Orla applies to a tree growing inside a house. Since orla depends on the tree being planted in the ground, having a roof above it does not prevent orla from applying. Likewise, orla applies to a tree planted on a rooftop. Even though the roof separates the tree from the earth, the roof itself is connected to the ground through the walls. It is therefore considered part of the ground, and the tree growing on it is considered planted in the earth (SA YD 294:26).
One who plants a sapling in a perforated pot is considered to have planted it in the ground, and the orla years are counted from then. If one plants a tree in an earthenware pot, even one without holes, the tree is also considered planted in the earth, and orla applies to it, because its roots can break through the earthenware. Even before they do so, they are considered to draw nourishment from the ground. Some maintain that orla applies even to a tree growing in a metal pot, despite the fact that its roots clearly cannot penetrate the metal.[9]
With modern advances in fertilization and irrigation, many trees are now capable of bearing abundant fruit already in their third year. Since one may not derive benefit from that fruit, and it is costly to leave valuable agricultural land unproductive, farmers developed a practical solution. They keep the trees for about two years in nurseries, in perforated plastic pots, where they occupy little space and cost less to maintain. In the third year, they transfer them to the ground, where they can take root more firmly and then produce abundant fruit in the fourth year, when the fruit is no longer orla.
In practice, because we are concerned for the view that the orla count may not begin in an unperforated plastic pot, two conditions must be met if time spent in nursery pots is to count toward the three orla years according to all opinions. First, the pot must have a hole large enough for a small root, so that it is considered connected to the ground. Accepted practice requires a hole at least 2.5 cm in diameter.[10] Second, when the sapling is transferred from the pot into the ground, one must take care that the soil clump around the roots does not fall apart. After the fact, even if most of it crumbled, as long as the roots still remain embedded in enough soil to sustain the tree, one need not restart the count. If, however, almost all the clump broke apart, so that even with watering and care the tree would likely not survive for 14 days unless it were replanted, then one must begin counting the three orla years anew.[11]
[9]. According to Rosh (Teshuvot Ha-Rosh 2:4) and Tur, as explained in Ḥavot Binyamin 2:4 and Minḥat Shlomo 1:70, orla applies only to a tree growing in an unperforated earthenware pot. If the tree grows in any other unperforated container, even one made of wood, the orla count does not begin. If the tree is later transplanted into the ground, one must begin the three-year count anew. Rambam, however, writes: “If one plants in an unperforated pot, orla applies. Although such a pot is not considered like the ground for seeds, it is considered like the ground for trees” (MT, Laws of Second Tithe and Fourth-Year Fruit 10:8). SA YD 294:26 rules likewise, and most authorities accept this view. Nevertheless, they disagree about which containers Rambam had in mind. Some say he referred only to wooden pots and the like, which roots can sometimes break through; containers that roots cannot penetrate do not start the orla count (R. Herzog, Pesakim u-Ketavim 3:10). Others say that orla applies to trees in every kind of pot, even metal, because tree roots are considered so powerful that no barrier fully cuts off their nourishment from the earth (Minḥat Shlomo 3:158:20). Some remain uncertain (Har Tzvi, Zera’im 2:15:3; Lehorot Natan 6:101). Since this is a doubt involving a Torah prohibition, one should be stringent with trees growing in unperforated metal or wooden pots. The stringency cuts both ways: while the sapling remains in such a pot, one observes orla; if it is later transplanted into the ground, one begins counting the three years again.
[10]. Saplings are generally grown in plastic bags with holes. If the bag is thick and has no hole at all, the roots of a small tree cannot penetrate it. According to Rosh, the orla count does not begin for a tree grown in such a bag. Some understand Rambam and those who follow him the same way, as explained above. Therefore, one should make a hole in the bag, so that the sapling is considered connected to the ground and the orla count can begin. We learn from other laws that the required opening is the size of a small root (Uktzin 2:10). Shabbat 95b teaches that this is larger than the opening that lets liquid enter, which is less than two millimeters, and smaller than an olive, which by our standard measure is about 1.5 cm. In practice, the accepted custom is to be stringent and equate a “small root” with a large kezayit, yielding a required opening of 2.5 cm (R. Goren, Teḥumin 1, p. 158; Mishpetei Eretz 3:7, note 1). After the fact, however, even a one-centimeter opening may suffice, since it is already larger than the size of a small root. In addition, Rambam maintains that orla applies even in an unperforated pot. Although some understand him to refer only to a wooden pot, which roots can break through, a plastic nursery bag may also be penetrated by roots, in which case most authorities would say no hole is needed at all. So writes R. Goren there. Moreover, even when there is only a tiny hole of one millimeter, because the bag is soft, any root that passes through can widen it beyond the size of an olive. The bag may therefore have the status of a perforated clay pot, which even according to Rosh counts as perforated. Furthermore, some maintain that even when a tree grows in a fully unperforated pot and the orla count does not begin there, the time spent in the pot still counts toward its three years, just as we count the years of a sapling brought from abroad (Beit David 2:1; Even ha-Ezel, cited in Kerem Tziyon). See also the extensive article by my colleague R. Azriel Ariel in Ha-Torah Ve-ha-Aretz 1.
[11]. When saplings are transported from the nursery to the field, they sit on a truck with a metal floor. Some were concerned that during that time they are considered disconnected from the ground, and that upon being replanted, the orla count must begin again. They therefore required that, ideally, they be transported in a truck whose bed is perforated (R. Ovadia Yosef; Shevet HaLevi 5:156:3–4). Strictly speaking, however, this is unnecessary. The sapling remains with its soil clump intact, which continues to sustain it as before. A brief interruption of a few hours does not make it a new planting (R. Yisraeli, Ḥavot Binyamin 1:1; Minḥat Shlomo 3:158:19; 1:70; Mishpetei Eretz 3:9, note 7). This is especially so according to those who, following Rambam and most authorities, maintain that orla applies even to a sapling in a metal pot, and according to the view of Beit David mentioned at the end of the previous note. See also R. Azriel Ariel’s article cited above.
