It's Mirabilis jalapa - in warmer countries, it does seed itself quite readily. Interesting colour break in the first photo, the yellow/pink streaking.

Thanks so much! Now I can read about it! I have cut it back several times because when it gets a bit taller it hides the water bowl I have for the birds so I can't see it from the house - but it grows back very quicky! Thanks again for your info ... Nina

it produces a tap root a bit like a carrot. in the uk they are usually lifted and kept frost free over the winter. I ve had plain pink and yellow ones for about 5 years now. the flowers open for about 4-6 hrs a day then close up.

Hi Seaburngirl - my friend over here also has them and is also now pleased to know what they are! She said she just cannot get rid of them as they seem to be pretty rampant. I noticed online that they apparantely have a scent when they are open - can't say I've noticed it but I will go an have a closer sniff today! Nina

In milder climates, the roots can get sweet potato size or larger. The scent is usually stronger on white or pale yellow ones, and is most noticeable after dark.

well I cant smell them either. mine are closed at night.