It's a sun loving plant which can't take cold temperatures, and is therefore often grown as an annual. However, although it will die down in the autumn, the tubers can be lifted and stored, much like dahlias, or if it's not too cold just left where they are. This year I grew some plants from last year's tubers and others from seed, starting both off at about the same time. The tubers have come on far faster and are now in flower, while the others are still fairly small. If you do plant from seed, try soaking the seeds for a day or so before you put them in. They germinate far faster.
The plants grow to about 3ft, and don't seem to have any particular requirements as far as soil is concerned, though one site I found suggested they like slightly alkaline conditions. That would explain why they do so well for me, as the water here is very hard, and I have problems with lime-hating plants. They need a lot of water, and wilt immediately if they get dry. However, despite looking very dramatic, they do pick up again well once they've had a good soak.
The plants put out copious quantities of flowers, which can have a wide range of colours and are sometimes variegated. They're set off well by the bright green leaves which are half the attraction of the plant. The flowers are well known for the fact that they don't open till the evening - hence many of their names - but the other intriguing thing about them is that they will often put out different coloured flowers on the same plant. It hasn't happened yet this year, but here's a photo of one I had two years ago.
The flowers only last a day, but are replaced by others immediately. Large seeds then form, at first greeny yellow but maturing to black, again providing an attractive contrast with the foliage.
In a garden the plant will happily self seed, but if you don't want it to it's easy to collect the seeds for storage (if time consuming because of the quantities). If you have small children around, however, beware. The seeds, which look temptingly like little sweets, are poisonous - as are other parts of the plant.
Being poisonous hasn't stopped it having a long history as a medicinal plant however, as it also has antifungal and antiviral properties (don't try this at home). Various chemical compounds extracted from the plant are now used commercially as the basis of products combatting viruses in crops such as corn and potatoes.
This probably explains why they are one of the few plants that I've never seen affected by pests and diseases. While all else is succumbing to the red spider mite or powdery mildew, the Four o'clocks plough on bright and healthy. Which for me guarantees their place on the balcony any year.
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