Asi-patravana is a forest where there are [palm trees with] leaves like [sharpened] swords; it is the name of a particular hell.

NOTE. Śrīmad-Bhāgavatam 5.26.7 lists the important hells in Naraka thus:

tatra haike narakān eka-viṁśatiṁ gaṇayanti atha tāṁs te rājan nāma-rūpa-lakṣaṇato ’nukramiṣyāmas tāmisro ’ndhatāmisro rauravo mahārauravaḥ kumbhīpākaḥ kālasūtram asipatravanaṁ sūkaramukham andhakūpaḥ kṛmibhojanaḥ sandaṁśas taptasūrmir vajrakaṇṭaka-śālmalī vaitaraṇī pūyodaḥ prāṇarodho viśasanaṁ lālābhakṣaḥ sārameyādanam avīcir ayaḥpānam iti; kiñca kṣārakardamo rakṣogaṇa-bhojanaḥ śūlaproto dandaśūko ’vaṭa-nirodhanaḥ paryāvartanaḥ sūcīmukham ity aṣṭā-viṁśatir narakā vividha-yātanā-bhūmayaḥ.

Some authorities say that there is a total of twenty-one hellish planets, and some say twenty-eight. My dear King, I shall outline all of them according to their names, forms and symptoms. The names of the different hells are as follows: Tāmisra, Andhatāmisra, Raurava, Mahāraurava, Kumbhīpāka, Kālasūtra, Asi-patravana, Sūkaramukha, Andhakūpa, Kṛmibhojana, Sandaṁśa, Taptasūrmi, Vajrakaṇṭaka-śālmalī, Vaitaraṇī, Pūyoda, Prāṇarodha, Viśasana, Lālābhakṣa, Sārameyādana, Avīci, Ayaḥpāna, Kṣārakardama, Rakṣogaṇa-bhojana, Śūlaprota, Dandaśūka, Avaṭa-nirodhana, Paryāvartana and Sūcīmukha. All these planets are meant for punishing the living entities.

Vaitaraṇī is described in Śrīmad-Bhāgavatam 5.26.22 thus:

ye tv iha vai rājanyā rāja-puruṣā vā apākhaṇḍā dharma-setūn bhindanti te samparetya vaitaraṇyāṁ nipatanti bhinna-maryādās tasyāṁ niraya-parikhā-bhūtāyāṁ nadyāṁ yādo-gaṇair itas tato bhakṣyamāṇā ātmanā na viyujyamānāś cāsubhir uhyamānāḥ svāghena karma-pākam anusmaranto viṇ-mūtra-pūya-śoṇita-keśa-nakhāsthi-medo-māṁsa-vasā-vāhinyām upatapyante.

A person who is born into a responsible family—such as a kṣatriya, a member of royalty or a government servant—but who neglects to execute his prescribed duties according to religious principles, and who thus becomes degraded,  falls down at the time of death into the river of hell known as Vaitaraṇī. This river, which is a moat surrounding hell, is full of ferocious aquatic animals. When a sinful man is thrown into the river Vaitaraṇī, the aquatic animals there immediately begin to eat him, but because of his extremely sinful life, he does not leave his body. He constantly remembers his sinful activities and suffers terribly in that river, which is full of stool, urine, pus, blood, hair, nails, bones, marrow, flesh and fat.

Śrīmad-Bhāgavatam 5.26.15 describes Asi-patravana thus:

yas tv iha vai nija-veda-pathād anāpady apagataḥ pākhaṇḍaṁ copagatas tam asi-patravanaṁ praveśya kaśayā praharanti tatra hāsāv itas tato dhāvamāna ubhayato dhārais tāla-vanāsi-patraiś chidyamāna-sarvāṅgo hā hato ’smīti paramayā vedanayā mūrcchitaḥ pade pade nipatati sva-dharmahā pākhaṇḍānugataṁ phalaṁ bhuṅkte.

If a person deviates from the path of the Vedas in the absence of an emergency, the servants of Yamarāja put him into the hell called Asi-patravana, where they beat him with whips. When he runs hither and thither, fleeing from the extreme pain, on all sides he runs into palm trees with leaves like sharpened swords. Thus injured all over his body and fainting at every step, he cries out, “Oh, what shall I do now! How shall I be saved!” This is how one suffers who deviates from the accepted religious principles.