With people traveling globally and imported plants coming in from around the world, we need to be careful. Locally grown and native Hawaiian plants are the best. We need to be mindful and cherish what we have — it could be easily lost.

A cautionary tale is the erythrina gall wasp. The insect invaded Manoa in April 2005 and quickly spread to all the Islands, wiping out erythrina trees. There are many kinds of erythrina in the world, and many have been brought to Hawai'i and planted all over in our parks, gardens and along our streets.

We have one native Hawaiian erythrina, what we call wiliwili. Scientists call this unique Hawaiian dryland treasure of a tree Erythrina sandwicensis.

Hawaiian plant lovers, botanical gardens that grow native Hawaiian plants and foresters were so concerned that we might lose all of the native Hawaiian wiliwili.

Some people took extraordinary measures with expensive insecticides, injected into the trunks or sprayed into the canopies, to try to protect the wiliwili. Some took the natural approach, by keeping trees healthy through composting, watering, keeping lawn grass, weed cutters and mowers away and clearing away alien weeds that would compete with the wiliwili for water and nutrients. They also cleared away grassy weeds like fountain and guinea grass, alien species that thrive with fire (wiliwili and other Hawaiian plants are usually killed by wildfires).

The wiliwili tree in my parents' yard in Makiki has died, and we are very sad. At my father-in-law's Foster Village house is a wiliwili, one that my husband planted. It looked nearly dead for a while, but we didn't give up on it. Now it has leaves with just a few galls and may flower this summer. We hope to keep it alive.

Hawaiian naturalist and akamai entomologist Steve Montgomery says his wiliwili in Foster Park is a friendship tree and a sign of hope and stress relief for his neighborhood.

It is not quite accurate to call the foreign imports "wiliwili." They are not native to Hawai'i so we could call them erythrina, or tiger's claw or coral trees.

For example, Erythrina variegata is from other parts of Polynesia, eastern Africa, India and Southeast Asia and regions in between. This was the tree that was planted all over the island, in traffic-calming medians like on Salt Lake Boulevard and Hunakai Street in Kahala.

These were planted in a mass (we call it a monoculture when you plant one kind of tree or plant). They used to put on a bright red flower show in January and February — until the invasive, proliferating gall wasp wiped them out. They died with bark hanging off them and had to be cut down for safety.

We have a nice coral tree from the Amazon with rough crinkly bark and orange flowers. This is called Erythrina crista-galli. They also were looking really bad with lots of dead wood and heavily galled leaves. Many of them have survived, with just a few galls.

Erythrina from Africa (where the wasp may have originated) may be the most resistant.

Vertical coral tree, also known as vertical "wiliwili" (Erythrina tropic coral) first came to Hawai'i in 1959. An odd tree seedling came to Foster Botanical Garden and grew into a magnificent Jack-and-the-beanstalk-size tree. Cuttings were shared all over, and people planted them as quick green landscape screens and windbreaks for farm crops. They did a nice job of blocking the views and winds on central Maui and as you drove the North Shore. The erythrina gall wasp wiped them out, and tall naked skeletons were left. Some, such as the trees by the Kahalu'u sewage treatment plant, looked alive, but the green was actually alien vines climbing up them.

Sadly, the big original mama tree at Foster Botanical Garden died, and now there's a gap of heat and sunlight in the garden. It was a special kama'aina alien tree that was one of a kind.

Exercising foresight, Alvin Yoshimura, of Lyon Arboretum, has been working with scientists statewide to stockpile and document Hawaiian wiliwili seeds to replant.

Heidi Bornhorst is a sustainable-landscape consultant. Submit questions at islandlife@honoluluadvertiser.com or Island Life, The Honolulu Advertiser, P.O. Box 3110, Honolulu, HI 96802. Letters may be published or distributed in print, electronic or other forms.