Recently I learned that in Thailand, since the 1980s, and recently also in Cambodia by monks inspired by the Thai example, monks have been ordaining trees as a conservation/ecological activism.
What does the vinaya say which might be relevant? It seems to me that this might be a problem with rules on ordination, rites rituals, and encouragement of superstitions. But as it has been going on apparently for more than 35 years, and has been spreading, perhaps it is not problematic.
It is symbolic and not effective in terms of making trees part of the bhikkhu Sangha. Also it does not make the trees able to ordain others! 
I agree, it might be harder to obtain confirmation that trees are not dragons, which I understand is one of the checks you need to carry out before someone (or somethings? 
) can join the Sangha 
No responses to my original questions, but I think I understand why; it would be difficult to speak truthfully and directly to my question "What does the vinaya say which might be relevant? " without breaching customary etiquette and perhaps vinaya rules.
As far as I know, the Buddha did not establish (or even allow) the ordination of trees, symbolic ordination, use of what I assume is donated robes cloth like this, encouragement of superstitions. But I understand, if it is a breach of what is allowed, the discussion would probably be private among the ordained.
Which in Thailand will not include any women at this time, because I understand Thai Buddhist hierarchy teaches they are defective material.
I do not think this is harmless, funny, or consistent with the Dhamma. And I am willing to say this out of respect for the Dhamma, the Sangha, and (neither last nor least) the Buddha.
I suggest those involved consider, is the preservation of forests even environments condusive to meditation, consistent with homelessness, impermanence, Right effort?
There’s nothing secret about Theravada ordination.
You can read the monks proceedings here
The tree might fail the question about being human…
Regardless, the Buddha recommended we dwell at the foot of trees and practice in wilderness . I think it’s a nice symbolic effort. We need forest to provide quiet and solitude
Good that they are ordaining trees, next step could be to give ordination to women! …just saying 
"There’s nothing secret about Theravada ordination. "
I don’t see that anyone in the thread suggested there was; my reference to possible vinaya restrictions on responding to my question was based on awareness that there might be restrictions related to possible appearance of public criticism by monastics of monastics… It seems you inferred something different.
As a horticulturist, I am often saddened by the uncalled for destruction of trees in the city and suburban environments.
Many old and significant trees are removed without consultation or consideration for other environmental impacts just the Tree is in the way of a multinational developer or a road authority to make more money for themselves and their shareholders.
I really like this idea of “ ordaining “ trees as a part of conservation and ecology.
From living in the Australian bush many times I did witness several strange phenomenon of the forest trees communicating with each other alerting to oncoming danger with bushfires and information some how coming through the world when no tv s radios or telecommunications were available. This is known as the bush telegraph.
Trees are great…some of my best friends are trees…they like to talked to and hugged.
I like to include trees in the first precept to refrain from destroying living creatures.
This is my first post…hopefully not too controversial. 
The other day we were driving along the King’s Highway from Canberra towards the coast and passed a couple of eucalypts tied with saffron cloth. It didn’t occur to me that they might have been ordained.
