PlantFiles: Flower Of An Hour, Venice Mallow
Hibiscus trionum

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.

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

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!

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.

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.)

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.

I'm with JEFE. I had never seen this plant until after we had our sewer line put in and they came on us like stink on crap. 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 Weedalert.com.
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.

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.