These were growing between the sidewalk and the street in a neighbourhood in Honolulu. Weed1 has pretty red flowers about 1cm across. Weed2 is at the upper left. Weed2 is just slightly larger. This one is Asteraceae; I'm not sure about the other one.
The red one is an Emilia sp. (Asteraceae) The second one has the general appearance of Tridax procumbens to me (with a slight mutation causing it to produce more ray flowers than in general).
Thank you, Axel. It seems we can narrow down the species: Of the four Emilia species reported in Hawaii, only E. javanica (Burm.) Rob. and E. sonchifolia (L.) DC were found on the islands of Oahu and Kauai, while on Lanai only the Red and Orange types of E. javanica were observed. From Weed ecology and economic importance of Emilia javanica (Burm.) Rob. and E. sonchifolia (L.) DC (1975).Of the two, only E. javanica is red (the other is lilac-coloured). The Smithsonian Flora of the Hawaiian Islands page shows it as naturalized, with Synonyms: Cacalia coccinea Sims, Cacalia sagittata Willd., Emilia flammea Cass., Emilia sagittata (Willd.) DC. From that page, the links on the name go to good descriptions. Common name Coat Buttons. Cute. I posted the flower I got in focus and it happened to have a complete set of ray flowers, but most of them did not have so many. I was starting to wonder if they didn't ever have a complete set.
