Determining which flowers are native to the Caribbean is a difficult task at best. Identifying wild flowers is simple, but all flowers growing in the wild are not native. People have been bring flowering plants from all over the world to the Caribbean and many of those plants have hybridized to give new varieties. Does that make it a "native" to the Caribbean? The grapefruit is a prime example, it is listed as originating in both Barbados and Jamaica, but is native to neither because grapefruits are not natural!
Howard tried describing Caribbean plants in his multi-volume series, Flora of the Lesser Antilles (1974-1989, . He lists over 3000 species with 2100 being thought to be native. There are several disagreement involving his work. One, he listed anything native to the New World as being native to the Caribbean and two, he didn't do much of the collecting himself, only identifying specimens sent to him. This means that he included plants from Mexico and Central American that may not truly be native and may have missed other plants simply because no one sent them!
The Islands Resources Foundation is trying to expand and verify the data by Howard and have already found close to 3000 plants on Antigua alone (Personal communication). They traveled with two botanist to neighboring Nevis, a more mountainous and less developed island, where Howard lists just over 500 species and in two days of collecting got 70 new species, they estimate that there may be over 5000, a ten-fold difference. Many of the species though were small and non-flowering.
Several flowering species native to the Caribbean include the Plumeria and the Night-Blooming Cereus, both are symbiotic with certain species of insect found only in the Eastern Caribbean. There are also 5 species of Ipomea that were used by the Carib Indians for spiritual medicine (P. Honeychurch, Caribbean Wild Plants and their Uses). Wedelia and lantana are both flowering and several species are native, but not all.
Succulents are definitely flowering plants and native to the Caribbean. Some Agaves (commonly known as Century Plants) have flower stalks 20 feet high. The first true Cacti discovered by Europeans are from the West Indies and they have lovely flowers that produce edible fruit.
The Trees also produce flowers and many are native, such as the Cannonball Tree (Couroupita guianensis) and the various types of Poui Trees (Tabebuia sp.). The Mahoe (Hibiscus elatus) is beautiful, but they have no idea where it originated! Please note that the brightly colored Poinciana Tree (Delonix regia) is from Madagascar!
If ones climbs up into the rain forest, there are numerous minute orchids, bromilliads, antheriums, and philodendrons, all of which flower and many of which are used as house plants!
Flowers native to the Caribbean, there are more being discovered every day!