Last Saturday at the Botany Centre’s Function Hall, I gave a talk on the family of true gingers – Zingiberaceae – as part of the Community in Bloom gardening talk series. It was a sequel to an earlier one that covered on the Zingiberales order, which was delivered on 14 Mar 09. The latter was a bold attempt to introduce to the public a huge order of plants consisting of 8 families of flowering plants which are monocotyledons.
The Zingiberaceae is a family that consists of numerous herbaceous plants that have important economical, ornamental, medicinal and culinary uses. Many Singaporeans grow members of the true ginger family in their gardens, be it private or a community garden.
True gingers which are distinct from spiral gingers which are classified in a family of their own, Costaceae. Spiral gingers are popular ornamental tropical plants that are used quite prevalently in landscapes here in Singapore. There are two rather obvious differences between the plants from these two families.
True gingers emit an aromatic smell when a part of a plant is bruised whereas spiral gingers do not emit any smell. Spiral gingers, as their common name suggests, adopt an interesting growth habit where their leaves on a stem are arranged in a spiral manner. The leaves on a true ginger are produced distichously with respect to the leafy shoot (pseudostem).
I started my talk with gingers that most people are familiar with. Starting from the culinary gingers that are used in everyday cooking such as, Zingiber officinale (common ginger) and Alpinia galanga (greater galangal), my audience were brought on a discovery journey that gradually transit into the realm of ornamental gingers. In the talk, I took the opportunity to highlight some of the prettier and interesting ones such as Hedychium coronarium, also known as butterfly ginger that produces fragrant butterfly-shaped white flowers. The stunning Etlingera elatior or Torch Ginger, a towering and majestic plant with immense ornamental value, which also produces edible flower buds, was not forgotten.
After an introduction to a selection of various true ginger species that are worth growing, I shared with those present on how to grow them and solutions to problems that are commonly encountered during cultivation. A rather lively and interactive question-and-answer session then took place which lasted for about 45 mins. It was hoped that everyone benefited from the talk and sharing session.
The first instalment of the Root Awakening column for the month of July 09 was published yesterday. As usual, answers were provided for three gardening questions sent in by the readers of Straits Times Life!
One of the first questions revolves around the growing of fruit trees. This time, its about the rambutan. A reader asked why his/her rambutan tree fruits tend to fall off prematurely. Rambutans need a prolonged dry season to trigger flowering but they need to be well-irrigated to reduce the likelihood of water stress that will lead to premature abortion of young fruits.When a tree has started to produce fruit, remember to provide water to the tree. A ring of well-rotted compost can be added and bone meal supplementation can help to boost fruiting.
The second question asked why the leaves of the pomegranate dried up. The symptom described can be due to a number of causes. The plant may be grown in an overly windy condition. Young leaves can dry up as a result of strong, perpetual winds. Leaves could also dry up due to mite infestation. Mites can cause leaves to roll up and become distorted which eventually dry up. Cut away affected parts and spray with white summer oil to control mite population. It could also be due to insufficient light as pomegranate is a shrub that requires at least 6 hours of direct sunshine to grow. Overwatering may be a reason as well. Soil for growing pomegranate needs to be kept moist and not wet. Let soil dry out a little before watering again.
The last question enquired whether can subtropical fruits like avocados and lemons be grown in tropical Singapore. These trees can be grown in Singapore as they thrive and attain best quality in summers where there are longer daylight. It is best to buy ready plants that are known to produce in lowland tropical climates from local or overseas nurseries. Lemon can be grown in pots but fruits may not turn yellow when grown here.
In the July 09 issue of the Home Concepts magazine, I penned an article entitled ‘Spice of Life’ for the regular Garden Treats column. In it, I introduced five common trees that are sources of culinary spices. Spices is a term that is used to refer to dried plant parts that are used in small quantities to flavour the food we enjoy. Some of them also possess medicinal uses. On the other hand, the word ‘herbs’ is used to call entire plants or parts of a plant used in the fresh form for flavouring food. Both terms are used interchangably and have caused much confusion.
Depending on what are the spices, they can be derived from bark, leaves, flower buds, fruits, aril and rhizomes of plants. In my article, I introduced five common culinary spices and the reader can expect to see excellent pictures depicting the five spices, together with their leaves and fruits (where applicable)!
One of the first spices that was mentioned is the candlenut (Aleurites moluccanus, Euphorbiaceae). The part of plant used for flavouring purposes is the seed kernel of the candlenut fruit.
Another common spice, cinnamon, which is available in quills are derived from the bark of trees belonging to the genus Cinnamomum. Cinnamomum verum yields the true cinnamon whereas C. aromaticum is the source of Chinese cassia, which is often used to make the five spice powder. Both trees are members of the Lauraceae.
Clove is derived from the unopened flower buds of the tree, Szygnium aromaticum, a member of the Myrtaceae family. Common tropical fruits such as the jambu and guava are classified in the same family.
Mace & nutmeg come from the same tree, Myristica fragrans (Myristicaceae) and tamarind is derived from the fruits of Tamarindus indica, which is a member of the bean family, Fabaceae.
These five spices are derived from various tropical tree species which are well at home in the tropics. In Singapore, some of them are grown in our public parks or planted along our roads. To see some them all at once, pay a visit to the herb and spice gardens at Fort Canning Park and Singapore Botanic Gardens. Both green spaces have numerous mature trees and if one is there at the right time, he/she can see the trees in flower or producing fruit.
Last Saturday, I was involved in giving a guided tour at the Lifestyle Corner at HortPark. The tour and showcase were aimed at educating the public what geophytes are and various common vegetables and medicinal plants that belong to this category of plants. The showcase is now on until 27 Aug 09. It will run through GardenTech 2009 (14 to 18 Aug 09 @ HortPark) and visitors to this garden fair will also get a glimpse into how one can use geophytic plant parts for home decoration!
In brief, a geophyte is a herbaceous plant with an underground storage organ. Storage organs are reservoirs of carbohydrates, nutrients and water and play an important role in the plant’s survival during adverse climatic conditions and we, humans farm them for food and medicine.
Do you know how to differentiate a taproot, tuber, rhizome, bulb or corm? These are terms that are used to describe underground vegetables such as carrots, potatoes, gingers, cocoyams and onions, respectively.
A root tuber is a modified lateral root that stores food for the plant. Either the tip, part of or the whole lateral root swells up to become a storage organ. Root tubers have the internal and external cell and tissue structures of a typical root. Unlike stem tubers, root tubers do not have nodes. Common root tubers are cassava (Manihot esculenta) and sweet potato (Ipomoea batatas).
A stem tuber is a swollen, modified underground stem that stores food for the plant. Internally, a stem tuber has the typical cell structures of a stem, including a pith, vascular zones and a cortex. Common stem tubers include the potato (Solanum tuberosum) and Chinese yam (Dioscorea opposita).
A bulb is a vertical, underground stem consisting of a compressed stem (basal plate) and modified scale-like leaves. These modified leaves serve as the primary storage tissue. Bulbs are divided into tunicate and imbricate bulbs. A tunicate bulb such as onion (Allium cepa) and garlic (A. sativum) have a paper-like covering, or tunic, that protects the scales from drying and mechanical injury. A common imbricate bulb is the edible lily bulb (Lilium sp.) which is often an additive in Chinese herbal desserts.
A corm is a vertical, underground stem that serves as a storage organ with one or more internodes. It is encased in dry, papery, dead petiole sheaths which act as a covering that protects the corm from insect attack and water loss. Corms have internal solid tissues. This distinguishes them from bulbs, which are made up mostly of layered fleshy modified leaf scales. Common corms include the cocoyam (Colocasia esculenta) and water chestnut (Eleocharis dulcis).
A taproot is a swollen, tapering root that grows vertically downwards. Lateral, fibrous roots grow out from this main taproot. Many taproots are also modified to become storage organs. Taproots can be divided into 3 main cateogries: conical root – carrot (Daucus carota), fusiform root – radish (Raphanus sativa) and napiform root – yam bean (Pacchyrhizus erosus).
A rhizome is a swollen horizontal stem of a plant. It is usually found underground, often sending out roots and leafy shoots from its nodes. A rhizome is a modified stem, and the stem tissue itself serves as the primary storage tissue. A common rhizome is the cooking ginger (Zingiber officinale).
An interesting article written on the growing of fruit trees in highrise flats in Singapore was published on the Sunday Times just over the weekend. The article shared two success stories of Singaporeans who have succeeded in growing fruit trees in the highrise environment.
In Singapore, many highrise dwellers encounter the lack of sufficient sunshine that is required for growing these plants. Either they do not get the right intensity or they receive less than 4 hours or less of direct sunshine. To grow these edible plants properly, one has to locate them in a place at home where they can be exposed to a minimum of 6 hours of direct sunshine daily. Plants not receiving enough direct sunshine will exhibit slow growth, etiolation (elongation of shoots) and lack of flowers and fruits.
The first success story mentioned in the article focussed around Mr Lawrence Tan, who managed to grow and fruit grapes and Japanese muskmelons in tropical Singapore. Grapes have been reported before to be able to fruit here, but most of the time, the fruits are sparse and sour to taste. Muskmelons can also be grown easily without problems locally too.
The second person that was interviewed was Mr Ng Cheow Kheng, who is both my good friend, colleague and the Assistant Director of Streetscape Projects in National Parks Board (NParks). I have written a blog entry on this open patio before (viewable via this link). The two fruit trees that can be found Mr Ng’s growing area include the chiku tree and dwarf banana plant.
To be able to grow fruit trees in highrise apartments, one has to choose grafted varieties so that they can fruit while they still remain small and manageable. It is almost grow trees from seeds and expect them to fruit inside a pot. For these, they often need to attain their full height before fruit production commences. For banana plants, choose to grow dwarf varieties. By the way, bananas are totally herbaceous and are technically not classified as trees!
I was pleasantly surprised to see a feature story written on the growing of slipper orchids being published on Straits Times Life! today. The correspondent who did the interview was Andrew Tan and the grower that was featured in his article was Mr Joseph Yeo who happens to be a veteran member of the Green Culture Singapore discussion forum.
Like what was mentioned in the article, Joseph started his gardening interest in cacti and I remembered that he told me that he grew airplants (Tillandsia) and tropical pitcher plants (Nepenthes) before. He only started to grow slipper orchids (Paphiopedilums) only a few years ago. Similar to all plant groups he grew before, Joseph has always been fully committed to them and emerge soon after, as a subject expert.
Via his generous sharing of practical growing tips and posting of excellent photographs as a testimony of his great gardening skills on the Green Culture Singapore discussion forum, many fellow gardeners are inspired and given good guidance to grow this group of orchids which have been viewed as rather challenging to grow in tropical Singapore.
Garcinia xanthochymus is a close relative of the tree that bears the common edible mangosteen (Garcinia mangostana) which has been crowned the ‘Queen’ of tropical fruits. Also known as Garcinia tinctoria, Garcinia xanthochymus is commonly referred via an assortment of names such as the eggtree, gamboge tree, sour mangosteen, Himalayan garcinia and false mangosteen. It belongs to the Clusiaceae family (Guttiferae).
Garcinia xanthochymus originated probably from India and Burma. It occurs in the wild, growing in the hills of South India and can also be found widely distributed in the hill forests of the Eastern Himalayas and hence the common name ‘Himalayan garcinia ‘. In Singapore, this species of Garcinia appears to be rather rare and the place where I first encountered the plant was in HortPark.
The Garcinia species is rather bushy and adopts a rather attractive, pyramidal growth habit that can be likened to a Christmas tree. Its large leaves are linear in shape, dark green, thick and leathery in texture and they hand down from the stiff branches that extend outwards in all directions from the main trunk. It is a slow-growing tree like many other Garcinia species and can attain a height of 10 m.
Like other species in the same genus, male and female flowers usually occur on separate plants. Garcinia xanthochymus is observed to produce both male flowers and bisexual (hermaphrodite) flowers in clusters. The latter can be distinguished by their longer longer axils. The bisexual flowers apparently self-pollinate so that fruits can form.
Unlike what one of its common name ‘eggtree’ suggests, the fruit of Garcinia xanthochymus is not egg-shaped. The fruit has a curved pointed end which makes it look like an inverted tear-drop. Like the common mangosteen, one can find persistent sepals and staminal bundles even on a mature, ripe fruit of Garcinia xanthochymus.
Fruits produced by Garcinia xanthochymus are green when young and they turn bright yellow when ripe. They look extremely tempting and are often reported to have a juicy pulp with a pleasant acid flavour and can be eaten out of hand. I beg to differ on this as I find the pulp extremely sour and not pleasant at all! It is no wonder that the fruits can be used as a tamarind substitute in cooking. Another species, Garcinia atroviridis, bears fruits that are used in the same way. Inside each fruit, there are two brown, oval-shaped seeds.
The fruits of Garcinia xanthochymus are also made into preserves and jams and used for making vinegar. They can also be dried so that they can be stored for a longer time and used later. A sherbet made from the dried fruits is given in bilious condition. An inferior yellow coloured gamboge that has uses as a dyestuff is obtained tapping its stems or extraction from the fruit rind.
Garcinia xanthochymus is relatively easy to grow. Like many other Garcinia species, young individuals should be given shade when young. Plants should be given ample amounts of water during the hot and dry season. When established, this tree grows very vigorously and can adapt to a variety of soil types. It usually starts to produce fruits about 5 years after seed-sowing.
My contribution to the May 09 issue of the bimonthly Serangoon newsletter focussed on four selected beautiful flowering plants from the Acanthaceae family. The Acanthaceae family consists of numerous ornamental shrubs that feature rather long-lasting, showy and colourful inflorescences. The durability of inflorescences is due to the bracts and not the often insignificant, tubular flowers that the plants produce. Some members of this family of plants are also medicinal.
The four plants that were featured include the shrimp plant (Justicia brandegeana), lobster claw (Ruellia colorata), Golden Plume (Schaueria flavicoma) and lollipop plant (Pachystachys lutea). They can all be found growing in various parts of HortPark (NParks’ Gardening Hub for Singapore) such as the Home Garden and Golden Garden.
These four flowering shrubs should be grown in an area with direct sunshine for at least half a day that has soil that is fertile and well-draining. They will not thrive in waterlogged areas. Do also prune periodically when plants start to look straggly as this will help to ensure a compact and attractive growth form and rejuvenate them. Fertilise shortly after a hard prune to give plants a good kickstart again.
From what I have noticed, they fare better outdoors probably due to longer availability of direct sunshine. When grown in on a sunny balcony, plants can receive direct sunshine ranging from 4 to 6 hours daily. That is likely to be insufficient as apartment gardeners I have come across had lamented that their plants tend to grow rather straggly and etiolated and flower production had been poor.
Readers are to note there are some errors in the article due to my late returns to my Editor. The corrected article is shown above and its corresponding pdf file can be downloaded via the following link:
http://www.greenculturesg.com/articles/may09/acanthaceae_SGNL.pdf
Another Root Awakening column for the month of June 09 was published. This week, answers to three gardening questions were published.
The first enquired about white oil spray and how one can make some homemade pesticide spray for use on plants. White oil is basically is petroleum oil that is available in aerosol can form that is often applied as a leaf shine on plants. This oil can also be used in the same way like white summer oil (with emulsifier included) or super summer oil (without emulsifier) to control the populations of small sucking insects such as whiteflies, aphids, spider mites and mealy bugs upon contact.
A variety of homemade sprays can be made. The most common being chilli and garlic spray which can be concocted at home using some chillis and garlic pounded to yield a juice which is then mixed with some detergent and then sprayed onto plants. The insecticidal power of such a concoction is limited and is quickly washed away by rain and broken down by intense direct sunshine.
The second question dealt with the appearance of yellow leaves in hibiscus plants. It is a very common occurrence in Singapore and can be brought about by iron deficiency. One has to correct the underlying causes that led to this and this include excessively wet or compacted soil, root rot disease, nematodes or elevated soil pH. Feed with a water-soluble fertiliser that contains chelated iron. Phostrogen is a good one to try.
The last question was about distorted leaves seen on bird’s nest ferns and basil plants which I reckon could be caused by thrips or spidermites. These tiny pests like to attack the young and tender new leaves of many plants which go unnoticed by most gardeners due to their very small size. The damage manifests itself as distorted leaves when the affected leaves grow larger with time. Spidermites can be eliminated using repeated sprays of white summer oil but thrips can only be killed by using the more toxic and systemic pesticide called Confidor. The use of the latter is discouraged on edible plants such as basil.
The Indian lettuce is an edible leafy vegetable that is quite prevalent in Singapore’s community gardens. Botanically known as Lactuca indica, the Indian letttuce is a member of the daisy family, Asteraceae and related to the common lettuce (Lactuca sativa).
This vegetable is not available for sale commercially in Singapore and only the more senior gardeners are probably the ones who are familiar with it. They called it the “goose vegetable” (鹅菜) because the greyish green leaves were reportedly harvested and fed to geese several decades back when Singapore still had villages and farms.
Native to warmer parts of China, Taiwan and southern Japan, the Indian lettuce is thought to be introduced to this part of the world by Chinese immigrants. The plant is a perennial which sends up new shoots from the base of the plant. It adopts a rosette growth habit when young and depending on the cultivar, the leaves of this plant can range from simple, undivided to deeply pinnated. The one seen locally produces oblong-lanceoate in shape. There is a cultivar with prominent red mid-ribs.
With time, one will notice the leaf to leaf distance on the stem elongates and the leaves start to get narrower and shorter as well. When the plant attains a height of about 1.5 to 2 m, it will start to send up its inflorescence. The inflorescence is much branched and the daisy-like flowers each resembles a poached egg, complete with a yellow center and white rays. Growth terminates for that particular shoot and the plant spends its energy to produce seed. The plant sometimes sends up new sideshoots from the base.
Seedheads form after the flowers fade. One will be able to find numerous small and black coloured seeds loosely clustered around each seedhead. Each seed is flat, hard, black in colour and has some interesting-looking fluff that is attached to it on one end. With that characteristic, seeds of the Indian lettuce appear to be wind-dispersed. To grow this plant, one has to start from seeds but these are not available commercially as well. It is best to get fresh seeds by approaching a gardener who is growing some Indian lettuce plants in his/her garden.
The leaves of the Indian lettuce are not particularly nice to eat and are rather coarse in texture. When injured, the wound exudes a white latex. In my community garden, the Indian lettuce is grown like a cut-and-come-again vegetable where the leaves located lower down on the stems are harvested while leaving the plant to continue to grow. We do not uproot the entire plant for food. Besides being edible raw, steamed and boiled, Indian lettuce leaves have medicinal uses too. According to Plant Resources of South-East Asia (PROSEA), they are believed to possess tonic, digestive and depurative properties.
