Is passionfruit subject to the laws of orlah?

Answer

Trees are subject to orah laws, not vegetables. What, then, is the definition of a “tree”?

According to halacha, perennial plants that grow from a trunk are considered trees. This is why bananas are considered vegetables: while they are perennial, they grow from the root. There are, however, several species that are considered borderline in terms of fruit/vegetable status (such as eggplant, papaya, babaco, pineapple, pitaya, and passionfruit), so some poskim laid down additional criteria for plants to be considered vegetables:

(1) Plants with a hollow trunk; (2) Plants that die before they reach three years (the Chazon Ish explains that it doesn’t make sense that the Torah would prohibit a tree altogether so we could never benefit from its fruit); (3) Plants whose quantity and quality of fruit diminish from year to year.

In practice, if conditions (2) and (3) are met, the plant is considered a vegetable, like is the case with eggplant.

Some authorities add another condition: (4) If the plant bears fruit within the year, it is also considered a vegetable; most Sephardi poskim rule accordingly.

The passionfruit plant bears fruit within its first year and its fruit diminishes in quantity and quality from year to year—but this is due to poor growing conditions, and is not an inherent characteristic of the plant. The trunk also has a very small hole in the center, the size of a needle.

In practice, the poskim dispute whether passionfruit is subject to the laws of orlah. Most Ashkenazi poskim are stringent, while the Sephardi poskim are traditionally lenient.

Since you plant passionfruit as a living fence, even if you are Ashkenazi, it is possible to be lenient and eat its fruit without counting orlah years. This is true even if the original intent was also to eat the fruit (see Hilchot Ha’aretz, p. 134).

See here for the relevant chapter from the book Hilchot Ha'aretz.