Louisiana iris
Iris (Louisiana hybrids) · Iridaceae
Flat, wide-petalled flowers in the widest colour range of any iris, including true red, on plants bred from the swamp irises of the Gulf Coast.
- Size
- 3 ft tall, 24 in wide
- Zones
- 5 to 9
- Light
- Full sun to part sun
- Flowers
- Mid May to early June
- Pets
- Toxic (mild)
- Job in a bed
- Accent
A bed built around Louisiana iris
The planner designed this bed around Louisiana iris 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 251 that suit those conditions and its wet soil, and says below why Louisiana iris stands where it does.
The plants
- 1 Louisiana iris × 4, purple
- 2 Himalayan fleeceflower 'Darjeeling Red' × 3, pink
- 3 Mouse-ear coreopsis 'Nana' × 24, yellow
- 4 Swamp milkweed 'Ice Ballet' × 3, white
- 5 Inkberry 'Gem Box' × 1, dark green leaves
- 6 Gray's sedge × 3, green
- 7 Snowdrop × 5, white
Why this plant
- The only purple.
Why here
- Anchors a back corner. At 3 ft it is one of the taller 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 swamp milkweed 'Ice Ballet' (3½ ft) and inkberry 'Gem Box' (2½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 4 plants in 2 places. An accent is a punctuation mark: the repeat along the bed gives it rhythm.
Why now
- In flower for four weeks. From mid May to early June.
- Part of the bed's peak. With mouse-ear coreopsis 'Nana' and Gray's sedge in late May: 3 kinds at once. No week has more.
Planned as an English border: 6 of the 7 groups (86%) are drifts, longer along the bed than they are deep. Mouse-ear coreopsis 'Nana' and Himalayan fleeceflower 'Darjeeling Red' finish the front edge. The flowering is at its height from late May, with 3 kinds out together.
The planner's own design check: 11 Excellent, 5 Good, 1 Satisfactory. 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 Louisiana iris goes in a border
At 3 ft it belongs in the middle of a bed. In the planner's ten height classes it is medium tall (2½ to 3 ft).
Its job: accent. An upright plant used singly, like a punctuation mark, and repeated at intervals to give the bed rhythm.
Where bearded irises rot in southern heat and humidity, these thrive. They want acid soil, sun and moisture, and will grow in shallow water.
- Wet soil and pond margins in warm regions
- Rain gardens
- Irises for the hot, humid South
What to plant with Louisiana iris
Plants recorded as good partners for it, and what each pairing does:
- Swamp milkweed: takes over when it finishes, flowering from early July.
- Cardinal flower: carries the spot on into mid September; happy in the same wet soil.
- Hardy hibiscus: carries the spot on into mid September; bold leaves against its medium ones; tall enough (5 ft) to stand behind it.
Questions about Louisiana iris
Does Louisiana iris need sun or shade?
Louisiana iris 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 moist to wet soil, rich in organic matter, and plenty of water.
What zones does Louisiana iris 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 Louisiana iris flower in my zone?
In zone 5 it flowers mid May to early June. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 5 | Mid May to early June |
|---|---|
| Zone 6 | Early May to early June |
| Zone 7 | Early May to late May |
| Zone 8 | Late April to late May |
| Zone 9 | Mid April to late May |
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 Louisiana iris 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 3 ft (90 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many Louisiana iris 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, repeated along the bed at intervals; a slender one reads better as a clump of three.
In the bed above, the planner used four in two groups.
Is Louisiana iris 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 the ASPCA. Where references disagree, the more cautious rating is used.
What flowers after Louisiana iris?
Louisiana iris is over by early June. These start as it finishes and carry the same spot on, so it never goes flat:
- Swamp milkweed: from early July to early August, 4 ft tall (a recorded partner).
- Daylily: from late June to early August, 2½ ft tall.
- Yarrow: from mid June to late August, 24 in tall, to stand in front of it and cover its fading stems.
What does Louisiana iris look like in winter?
Louisiana iris holds some of its leaves into winter, more in a mild year or a sheltered spot, and they look tired by March. Cut the old ones off as new growth starts.
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
- Netted iris Iris reticulata
- Roof iris Iris tectorum
- Siberian iris Iris sibirica
- Siberian iris 'Caesar's Brother' Iris sibirica 'Caesar's Brother'
- 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
- Garden plants toxic to cats
- Garden plants toxic to dogs
- Plants with blue flowers
- Plants for a white garden
Every fact on record
- Type
- Perennial
- Size
- 3 ft (90 cm) tall, 24 in (60 cm) wide
- Plant
- 18 in (45 cm) apart
- Height class
- Medium tall (2½ to 3 ft)
- Place in the bed
- Middle
- Flowers
- Mid May to early June; purple, blue, red, yellow, white
- Leaves
- Medium texture, semi-evergreen; green
- Shape
- Upright, spreading
- Hardy in
- USDA zones 5 to 9
- Light
- Full sun, part sun
- Soil
- Rich, moist to wet
- Water
- High
- Feeding
- Moderate, in spring
- Family
- Iridaceae
Checked against ASPCA poison lists. 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.