Blue sage
Salvia azurea · Lamiaceae
True sky-blue flowers on tall, thin, wand-like stems in early autumn. A prairie native that leans on its neighbours.
- Size
- 4 ft tall, 24 in wide
- Zones
- 5 to 9
- Light
- Full sun
- Flowers
- Late August to mid October
- Pets
- No toxicity recorded
- Job in a bed
- Weaver
A bed built around blue sage
The planner designed this bed around blue sage when this page was made: a 12 × 6 ft (3.7 × 1.8 m) cottage garden in zone 6, full sun. It chose the other plants from the 715 that suit those conditions and its dry soil, and says below why blue sage stands where it does.
The plants
- 1 Blue sage × 3, blue
- 2 Cheddar pinks 'Firewitch' × 14, pink
- 3 Sea thrift × 8, white
- 4 False sunflower 'Summer Sun' × 3, yellow
- 5 Silver sage × 1, silver leaves
- 6 Sideoats grama × 3, purple
- 7 Star of Persia × 5, purple
- 8 Schubert's allium × 4, pink
Why this plant
- The only spires. The others are globes, daisies and airy sprays. Shape reads at a distance, where colours blur.
- The only blue.
Why here
- Anchors a back corner. At 4 ft it is the tallest plant here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to sideoats grama (2½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 3 plants in one clump. A single spire is too slight to hold a place alone, so here the accent is a clump.
Why now
- In flower for 8 weeks. From late August to mid October.
- Closes the season. For its last five weeks nothing else on the plan is in flower.
Planned as a cottage garden: 32 of the 32 plants (100%), bulbs aside, stand alone or in groups of no more than five, small enough for the kinds to mingle. The flowering year starts with sea thrift in early May and ends with blue sage in mid October. Cool colours (blue, pink and purple) with yellow as the warm note, and white to calm things between them.
The planner's own design check: 11 Excellent, 6 Good. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where blue sage goes in a border
At 4 ft it belongs at the back of a bed. In the planner's ten height classes it is moderately tall (3 to 4 ft). It is airy enough to see through, so it can also come forward and veil what is behind it.
Its job: weaver. A light, airy plant threaded singly between sturdier ones to knit the planting together.
The clearest blue of the late season, and perfect with goldenrod and tawny grasses. It flops on its own, so cut it back by half in June or grow it through grasses.
- Sky blue for autumn
- Prairie planting with grasses
- Dry soil
What to plant with blue sage
Plants recorded as good partners for it, and what each pairing does:
- Little bluestem: its blue-green leaves are a setting for the flowers, before and after; happy in the same dry soil.
- Switchgrass 'Shenandoah': its green leaves are a setting for the flowers, before and after.
- Goldenrod 'Fireworks': blue against yellow, opposite each other on the colour wheel, in flower together for seven weeks.
Questions about blue sage
Does blue sage need sun or shade?
Blue sage grows in full sun (6 or more hours of direct sun a day).
It wants dry, sharply drained soil, on the lean side, with no feeding, and little watering once settled. Once settled in, it stands drought.
What zones does blue sage grow in?
USDA zones 5 to 9. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does blue sage flower in my zone?
In zone 5 it flowers late August to mid October. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 5 | Late August to mid October |
|---|---|
| Zone 6 | Late August to mid October |
| Zone 7 | Mid August to mid October |
| Zone 8 | Mid August to mid October |
| Zone 9 | Early August to mid October |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should blue sage be planted?
18 in (45 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 24 in (60 cm), so a group knits into one patch.
It grows 4 ft (120 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many blue sage plants do I need?
At 18 in apart, set out in staggered rows:
- 5 to fill 10 square feet (about 1 m²)
- 7 for a single row 10 ft (3 m) long
- 17 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as one at a time, threaded between sturdier plants.
In the bed above, the planner used three in one group.
Is blue sage poisonous to dogs and cats?
No toxicity is recorded for dogs, cats, horses or people, according to NC State Extension.
"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.
Do deer eat blue sage?
Mostly not. NC State lists it as resistant to deer. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.
What flowers after blue sage?
Blue sage is over by mid October. These start as it finishes and carry the same spot on, so it never goes flat:
- Tatarian aster 'Jindai': from early October to early November, 4 ft tall.
- Japanese onion 'Ozawa': from early October to early November, 10 in tall, to stand in front of it and cover its fading stems.
- Bodnant viburnum 'Dawn': from early November to late December, 10 ft tall.
What does blue sage look like in winter?
Blue sage dies down to the ground and there is nothing to see until spring. The old stems can be cut in autumn, or left until spring as shelter for overwintering insects.
Is blue sage good for bees and butterflies?
Blue sage is visited by pollinators, bees and butterflies.
It is native to the United States.
More Salvia
- Anise sage 'Black and Blue' Salvia guaranitica 'Black and Blue'
- Autumn sage Salvia greggii
- Bog sage Salvia uliginosa
- Clary sage Salvia sclarea
- Culinary sage Salvia officinalis
- Meadow sage Salvia nemorosa
- Meadow sage 'Caradonna' Salvia nemorosa 'Caradonna'
- Mexican bush sage Salvia leucantha
- Rosemary Salvia rosmarinus
- Russian sage Salvia yangii (formerly Perovskia)
- Russian sage 'Little Spire' Salvia yangii 'Little Spire'
- Salvia 'Hot Lips' Salvia microphylla 'Hot Lips'
- Salvia 'May Night' Salvia nemorosa 'Mainacht'
- Silver sage Salvia argentea
- Whorled sage 'Purple Rain' Salvia verticillata 'Purple Rain'
- Wood sage 'Blue Hill' Salvia x sylvestris 'Blauhügel'
- Wood sage 'East Friesland' Salvia nemorosa 'Ostfriesland'
In these guides
- Deer-resistant perennials for full sun
- Drought-tolerant perennials for full sun
- Pet-safe plants for a sunny border
- Native perennials for pollinators
- Plants for butterflies
- Plants for bees
- Tall perennials and grasses for the back of a border
- Plants with spires: vertical accents
- Plants that flower in fall
- Plants with blue flowers
- Silver and grey-leaved plants
Every fact on record
- Type
- Perennial
- Size
- 4 ft (120 cm) tall, 24 in (60 cm) wide
- Plant
- 18 in (45 cm) apart
- Height class
- Moderately tall (3 to 4 ft)
- Place in the bed
- Back, or further forward: it is airy enough to see through
- Flowers
- Late August to mid October; upright spires; blue
- Leaves
- Fine texture, herbaceous; grey-green
- Shape
- Upright, clumping
- Hardy in
- USDA zones 5 to 9
- Light
- Full sun
- Soil
- Lean, dry and sharply drained
- Water
- Low
- Feeding
- None needed
- Family
- Lamiaceae
- Comes from
- South and Central U.S.A
- Attracts
- Pollinators, bees, butterflies
- Stands up to
- Deer, drought
Checked against NC State Extension. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.