Many types of ohia


I am currently clearing a lot (500-foot elevation) in Orchidland to build my house. Being cognizant of the value and statue of the ohia trees, I’m being careful to save absolutely as many as possible. My concern, however, is in the sickly, thin nature of most ohias in this area with or without nearby strawberry guava groves, which I’m removing with glee! I believe I have seen ohias in the Hawaii Volcanoes National Park that are abundantly full and appear quite healthy. Am I comparing two different species, or does elevation/rain/temperature have that much affect upon these trees? Also are there any treatments/fertilizers that would improve their appearance and general health of these trees? Thank you. Sincerely, A.C.

You may be comparing two different species; there are four distinct species endemic to Hawaii, as well as eight different varieties of ohia.

In addition to genetics, there are environmental factors which will cause physical variations in the trees. Elevation, rain and temperature all have an effect upon these trees. With trees in general, the shapes of leaves from trees growing in hot, dry deserts are often small in order to conserve water loss through the leaf.

Contrast this to the large-leafed plants of the tropics. Ohias occur in a wide range of habitats, from just above sea level to 8,200 feet; from dry forests with less than 16 inches of annual rainfall to wet forests with more than 33 feet of annual rainfall.

This along with its genetic propensity for variation will produce trees of diverse appearance. The species name, polymorpha, actually means many forms. Thus tree height and form, leaf shape and flower color are highly variable.

Ohia trees can be damaged and killed from a lack of water. During periods of drought especially, supplemental watering will be needed. Trees growing in the pahoehoe lava may do well when young and water requirements are low.

Nevertheless, as trees increase in size, if adequate water is not supplied, they can dry out and even die. Mulch will help, but of course, not piled against the trunk.

Since ohias are adapted to grow in low nutrient soils, beware of over-fertilizing.

Slow-release fertilizers or natural compost is best.

With all this in mind, your sickly ohias may be just that and not a matter of genetic or environmental variation. An overabundance of rain coupled with poor drainage will certainly cause trouble with ohias. On the other hand, drought can also be detrimental to the health of the trees. Nothing can be done about the waterlogged soils, but supplemental watering and mulch will help under drought conditions.

Dear Garden Guy, I have a dead podocarpus tree in my yard. Instead of cutting it down, I would like to trim the branches and attach orchids or bromeliads to the trunk of the tree like the one at the Chinese Church, corner of Mohouli and Kinoole. I know the dead tree will eventually deteriorate. Approximately how long will that take? Trunk diameter is about 12 inches. Do I need to be concerned about insect infestation, termites, etc.? I live in rainy Kaumana. Thanks so much for your wonderful advice!

It’s very difficult to give you a time for the deterioration of the tree as there are a number of variable factors involved. Yet, with the size trunk you mentioned, my guess is that the tree will remain intact for many years, at least long enough that it would be worth the time invested to attach the various plants and enjoy the beauty while you can.

The other question might be, “Is the tree truly dead?” Sometimes a tree looks dead, but some part of it, even an underground part, may still be alive. If so, this would prolong the time before the tree eventually decays. And yes, insects such as ants and termites often colonize dead wood. But again, I would take that chance. Treatments can always be made later.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at askthegardenguy@earthlink.net.

 

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