I'm not very good with cuttings. But I would reccomend growing this tree from seed. The seeds of "kou" (Hawaiian for Cordia subcordata) are in the hard woody fruits. The are a few seed to each fruit (fruits resemble nuts and should be cracked or smashed open). I have two seedlings that are both roughly over a foot tall. I uprooted these seedlings when the only leaves they had were their seed leaves. They just popped out of the red dirt (since theres kou trees planted in the landscape here) Roots should be stronger and growth should be quick. From my experience this plant is not very picky about soil, and it will tolerate being in a container for relativelty long periods of time (my two plants have been in four inch green pots for more than half a year and they still show slow but healthy growth.

Hi,
The photo is no longer visible and this thread is ancient but, I'm very curious how your Geiger experiment turned out. I'm interested in this beautiful tree too even though I live all the way in the North.