Hardy Hibiscus, Rose Mallow, Swamp Mallow 'Blue River II'

Hibiscus moscheutos

Family: Malvaceae (mal-VAY-see-ee) (Info)
Genus: Hibiscus (hi-BIS-kus) (Info)
Species: moscheutos (mos-KEW-tos) (Info)
Cultivar: Blue River II
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6-8 ft. (1.8-2.4 m)


36-48 in. (90-120 cm)


USDA Zone 5a: to -28.8 C (-20 F)

USDA Zone 5b: to -26.1 C (-15 F)

USDA Zone 6a: to -23.3 C (-10 F)

USDA Zone 6b: to -20.5 C (-5 F)

USDA Zone 7a: to -17.7 C (0 F)

USDA Zone 7b: to -14.9 C (5 F)

USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

Sun Exposure:

Full Sun

Bloom Color:

White/Near White

Bloom Time:

Mid Summer

Late Summer/Early Fall


Unknown - Tell us

Other details:

Unknown - Tell us

Soil pH requirements:

7.6 to 7.8 (mildly alkaline)

Patent Information:

Unknown - Tell us

Propagation Methods:

From seed; winter sow in vented containers, coldframe or unheated greenhouse

From seed; stratify if sowing indoors

Seed Collecting:

Allow seedheads to dry on plants; remove and collect seeds

Foliage Color:

Unknown - Tell us

Bloom Characteristics:

Unknown - Tell us

Water Requirements:

Requires consistently moist soil; do not let dry out between waterings

Where to Grow:

Unknown - Tell us


This plant has been said to grow in the following regions:

Merritt Island, Florida

Orange Park, Florida

Clarkesville, Georgia

Commerce, Georgia

Marietta, Georgia

Chicago, Illinois

La Grange, Illinois

Plainfield, Illinois

Roscoe, Illinois

Farmersburg, Indiana

Greenville, Indiana

Indianapolis, Indiana

Shawnee Mission, Kansas

Cumberland, Maryland

Randolph, Massachusetts

Battle Creek, Michigan

Mason, Michigan

Cleveland, Mississippi

Franklin, North Carolina

Thackerville, Oklahoma

Bethlehem, Pennsylvania

West Chester, Pennsylvania

North Augusta, South Carolina

Knoxville, Tennessee

Brenham, Texas

Fate, Texas

Liberty Hill, Texas

Richmond, Texas

Temple, Texas

Chesapeake, Virginia

Seattle, Washington

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Gardeners' Notes:


On Jun 30, 2014, Fires_in_motion from Vacherie, LA (Zone 9a) wrote:

Huge, spectacular white flowers, but prone to (seemingly constant) fungal leaf-spotting. Seems weird that a swamp plant would develop fungal problems from too much water... Mine completely died, or so I thought, after the Icepocalypse of 2014. (I live in southeast Louisiana; the temp. got down to about 19.) But now, in early summer, it has sprouted back. I can't say I'm too thrilled about it, but we'll see if it does better this time around. I also found one adorable little seedling a few feet away from it.


On Sep 14, 2007, vossner from Richmond, TX (Zone 9a) wrote:

I like it! bought two on ebay as 4" plants this spring. They are close to 2 ft tall and have had a few blooms. Beautiful, big, all white, and delicate. I look forward to future years when it becomes a fuller plant. Mine are inground, 6-7 hrs of sun.

July 2008. My plants died to the ground but came back in early spring. Shrubs are presently about 4' x 4' and some of the flowers are about 9" in diameter. What a spectacular hardy hibiscus! I read it likes moist environment, but mine is not planted in a particularly wet area. This plant gets A+

June 2014: dead. I think excessive watering


On Nov 9, 2005, rose_mallow from Randolph, MA (Zone 5a) wrote:

When I bought this plant it was dying/liquidated for $3. Hardy hibiscus was unknown to me, all I know is the picture on the container looked beautiful - I put it on the ground beginning of Fall 2004. Summer 2005 I couldn't be outside in the garden - every single passerby wanted to know what it was. "never seen anything like it..." me neither. I had no choice in August to move it I saw that it could be divided - I divided it - I have 3 of them now, plus seeds for Summer 2006.
Even after division they were blooming and seeding.


On Sep 19, 2005, jackieshar from Texas/Okla central border
United States (Zone 7b) wrote:

saucer sized blooms, beautiful pure white.......likes a little moisture in the soil..handles the heat well with a bit of afternoon sun.....blooms now and again thru spring, summer and fall..hardy with a bit of mulch