Monday, November 11, 2013

Ficus pumila - Wonder Creeper or Creeping Horror

Since everyone is crazy about planting edible figs in Malaysia at this moment and as a continuation of my Long Figgy Tale, I would like to highlight the large diversity of figs, especially native ones that are around us or are easy to cultivate. Since figs are divided into six subgenera, I would cover at least one from each of the following 4 subgenera:

  1. Synoecia
  2. Sycamorus
  3. Urostigma
  4. Ficus

To start of the list, I will begin with the subgenus Synoecia, with a common fig that is probably very much overlooked and is also edible and has medicinal value: Ficus pumila

Ficus pumila
Synonyms: F. repens, F. hanceana, F. scandens, F. stipulata, F. longipedicellata
English name: Creeping fig, Climbing fig
Malay name: Ara jalar
Chinese name: 薜荔 (bi li), 石壁莲 (shi bi lian)

Subgenus: Synoecia
Section: Rhizocladus
Subsection: Plagiostigma

Ficus pumila is a fig plant under the subgenus Synoecia. Members of this subgenus are usually root climbers and have two distinct leaf types. Typical of this subgenus, Ficus pumila is dioecious and have functional female (only long style ovary for seed production) and hermaphrodite male with short-style ovary for wasp production. The synconia are light green with white spots and ripen to a dark purplish colour (those that drop green are most likely unfertilised synconia).
The mature stems of Ficus pumila. You can see the juvenile leaves that covers a brick wall on the lower portion of the picture.

The general appearance of this fig is a woody climber, with vines closely appressed to the substrate. They produce two different kind of leaves, a small and thinner one when they are juvenile and larger, more leathery leaves on the mature branches. Unlike the juvenile climbing stems, the mature branches do not climb but instead hang out from the supporting substrate. The Latin name pumila, meaning small, refers to the small juvenile leaves.
Here's another picture of Ficus pumila var. pumila climbing up a wall. This wall gets very hot in the afternoon, but it doesn't deter this tenacious fig from climbing up. The figs have just put out mature stems that have bigger leaves and juts out from the wall. They are so vigorous and tenacious that I am tempted to say that if your grandmother sat by the wall on the garden long enough, she would probably be smothered to death by Ficus pumila!
The synconia of Ficus pumila var. pumila. Note the white spots on the ostiole end of the synconia. This is taken at 1-Utama's Secret Garden.

On the climbing stems, roots that can arise from every node and they secrete a gum-like substance when they come in contact with suitable substrate to ensure that the plant gets a good firm grip on the supporting substrate. Hence it will destroy paintwork and wood surfaces wherever they are allowed to climb on. The overall appearance of the plant covering a wall is that of an ivy-covered wall. If the climbing/creeping branches reaches a tree, it will quickly smother the stem and then put out mature branches that bears fruit.

A climbing, juvenile shoot of Ficus pumila. After taking this shot, I gently teased the shoot off the wall...
The shoot from above after being pulled off the wall. Blue arrows shows the clasping roots at the internodes that had pieces of paint stuck to it. The yellow arrows indicate a node with clasping root primordia that had not begun secreting the gummy substance that adheres to the paint on the wall. These clasping roots that enable this fig to climb and stick to seemingly impossible surfaces are the reason why they are grouped into Section Rhizocladus.

Besides the horticultural variants like the variegated, oak-leafed (var. quercifolia) and curly-leafed that are just leaf variations of the common var. pumila, there is also another, more economically important variety, the var. awkeotsang.

The typical F. pumila var. pumila is distributed in Southern China and down to Malaysia and widely used worldwide for landscaping whilst the F. pumila var. awkeotsang is found in Taiwan, Fujian and South-eastern Zhejiang regions. In Taiwan, they are found at higher elevations whilst the var. pumila commonly grows on the lowlands. Recent studies also points to genetic difference in the wasps that pollinate F. pumila var. pumila and var. awkeotsang, hinting to a coevolutionary differentiation with this variety.

The leaves, and also the fruit of F. pumila is considered medicinal and edible, but not in the sense as a table fruit. The fruits are used to make a type of jelly that is very popular in the East. Whilst both variety (var. pumila and var. awkeotsang) can be used to make the jelly, it is the var. awkeotsang that gave rise to the name and fame of this jelly. The varietal name awkeotsang is the Hokkien romanization of Ai Yu Bing ( 爱玉冰 - ai guek seng, literally love jade ice) in which Ai Yu is supposedly the name of the daughter of the man who first started this dish in Taiwan.

The 'seeds' (actually drupes) of var. awkeotsang looks like little dots of dust, and is sometimes called wen zi tou (文字头 - top of the chinese character wen, NOT 蚊子头 - mosquito head, lol). Hence another name for this jelly is wen tou xue (文头雪 - wen character top snow) since it is quite commonly eaten with shaved ice.

So how does this jelly come about? A little biochemistry is involved in this jelly making process, which is sometimes called washing Ai Yu seed (in water). Pectin from the drupes (so called seeds) of F. pumila var. awkeotsang has quite high methyl side chains and will dissolve in water. High methyl pectin will only gel if the pH is low as low pH prevents the repulsion of the pectin chains. Thus this pectin remains in the sol (liquid) state when leached from the fruits/seeds. The seeds also have an enzyme, pectin methylesterase, which can break the ester bond between the methyl group and the pectin's carboxylate group: 

Pectin-COO-CH3 + PME = CH3OH + Pectin-COOH
(yes, methanol is released in the process. The amount is minuscule and would also have evaporated by the time the jelly is ready)
PME - pectin methylesterase
CH3OH - methanol

The demethylated pectin, in the presence of a divalent ion e.g. Ca2+ begins to interact with another chain, causing it to gel. That gives you the jelly that is Ai Yu jelly, wobbly and all. Some add slices of banana and lime juice, which not only provides flavour, but also increases the pectin content and lowers the pH, ensuring a nicely set gel. 
Side view of an immature synconia of Ficus pumila. It looks like a flattened pear-shaped fruit. The fruit will ripen to a purplish green colour that makes the fruit look like it was badly bruised.

To use F. pumila var. pumila, the ripe fruits need to be squeezed for the juices in it and then boiled to trigger the gelation process whereas in var. awkeotsang you only need to 'wash' the stuff from the 'seeds' in tepid water. Hence Ai Yu Jelly is usually made from var. awkeotsang  Because the presence of divalent cations are required for the gelling process, the mixture will not gel if you attempt to do this in ultrapure, mineral-free water.

In conclusion, whether one is growing Ficus pumila as as a decorative plant or for medicinal use, one should be aware that this fig can be a wonder creeper for covering up walls and ugly partitions or turn into a creeping horror for you that swallows up your wall or house in a swathe of green and refuses to die unless you pick off every little bits and pieces of its stem.
They will grow wherever there is light. moisture and nutrients. Here they are taking on a drain embankment by a golf course.
Ficus pumila can climb things that you think are impossible to climb. Here they have taken on and climbed up a metal post for the chain-link fence by a golf course. From the mature stems that flay out in all directions at the top of this metal post, the fig must be pretty pleased with its perch and the view from the top.

Note: For those that do not have a wall or a surface suitable for F. pumila var pumila or does not want to face off with the creeping horror, the variegated version (F. pumila Variegata) can be considered as a hanging pot plant since they are more 'well-behaved' and looks good in a pot. F. pumila Variegata are sold in many nurseries over here (and even in Tesco). Most people would not even think it is a fig tree as the leaves looks very much like a small variegated mint. On closer inspection, one can see and feel the root bumps at the nodes that will spring into action if allowed to come in contact with a suitable surface.

Note: Rønsted et al. (2006) indicate that placement of Ficus pumila in Rhizocladus is erroneous and inconsistent with molecular studies conducted.