The Pali term "rukkhamūla" means "the fact to remain beneath a tree".
"rukkha" = "tree"; "mūla" = "root"
The bhikkhu who takes the habit to remain beneath a tree is called a "rukkha mūlika". When this practice is conveniently put into practice, with steadiness and diligence, with the determination of not breaking it, we say that there is "rukkhamūlikaṅga" (a state of mind of the abode beneath a tree).
For adopting this dhutaṅga, it is convenient to pronounce the following phrase whether in Pali, whether in the language of one's choice...
«channaṃ paṭikkhipāmi, rukkhamūlikaṅgaṃ samādhiyāmi.»
«I renounce to the spots sheltered by a roof, I will train into dwelling beneath a tree.»
The bhikkhu who is a noble practitioner of the rukkhamūla dhutaṅga is not authorised to choose a tree that is convenient for himself, neither to prepare (cleaning, sweeping the leaves and the stones, etc.) the spot that he is about to occupy beneath a tree. On the other hand, he can set apart the leaves (from the spot where he is about to settle himself) by means of the foot.
The bhikkhu who is an intermediate practitioner of the rukkhamūla dhutaṅga get prepared for himself (cleaning, sweeping the leaves and the stones, etc.), by person of passage, the spot that he is about to occupy beneath a tree. He cannot however call a person specially allotted for this duty. The intermediate practitioner (and in stronger reason the ordinary one) can also erect a folding screen, walls and doors, but obviously no roof.
The bhikkhu who is an ordinary practitioner of the rukkhamūla dhutaṅga can get levelled the earth (from the spot where he is intending to settle himself) in order to make it regular, installed a mat, he can arrange his sitting spot (beneath the tree where he dwells) in the way he finds suitable for himself. Contrary to the intermediate practitioner, he can make a special request to a person (laity, novice, etc.) so as to ask him to perform one of these duties.
By practising the rukkhamūla dhutaṅga, we can benefit of one the following advantages...
Remark: the practice of a dhutaṅga alone enables one to understand its advantages.
If a bhikkhu who practises the rukkhamūla dhutaṅga, with the intention to be sheltered by a roof, enter under a roof, even for listening to the dhamma, as soon as he becomes aware that dawn is drawing near, if he ever remains a single moment more under this roof, he breaks his dhutaṅga. Under such circumstances, he must go out and install himself whether beneath a tree, whether on the bare earth (on an unsheltered spot), and he will thus avoid to break his dhutaṅga.
Buddha told that living at the foot of a tree requires no expenses, we are blameless, we agree with the fourth among the four autonomies (managing to contented by what we have, without having to depend on a donor). There is no better spot for that. We enjoy a calm atmosphere, the mind is serene, in peace with itself.
Buddha, during his last existence, took birth beneath a tree, reached omniscience beneath a tree, gave his first teaching beneath a tree, and finally, he got extinct into parinibbāna beneath a tree. The spot situated at the foot of a tree is the chosen one of Buddha and ariyās.
For all the above mentioned reasons, given that it (the foot of a tree) is a noble spot by itself, bhikkhus who grew mature in wisdom, it is convenient for them to adopt this dhutaṅga.
According to the "visuddhi magga", there are trees at whose feet it is convenient to dwell, and others beneath which it is not convenient to dwell. Here are the trees beneath which it is not proper that a bhikkhu, practising the rukkhamūla dhutaṅga, dwells:
It is not proper that a bhikkhu who practises the rukkhamūla dhutaṅga, dwells at the foot of one of these 7 kinds of trees, as they are likely to put him into danger, cause him hassles, undermine his concentration, but not incite him to break his dhutaṅga.
The bhikkhu who practises the rukkhamūla dhutaṅga is liable to dwell at the foot of the tree that doesn't belong to the category of the 7 kinds of above mentioned trees, and on a spot where no danger, agitation or noise do prevail, so that his samādhi may be properly developed.
In the "buddhavaṃsa" commentaries, are expounded the 10 virtues cultivated through the practice of dwelling at the foot of a tree:
In the commentaries "buddhavaṃsa", are expounded the 8 inconveniences of a sheltered lodging, or having at least one roof (wooden, made of leaves, etc.):
In order to divide the saṃgha, the monk Devadata had formulated five requirements before Buddha, one of them being: «(...) May all the monks sleep beneath a tree. Do decree it to be a great offence should any monk spend overnight under a roof.» Buddha had replied to him: «(...) May the monks wishing to sleep beneath a tree sleep there! May the monks wishing to sleep under a roof sleep there!» When he gave his answer in detail, he specified: «I have authorised bhikkhus who practise the rukkhamūlika dhutaṅga to dwell in a monastery up to eight months a year.»
In the commentaries (aṭṭhakathās), it is written: «The one who chooses to dwell beneath a tree can however reside within a monastery (all over the year), except four months at once.»
In the vinaya, it is also told: «During the monsoon (the four months of the rainy season), he cannot live outside of a monastery, beneath a tree.» and «During the eight other months (cold and hot season), it is permitted to remain beneath a tree.»
Regarding the abbhokāsika dhutaṅga, it is outlined in the vinaya: «Should a bhikkhu spend the vassa on the bare earth, he commits a dukkaṭa.» It is therefore impossible to practise the abbhokāsika dhutaṅga during the vassa. During the monsoon, a bhikkhu who practises the rukkhamūlika or abbhokāsika dhutaṅga is therefore supposed to dwell in a sheltered lodging.
Besides, the «visuddhi magga» is telling us: «The (rukkhamūlika or abbhokāsika dhutaṅga) cannot be broken by the fact to remain under a roof. It is convenient (for the practitioner of these dhutaṅgas) to proceed under a roof in order to listen to the dhamma or to satisfy various needs. However, by remaining under a roof at the time of dawn, the dhutaṅga(s) is (are) broken.»
According to these assertions, the practice of the abbhokāsika dhutaṅga doesn't mean that we constantly remain on the bare earth; we can proceed under a roof in order to study the dhamma teachings, perform various monastic procedures such as the uposatha, the pavāraṇā..., listen to some teachings, etc., without necessarily breaking this dhutaṅga. The same thing exactly applies for the rukkhamūlika dhutaṅga.
Origin: Book in Burmese language
Author: Monk Devinda
Translator: Monk Dhamma Sāmi
Date of translation: 2004, January
Update: 2005, June the 18th