Photo by Melody

PlantFiles: Flower Of An Hour, Venice Mallow
Hibiscus trionum

Family: Malvaceae (mal-VAY-see-ee) (Info)
Genus: Hibiscus (hi-BIS-kus) (Info)
Species: trionum (try-OH-num) (Info)

» View all varieties of Hibiscus

2 vendors have this plant for sale.

17 members have or want this plant for trade.

24-36 in. (60-90 cm)

12-15 in. (30-38 cm)
15-18 in. (38-45 cm)
18-24 in. (45-60 cm)

Not Applicable

Sun Exposure:
Full Sun

Bloom Color:
Scarlet (Dark Red)
Bright Yellow

Bloom Time:
Mid Summer
Late Summer/Early Fall
Mid Fall


Other details:
May be a noxious weed or invasive
Average Water Needs; Water regularly; do not overwater
Self-sows freely; deadhead if you do not want volunteer seedlings next season

Soil pH requirements:
6.1 to 6.5 (mildly acidic)
6.6 to 7.5 (neutral)
7.6 to 7.8 (mildly alkaline)

Patent Information:

Propagation Methods:
From seed; sow indoors before last frost
From seed; direct sow after last frost

Seed Collecting:
Allow seedheads to dry on plants; remove and collect seeds
Properly cleaned, seed can be successfully stored

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By Badseed
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By arsenic
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There are a total of 35 photos.
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6 positives
3 neutrals
6 negatives

Gardeners' Notes:

Neutral jillwozhere On Mar 9, 2014, jillwozhere from Perth
Australia wrote:

I live near Perth Australia and I just noticed this plant in my veggie garden yesterday. I didn't recognise the leaves and decided to wait for the flower. I didn't have to wait long, as it flowered the very next day! Still I did not know this plant, so searched for it online by description. At first I was quite delighted by this pretty little flower, but now I have to be worried as it sounds like hard work if I keep it. I guess I'll have to pull it out. I wonder where the seed came from? Years ago I added soil mix to the yard, but since have been using my home made compost. I did add some bentonite clay last year, but previous to the veggie garden the area was just lawn. I've lived on my rural property for 30 years and never seen this flower until today... pity it goes crazy.

Neutral sharilynncammac On Jul 18, 2013, sharilynncammac from Buhl, ID wrote:

hmmmmm, not sure-pretty little wildflower or evil multiplying weed. I just don't know what to do next with mine. In Buhl, Idaho.

Positive JDahmer2 On Sep 23, 2012, JDahmer2 from Waltham, MA wrote:

I found the Flower of the Hour, or Venice Flower at our job site in Wayland, Massachusetts. I think that it is a neat flower. Never seen one before. I dug it up, just in time. The concrete truck dumped it's excess of concrete in the spot this plant was growing in. I have it on my balcony.

Positive Jaketheplantman On Sep 10, 2009, Jaketheplantman from Dover, PA wrote:

I just found this plant growing near one of my flower Garden's. At first i thought it was a Mallow Musk because of the leave's. I Transplanted it in a pot and move it to my Green House. One day it flowered and was surpise. The plant wasn't a Mallow Musk but a Flower of and Hour. Now i readed other People's Opinion about the plant and they call it a weed and i know this plant will spread by seed. But if you take the time to cut the spent flower heads it can't spread. And doesn't a Columbine do the same if you leave the flower heads on. So really I think its a neat plant to add with the rest of my Garden and to the Mallow Family Plants like Rose Mallow, Large Mallow, HollyHocks and Marsh Mallow. All i also have seeds that i collected form another plant that i found Transplanted in my garden

Negative quasymoto On Jun 29, 2009, quasymoto from Bloomfield, IA (Zone 5b) wrote:

As an avid gardener (veggies and flowers) I have fought for years to YANK these out of my gardens where my veggies grow. I guess I never notice it anywhere else in the yard and or flower gardens. But this can and will take over, but a good tiller w/plenty of horse power keeps the buggers from even getting more than a few leaves on.

The pictures on here are far more prettier than in person, and I never took much notice of how long the bloom was for. I just know it preferred to grow where I didn't want it.

Quasy in S.E. Iowa

Neutral ChemicalFlux On Sep 29, 2008, ChemicalFlux from Minneapolis, MN wrote:

I have never seen this plant before this summer. We brought home a truck-load of dirt to do some landscaping and I believe that this seed was brought to our yard through the black dirt we laid. It has only started to grow where we laid the new dirt.

Before they started to bloom, I was pulling them out of the yard but I got a little behind on the weeding and found a few flowering one morning. I had no idea what they were but I thought they were pretty so I left them. They bloom in the morning hours at different times, it seems it is dependent upon how much light is hitting them - all of them are closed by noon.

I am planning on making a native species wildflower garden in the spring so I am going to leave a few of them but just control their growth by pulling up the new plants. I think as long as I mix longer blooming flowers that grow at the same height - the weedy look they get after the flowers close will not be a large issue.

Thanks for all the other opinions!

Negative CountryGardens On Jun 22, 2008, CountryGardens from Lewisville, MN (Zone 4a) wrote:

I can't believe this weed is even listed here. It is terrible! The only good is when soybean aphids arrive, it is the first plant they attack. Then when you are pulling them, you get nice sticky goo all over you!

It will chock out your good plants.

Negative Equilibrium On Jan 28, 2006, Equilibrium wrote:

Indigenous to Europe, Flower Of An Hour loves disturbed areas and flourishes in them. This plant will probably end up on noxious weed lists sooner or later at the rate I'm seeing them pop up here there and everywhere. The flowers aren't even that showy and they aren't open all that long. Perhaps around a half hour early in the morning and after that all you get to see is scraggly foliage sprawled out over the ground. Good thing is that it is an annual so if you keep pulling it up, sooner or later you'll beat back the seed bank.

Negative aasplus On Oct 30, 2005, aasplus from Lordstown, OH (Zone 5a) wrote:

I'm with JEFE. I had never seen this plant until after we had our sewer line put in. I must admit I think the flower is beautiful, I have seen many of them bloom, each time I made a mental note and tried to find out what it was. After 4 years I found it on the internet with many warnings, it is an invasive weed. The seeds came be dormant for 50 years the are where these started to grow had not been touched in 23 years so crunch those numbers. All it took was the rain and a little sun and they invaded like Atilla the Hun. I just found out they were a weed today but I sort of knew that several years ago when they came out like gangbusters. The flowers bloom quickly but the seeds grow and spread quicker. The name is Venice Mallow (Flower of an hour) (Hibiscus trionum) I found the info on
This plant needs to be tacked up on the Post Office Bulletin Board. Another good thing I can say on the plants behalf is, the tap root is easy to pull out. I'm sorry to burst your bubble about this pretty little flower but I like to personally choose the plants for my flower beds, I must admit I let a few grow but when I couldn't keep up with the seed production I started the evacuation process which is still going on after 4 years.
I feel better now. Thanks for the chance to get that off my chest.

Positive jansong On Sep 6, 2005, jansong from South Hadley, MA (Zone 5b) wrote:

One plant came up in my garden outside of Philadelphia, PA this summer and it has taken weeks for me to identify it. Maybe it will become the invasive problem that others write about, but this beautiful flower is a joy the few hours it comes out.

Negative JefeQuicktech On Dec 30, 2004, JefeQuicktech from Moorhead, MN (Zone 4a) wrote:

I have a tough time considering Canada Thistle as a weed. However, Flower Of An Hour, Venice Mallow Hibiscus trionum is a WEED. It is not just invasive in our garden it is EVIL, bad, malo, muy malo, inicuo.

Before I identified this weed and knew what it was, I have literally checked every half hour looking for blooms. Thinking it was some really cool, rare plant. Oh! You Venitian Vixen you fooled me. Flower of an hour? Try flower of a second! Some days it never bloomed.

Kill them early and kill them often would be my suggestion. When you think of this plant, think INVASIVE, such as in "Invasion of the Body Snatchers".

(Sorry for the SHOUTING. I am just trying to warn you.)

Positive DiOhio On Jun 25, 2004, DiOhio from Corning, OH (Zone 6a) wrote:

I love this flower. We have it wild here in SE Ohio. One year it came up in one of my flowerbeds and I've left it reseed year after year.

Positive nansgarden2 On Apr 5, 2004, nansgarden2 from Silt, CO (Zone 4a) wrote:

Bladder Hibiscus or Flower of the Hour.
Found in Asia Africa and all Australia.
Good bedding plant slightly upright trailing habit.
I purchased a single 3" potted plant from an organic herb farm over 4 years ago . The sales lady told me it would probably only survive as an annal.This annual-biennial is very hardy, tolerates dry heat. Self sows and can become invasive if you do not remove seed pods and or new seedlings in your garden.
They are the most beautiful flower, Creamy petals with an almost black/violet center.
It will take your breath away!

Positive henkmaters2 On Sep 3, 2003, henkmaters2 wrote:

We bought seeds for this plant in New Zealand and it has grown over two meters high! As of September 2003, it's still pushing and flowering.
Henk Maters

Negative lupinelover On Jul 20, 2002, lupinelover from Grove City, OH (Zone 6a) wrote:

Plant self-sows prodigously and apparently the seeds can survive in the ground for many years, waiting for the correct conditions to germinate.

Flowers only remain open for a few minutes, closing as soon as clouds or shade strike them.


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

Atwater, California
Fairfield, California
Merced, California
San Jose, California
Stockton, California
Canon City, Colorado
Denver, Colorado
Rifle, Colorado
Dunnellon, Florida
Demorest, Georgia
Buhl, Idaho
Hinsdale, Illinois
Kansas, Illinois
Westchester, Illinois
Flora, Indiana
Bloomfield, Iowa
Nichols, Iowa
Barbourville, Kentucky
Ewing, Kentucky
Frederick, Maryland
Bridgewater, Massachusetts
Waltham, Massachusetts
Erie, Michigan
Lewisville, Minnesota
Minneapolis, Minnesota
Belton, Missouri
Neosho, Missouri
Cincinnati, Ohio
Columbia Station, Ohio
Fremont, Ohio
Glouster, Ohio
Lynchburg, Ohio
Portland, Oregon
Salem, Oregon
Allentown, Pennsylvania
Dover, Pennsylvania
Newtown Square, Pennsylvania
Pottstown, Pennsylvania
Schnecksville, Pennsylvania
Mc Kinney, Texas
Zapata, Texas
Earlysville, Virginia
Muscoda, Wisconsin
South Milwaukee, Wisconsin

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