Lin, you're welcome. First though, check your entries for P. oleracea as they look to have opposite leaves. According to the site I linked to above, P. oleracea has alternate leaves which would seem to be correct.
http://www.flowersofindia.net/...
However, this edu. site gives a good description and it says it has both alternate and opposite. It also says the flowers are yellow, different colours are likely to be varieties.
http://www.ppws.vt.edu/scott/w...
