Native (?) Wildflowers of Hawaii

The Kahili ginger (Hedychium gardnerianum) 
seems perfectly at home in Hawaii, but
so much so that it has become one of the 
most troublesome weeds there. It's prolifically 
spreading rhizomes choke out native vegetation
wherever it takes hold. It comes originally from
India.

We usually think of wildflowers as colorful displays bursting forth after the winter thaw in an alpine meadow, or after a rainstorm in the desert. In the tropics though, we're looking for flowers popping up randomly in the rainforest, or perhaps on dry lava slopes.

 A more relevant question about Hawaii is "what are the native plants here?" It's a  more complicated and perplexing question than you might think. The hibiscus, orchids, plumeria, gingers, and heliconias we associate with this island paradise were all brought in by European visitors and settlers - so not native. The many climbing aroids - philodendrons, pothos, and monsteras that climb the trees in the tropical rainforests, along with most of the palms one sees, also came from elsewhere. Some have become invasive weeds. 

Plants brought by Europeans caused the most radical and disruptive changes to the local flora, but the vegetation has been continuously changing ever since the first volcanic cone of this island chain emerged above water. 

Before the Europeans, Polynesian settlers originally from the the Indo-Malayan region, brought in coconuts, noni fruits, breadfruit, taro, sugar cane, bananas, and other useful plants, along with chickens and pigs. So that brought about a significant disturbance in the flora as well.

So what plants were in the islands before the first Polynesian settlers arrived? There was of course a rich flora there at that time, what we might consider the true indigenous flora of Hawaii, but little that would be familiar to anyone. Even that native flora, however, arrived piecemeal over time. 

Ferns were among the first plants to arrive in 
Hawaii, and are still among the first to colonize
new lava flows.

When that first volcanic cone appeared millions of years ago, there was of course no native flora at all. The first plant life to arrive was of spore-dispersed plants like ferns and mosses (along with lichens, which are combinations of fungi and algae). The most familiar descendent of these wind-dispersed plants would probably be the Hawaiian tree fern, Cibotium menziesii, which can be seen in many parts of the rainforest, and are prominent in the undisturbed forest around the Kilauea volcano, in Volcanos National Park on the island of Hawaii. 

Hawaiian tree ferns in Volcanos National Park.

There are some salt-tolerant plants flowering plants, like the beach morning glory and "half-flower" (Scaevola spp.) that are everywhere along tropical beaches, and their seeds probably floated to the islands. 

Scaevola is a widespread genus of salt-tolerant
plants common along tropical beaches in the
Pacific region. Several indigenous species have 
evolved in Hawaii.

The beach morning glory (Ipomoea pes-caprae) 
is common on tropical and
subtropical beaches around the world.

Metrosideros polymorpha is still the dominant
tree in most parts of Hawaii.

The first woody plant to arrive was a species of Metrosideros, a relative of Eucalyptus and guava. It had no competition at first, and became the dominant tree of the Hawaiian rainforest. It evolved into many forms, including dwarf shrubs at high elevations. By some accounts there are now five species of Metrosideros indigenous to Hawaii, with M. polymorpha the dominant species. Experts estimate that about 275 flowering plant species migrated to Hawaii in the pre-human era, and from that base evolved into about 1000 endemic species.

In the Alakai Swamp on Kauai, Metrosideros polymorpha
grows as a low-lying shrub.

A silversword plant in bloom inside the 
Haleakala Crater on Maui.

Another indigenous plant is the odd-looking silversword  (Argyroxiphium sandwicense), found in exposed areas of the Hawaiian volcanos, and most readily seen in Haleakala Crater on Maui. There are some nineteen species of the palm genus, Pritchardia, that are found only in Hawaii.

So there are interesting native plants to be found in Hawaii, if you know where to look.

Nineteen species of the genus Pritchardia are the
only palms endemic to Hawaii.

The pink knotweed, Persicaria capitata, forms conspicuous
pink patches along the saddle road that crosses the island
of Hawaii. It is, however, a native of Asia.

I thought I had found a native species of Passiflora with distinctive feather-like bracts that wrap around the fruit as it develops. It turned out, though, that it was another import from tropical America, Passiflora foetida. (The petals on the flower have already
curled up.)