Fig. 1: Seedling of Passiflora foetida	Fig. 2: Stipitate glands on the stem

Recently, I discovered a mysterious seedling (Fig. 1) growing in one of my pots, which I now believe to be Passiflora foetida (Stinking Passionflower). Currently standing at approximately 15 centimetres in height, it does not appear to be a climber at all. Initially, I surmised it might be a Macaranga species from the Family Euphorbiaceae. A distinctive feature of the seedling is the spike-like stipitate glands (Fig. 2) visible on the stem around the base of the leaf stalks (petioles). Its identity was confirmed when the first tendril appeared. Ten years ago, I collected two ripe yellow fruits of this climber from the wild to examine their seeds. Afterward, I buried several seeds in a pot, but no seedlings emerged. This current seedling may be from that batch of seeds, as I have been reusing my potted soil over the years.

According to the 2022 Singapore flora checklist, there are no native Passiflora species in Singapore. The publication identified all four listed Passiflora species (Passiflora foetida, Passiflora laurifolia, Passiflora quadriglandulosa, and Passiflora suberosa)) as naturalised species. Notably, Passiflora quadriglandulosa was reported as a new record in Singapore in 2018, making it the rarest among them. My initial encounter with this species occurred in July 2010 at Bukit Timah Nature Reserve, which is also the site where specimens for the 2018 publication were collected. To provide an understanding of the prevalence of these four naturalised species, their observation counts, as reported on the iNaturalist website viewed on 22 June 2025, are presented in Table 1.

The Singapore flora checklist excludes cultivated plants, resulting in the omission of cultivated Passiflora species found in Singapore. The iNaturalist website lists 7 Passiflora species from Singapore. In addition to the 4 species listed in the Singapore flora checklist, the remaining 3 species indicated on the iNaturalist website are Passiflora pallida, Passiflora vesicaria, and Passiflora edulis (Table 2).

Besides Passiflora edulis (Common Passionfruit) which is cultivated locally for its fruits, I have not observed Passiflora pallida and Passiflora vesicaria, although they appear to be relatively common based on observations from the iNaturalist website. Passiflora pallida and Passiflora vesicaria closely resemble Passiflora suberosa and Passiflora foetida, respectively. Neither Passiflora pallida nor Passiflora vesicaria are listed on NParks’ Flora & Fauna Web. According to a 2014 publication [2], there is a plant grouping known as the Passiflora suberosa complex that consists of two species and two subspecies. This complexity may be discussed at another time. As for Passiflora vesicaria, it was once synonymized with Passiflora foetida, but was restored to full species status in 2013 according to the Wikipedia website. Since differentiating these closely resembling species is challenging, I will focus on the two species named in the Singapore flora checklist for my Passiflora image collections.

Regarding the Passiflora foetida in my pot, I will provide care until it matures. It is hoped that it will ultimately produce flowers and bear fruit.

Reference:

[1] Ho BC, Lua HK, Leong PKF, Lindsay S, Seah WW, Ibrahim B, Loo AHB, Koh SL, Ibrahim A, Athen P. New records and rediscoveries of vascular plants in Bukit Timah Nature Reserve, Singapore. Gardens' Bulletin Singapore 2018;70(1):33-55. | Read article |

[2] Porter-Utley K. A revision of Passiflora L. subgenus Decaloba (DC.) Rchb. supersection Cieca (Medik.) J. M. MacDougal & Feuillet (Passifloraceae). PhytoKeys 2014;43:1-224. | Read article |