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The Honolulu Advertiser
Posted on: Friday, February 2, 2007

Spring '06 rain may be killing our plants now

By Heidi Bornhorst

The intersection of East Manoa Road and O'ahu Avenue flooded during last year’s 43-day downpour. Many trees’ root systems were seriously weakened by the drenching but only now are starting to fail.

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Q. An elephant's ear tree in Manoa, a sausage tree at the Hale Koa Hotel — they just "fell apart." What is happening?

A. We think that last year's 43 days of rain has had big implications for trees and plants, and will continue so down the road.

Most plants do not like wet feet. Rice, kalo and mangrove are three of the few that do like soggy soil and can live and thrive with no oxygen for their roots.

Last March and April, we had rain like never before in Hawai'i. It just did not stop; a true monsoon type of rain pattern. I love rain, but 43 days was a pain.

Some plants died during the flood. Some died later. Some seemed to thrive and like it, but damage may have occurred.

One of my favorite plants is the native fragrant Kaua'i white hibiscus, Hibiscus waimeae or koki'o ke'o ke'o. Akamai landscapers know this as a drought tolerant, less-thirsty plant even though it lives in wet rainforesty Koke'e. After last year's deluge, they were slow to flower.

Usually in peak bloom by May and June, they kept sending out green growth after the flood. Then finally came an explosion of blooms — along with a pest we've been seeing on hibiscus in recent years, a new mealy bug. I was treating the bug-infected plants with peppermint soap when I noticed that the profuse blooms were going to seed and then the branch would die back. On a couple of plants, they died back all the way to the roots. We think that they suffered from lack of oxygen during the flood and then got a root rot. The profuse blooming was a stress response before the whole plant dying. Auwe!

A giant elephant's ear tree in Manoa fell apart the other night. And at the Hale Koa, we had a sausage tree that also disintegrated. These are monsoon-adapted trees with a survival strategy where they drop branches and get rid of all the vines and creepers that would overwhelm them in their native forests.

Things are blooming weirdly. Some plumerias never really lost their leaves in November, and many kept blooming all winter. Others lost their leaves only last month.

Fragrant gingers have bloomed throughout winter. I put lights on mine at dusk to extend the summer blooming season and I thought I was such a good horticulturist to have my apricot-colored ginger from Mr. Pang in Wahiawa bloom through December. Then, observant gardener Annie Moriyasu called to tell me those along the Pali highway are still in full bloom (this is 'awapuhi melemele, yellow ginger or Hedychium flavescens — a native of northeastern India and the Himalayas that can live at elevations up to 6,500 feet).

Since we had a monsoon and these are from a monsoon climate, no wonder they are so happy and floriferous even in our Hawaiian winter.

I scored some Pirie mangoes last month, and I'm seeing trees full of blooms and fruit. I was admiring a tree in Manoa that was one-third in bloom and BAM! — down came a mango, whacking a nearby car. We all hungrily looked for it. The birds had eaten most of it, but we were willing to share. My friend said she had one just like it for dinner the night before, and it was 'ono.

I would love to hear from readers about funny-kine blooming, fruiting or plant growth in their gardens, in our urban forests and parks or in the wild, from those 43 days of monsoon rains almost a year ago.

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