questions

Is there a true blue rose? No. Per Cornell Cooperative Extension, roses lack the biochemical pathway to produce delphinidin, the pigment responsible for blue flower color. All roses marketed as "blue" are lavender, mauve, or purple. Genetic engineering research into blue roses is ongoing but no commercially available true blue rose exists.

What is the longest-blooming blue perennial? Per Missouri Botanical Garden, Geranium 'Rozanne' has one of the longest bloom seasons of any blue perennial — June through frost in most zones, with minimal deadheading required.

Do blue perennials grow in full shade? Per NC State Extension, most blue perennials require at least partial sun (3–4 hours). Exceptions: lungwort (Pulmonaria spp.) blooms in deep shade; some geraniums tolerate partial shade. Blue hostas provide blue foliage (not flowers) in shade.

Which blue perennials are most drought-tolerant? Per Texas A&M AgriLife Extension, Russian sage, blue false indigo (Baptisia australis), agastache, catmint, and blue-eyed grass are all drought-tolerant once established.

Sources

  1. Missouri Botanical Garden — Perennial Plant Database
  2. NC State Extension — Perennial Flowers
  3. Cornell Cooperative Extension — Perennial Border Design
  4. Penn State Extension — Perennial Flowers
  5. Clemson HGIC — Baptisia
  6. Rutgers NJAES — Geranium 'Rozanne'
  7. Oregon State Extension — Native Perennials
  8. Texas A&M AgriLife Extension — Drought-Tolerant Perennials

Sources

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