Siberian iris 'Caesar's Brother'
Iris sibirica 'Caesar's Brother' · Iridaceae Popular
Velvety, deep violet-purple flowers, close to black in bud, stand above a sheaf of narrow, grassy leaves. Raised in 1932.
- Size
- 3½ ft tall, 24 in wide
- Zones
- 3 to 8
- Light
- Full sun to part sun
- Flowers
- Late May to late June
- Pets
- Toxic (mild)
- Job in a bed
- Drift
A bed built around Siberian iris 'Caesar's Brother'
The planner designed this bed around Siberian iris 'Caesar's Brother' when this page was made: a 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why Siberian iris 'Caesar's Brother' stands where it does.
The plants
- 1 Siberian iris 'Caesar's Brother' × 3, purple
- 2 Moor grass 'Greenlee' × 5, tan
- 3 Winter heath × 5, pink
- 4 Brown-eyed Susan × 3, yellow
- 5 Silver sage × 1, silver leaves
- 6 Blanket flower 'Burgundy' × 5, red
- 7 Ornamental onion 'Purple Sensation' × 4, purple
- 8 Daffodil × 7, orange
Why this plant
- Nothing here is unique to it. Its leaf, flower shape and colour are all on the plan already. Its case rests on where it stands and when it performs.
Why here
- Anchors a back corner. At 3½ ft it is among the tallest plants 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 blanket flower 'Burgundy' (24 in): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 3 plants in one group. Massed, one kind reads as a single shape. Scattered, it would look spotty.
Why now
- In flower for four weeks. From late May to late June.
- Part of the bed's peak. With moor grass 'Greenlee' and ornamental onion 'Purple Sensation' in late May: 3 kinds at once. No week has more.
Planned as an English border: 4 of the 5 groups (80%) are drifts, longer along the bed than they are deep. Moor grass 'Greenlee', fine in leaf, stands next to bold-leaved silver sage, and each shows the other off. The bed is balanced: the left half carries 50% of the visual weight and the right half 50%.
The planner's own design check: 12 Excellent, 5 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 Siberian iris 'Caesar's Brother' goes in a border
At 3½ ft it belongs in the middle of a bed. In the planner's ten height classes it is moderately tall (3 to 4 ft).
Its job: drift. Planted in a small group of three or five, and repeated further along in the other number.
The most widely grown Siberian iris, and still one of the darkest. After flowering it serves as an upright grass, and the leaves turn gold in autumn.
- Dark purple for early summer
- Grassy foliage all season
- Pond sides and moist borders
What to plant with Siberian iris 'Caesar's Brother'
Plants recorded as good partners for it, and what each pairing does:
- Peony: in flower together for four weeks, from late May.
- Lady's mantle: in flower together for four weeks, from late May; low enough (18 in) to stand in front of it; happy in the same moist soil.
- Blue false indigo: in flower together for three weeks, from late May.
Questions about Siberian iris 'Caesar's Brother'
Does Siberian iris 'Caesar's Brother' need sun or shade?
Siberian iris 'Caesar's Brother' grows in full sun (6 or more hours of direct sun a day) and part sun (4 to 6 hours of sun, including some afternoon sun).
It wants soil that stays evenly moist, of average fertility, and a good soak in dry spells. Once settled in, it stands drought.
What zones does Siberian iris 'Caesar's Brother' grow in?
USDA zones 3 to 8. It is hardy to zone 3, which means it survives winter nights down to about −30 °F (−34 °C).
Above zone 8 it struggles: the zones measure winter cold, but a plant's top zone usually means the summers are too hot or the winters too mild for it to rest.
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does Siberian iris 'Caesar's Brother' flower in my zone?
In zone 5 it flowers late May to late June. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 3 | Mid June to late June |
|---|---|
| Zone 4 | Early June to late June |
| Zone 5 | Late May to late June |
| Zone 6 | Late May to late June |
| Zone 7 | Mid May to mid June |
| Zone 8 | Early May to mid June |
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 Siberian iris 'Caesar's Brother' be planted?
20 in (50 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 3½ ft (100 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many Siberian iris 'Caesar's Brother' plants do I need?
At 20 in apart, set out in staggered rows:
- 4 to fill 10 square feet (about 1 m²)
- 7 for a single row 10 ft (3 m) long
- 14 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as a group of three or five, with a second group further along in the other number.
In the bed above, the planner used three in one group.
Is Siberian iris 'Caesar's Brother' poisonous to dogs and cats?
Yes: mild toxicity to people, dogs, cats and horses. The underground stems (rhizomes) and leaves can cause drooling and stomach upset if eaten.
Rated from NC State Extension and the ASPCA. Where references disagree, the more cautious rating is used.
Is there a pet-safe plant like Siberian iris 'Caesar's Brother'?
These come closest to doing what Siberian iris 'Caesar's Brother' does, and no toxicity is recorded for them:
- Columbine meadow rue: the same job in a bed, the same size and the same flowering time; lavender, pink or white, not purple.
- Bowman's root: the same job in a bed and the same flowering time; 4 in wider, white, not purple.
- Bee balm 'Purple Rooster': the same job in a bed, the same size and the same colour; flowers late June to mid August, medium leaves, not fine.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
Do deer eat Siberian iris 'Caesar's Brother'?
Mostly not. NC State lists it as resistant to deer and rabbits. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.
What flowers after Siberian iris 'Caesar's Brother'?
Siberian iris 'Caesar's Brother' is over by late June. These start as it finishes and carry the same spot on, so it never goes flat:
- Daylily: from late June to early August, 2½ ft tall, to stand in front of it and cover its fading stems.
- Bee balm: from early July to early August, 3 ft tall.
- Black-eyed Susan: from mid July to mid September, 24 in tall, to stand in front of it and cover its fading stems.
What does Siberian iris 'Caesar's Brother' look like in winter?
Siberian iris 'Caesar's Brother' 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 Siberian iris 'Caesar's Brother' good for bees and butterflies?
Siberian iris 'Caesar's Brother' is visited by pollinators, bees and butterflies.
More Iris
- Bearded iris Iris x germanica
- Bearded iris 'Immortality' Iris 'Immortality'
- Blackberry lily Iris domestica
- Blue flag iris Iris versicolor
- Dutch iris Iris x hollandica
- Dwarf bearded iris Iris pumila
- Dwarf crested iris Iris cristata
- Iris 'Katharine Hodgkin' Iris 'Katharine Hodgkin'
- Japanese iris Iris ensata
- Louisiana iris Iris (Louisiana hybrids)
- Netted iris Iris reticulata
- Roof iris Iris tectorum
- Siberian iris Iris sibirica
- Southern blue flag Iris virginica
- Sweet iris 'Variegata' Iris pallida 'Variegata'
- Variegated Japanese iris Iris ensata 'Variegata'
- Yellow flag iris Iris pseudacorus
In these guides
- Plants for wet soil and rain gardens
- Plants that grow near black walnut
- Deer-resistant perennials for full sun
- Rabbit-resistant plants
- Drought-tolerant perennials for full sun
- Garden plants toxic to cats
- Garden plants toxic to dogs
- Plants for butterflies
- Plants for bees
Zone guides: Zone 3 · Zone 4 · Zone 5 · Zone 6 · Zone 7 · Zone 8
Every fact on record
- Type
- Perennial
- Size
- 3½ ft (100 cm) tall, 24 in (60 cm) wide
- Plant
- 20 in (50 cm) apart
- Height class
- Moderately tall (3 to 4 ft)
- Place in the bed
- Middle
- Flowers
- Late May to late June; purple
- Leaves
- Fine texture, herbaceous; green
- Shape
- Upright, clumping
- Hardy in
- USDA zones 3 to 8
- Light
- Full sun, part sun
- Soil
- Average, evenly moist
- Water
- Moderate
- Feeding
- Light, in spring
- Family
- Iridaceae
- Comes from
- Hybrid of two Asian species
- Attracts
- Pollinators, bees, butterflies
- Stands up to
- Deer, rabbits, drought, wet soil, poor soil, black walnut
Checked against NC State Extension, ASPCA poison lists and VASCAN (plants of Canada). 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.