By Jan TenBruggencate
Advertiser Columnist

Native Hawaiian plants are often characterized as being incapable of competing against the threat of alien weeds, alien insects and other challenges.

Hawaiian plants are notorious for their lack of self-protective mechanisms. Hawaiian relatives of thorny plants often have lost their thorns, and local relatives of bad-tasting plants have lost their bite.

Scientists say this is probably because an environment with no grazing animals provided no incentive for putting energy into growing thorns or developing toxic or bad-tasting chemicals.

But there's one thing Hawaiian plants have done well: evolve so they can take advantage of harsh environmental conditions that other plants find too challenging.

A few years ago, botanists on the Big Island said they feared for native plants in a region being invaded by the weedy fayatree or firetree, Myrica faya.

Those native plants had found a home, and a way to survive, in a terrain with exceedingly few soil nutrients. Weeds couldn't compete against them there.

The firetree that has encroached into that habitat is capable of fertilizing itself, fixing nitrogen in its root nodules. Nitrogen improves the soil fertility, so other weeds can get a roothold.

Suddenly the native plants' adaptation to poor soils no longer worked for them.

A small group of friends recently swam to a remote, rocky beach along Moloka'i's north shore and found another cluster of natives adapted to inhospitable terrain.

We came across a vertical cliff just a few feet from the sea. Salt spray swept the rock all year long; in winter, breakers crashed directly against the cliff bottom, rolling boulders against the black rock.

The base of the cliff was devoid of vegetation, but about 6 feet up was where we spotted a community of hardy natives, tenuously grasping the cracks and holes in the cliff.

There were clusters of a leafy yellow-green plant, described by our group's plant expert as a daisy relative called Tetramolopium sylvae — the only member of its clan to live on sea cliffs.

A pretty, small rosette of thick leaves was a gardenia and coffee relative, whose closer kin, known as manono, live in the high, wet forests.

There was a plant with leaves shaped like curved swords, called Schiedea globosa, and a primrose relative called Lysimachia mauritiana.

Up higher on the cliff, beyond the surf zone, there were other native plants mixed with aliens. But down in what must be one of the saltiest, most inhospitable spots in all of Hawai'i, was a native garden, holding its own against the tide.

Jan TenBruggencate is The Advertiser's Kaua'i bureau chief and its science and environment writer. Contact him at (808) 245-3074 or e-mail jant@honoluluadvertiser.com.