Rosel

 

ROSEL 

Botanical Names

Hibiscus sabdariffa L. 

Common Names

Malaysia

Rosel, asam paya, asam susur, gamet.

English Roselle, sorrel.
Indonesia Rosela.
Thailand Bissap.
India Mestal / meshta.
Myanmar Krajeab.
China Luo shen hua.

Family

Malvaceae

1_Roselle
‘Rosel’ fruits at optimum maturity ready for harvesting

Introduction

There are more than 300 species of ‘rosel’ throughout the world especially in the tropical and subtropical regions. It can be found in India, Africa and Asia including Malaysia. In Malaysia, it is commonly planted as a household herb and as an ornamental. Commercial cultivation of ‘rosel’ was started in 1993 by the Department of Agriculture Malaysia.[1][2]

Morphological Features

‘Rosel’ plant is an annual, 2-2.5 m tall, with lobed leaves and has many branches. The leaves are green while veins, petioles and stems are red. The stems grow upright initially but then droopy as they become heavy with fruits. ‘Rosel’ flowers are pink and the fruits are red. They develop and mature progressively starting from bottom nodes upward. The fruit is made up of fruit petals called calyx that surrounds an oval seed pod at the centre.[1][2]

Medicinal Properties and Usage

The main edible part is the calyx. It is fleshy, bright red and sour in taste. It is rich in vitamin A and C as well as high in potassium and calcium contents. Calyces can be processed into cordial, juice, jam, snack and other products. Traditionally, ‘rosel’ is widely used globally for medicinal purposes as well as for food flavouring. The dried calyces are used as herbal tea. Drinks made of calyces or leaves are believed can improve blood circulation, reduce blood pressure, improve digestion and also having antibacterial and rejuvenating effects. The oils extracted from seeds are processed into cosmetic products.[1][2][3][4]

Soil Suitability and Climatic Requirement

In Malaysia, ‘rosel’ grows well on most soils from sandy loam to sandy bris or other soils with good drainage. However, it is not suitable on clayey or poorly drained soils. The plant is not suitable for wet season planting since diseases easily infest it.[1][2]

Field Preparation

Land Preparation

Normal operation such as land clearing, disc ploughing and rotovation are conducted. If the soil is acidic (pH is less than 5.5), liming using Ground Magnesium Limestone (GML) at the rate of 2-4 t/ha is done at least two weeks before planting. Field drainage system also needs to be established to avoid waterlogged problem after heavy rain.[1][2]

Production of Planting Materials

‘Rosel’ is propagated by seeds as the seeds can be easily obtained from mature fruits. The collected seeds are usually used for the immediate season planting since seed quality easily deteriorates with storage. Prior to planting, seeds are sown in seedling trays. After 14 days, the seedlings (15-20 cm tall) are ready for field planting.[1][2]

Field Planting

In areas where flash flood is pertinent, planting is done on raised beds. ‘Rosel’ seedlings are planted at a distance of 150 cm between rows and  60 cm within row which is equivalent to 11,110 plants/ha. Large scale planting can be mechanised.[1][2]

2_Rosel_G21
Planting of ‘rosel’ by transplanter

 

3_Roselle
Fruiting ‘rosel’ crops on bris sandy soil

Field Maintenance

Fertilisation

For sandy bris soils, organic fertiliser or soil amendment such as chicken manure at 10-20 t/ha or POME at 20-40 t/ha are used to improve soil fertility. For mineral soils, only half of the rates are recommended. The fertiliser is applied and mixed into the soil 5-7 days before planting Inorganic fertiliser at 350 kg/ha (NPK=15:15:15) is given at the early growth stage. While at the flowering stage onward, the rate is 1,200 kg/ha (NPK=12:12:17:2). The rate of inorganic fertiliser is reduced by 10-30% for mineral soils.[1][2]

Weed Control

Weed problem can be overcome by using pre-emergence herbicide at planting. Then after 40 days or as the plants are tall, it is followed by a single round of roto-tillage operation. Later on, the weed is controlled by careful sprays of contact herbicide.[1][2]

Water Management

A supplementary irrigation system is needed to provide optimum water supply to the crop throughout the growing period. Sprinkler or rain-gun irrigation system is suitable to be used on ‘rosel’ crop. Excessive irrigation must be avoided to avoid disease problem and to minimise nutrient losses as well.[1][2]

Pest and Disease Control

Green plant hoppers (Nephotettix sp.) and stink bugs (Dysdercus cingulatus) are the main pests for ‘rosel’ crop. The pests are controlled by spraying insecticides such as imidacloprid or deltamethrin. On the other hand, Coneilla musaiaensis and Phoma sp. are the main diseases, and can be controlled by spraying fungicides such as carbendazim or mancozeb. These diseases are only serious when the crop condition is hot and wet.[1][2]

Harvesting

Harvesting of ‘rosel’ fruits is done 6-9 times with 7-10 days intervals beginning at 70 days until 140 days after planting. The fruits are plucked individually and only full-grown fruits are harvested. At this stage, the calyces are still tender and the seeds inside the seed pods are still whitish in colour. Harvesting operation is done manually and very labour intensive. The fresh fruit yield is 12-25 t/ha depending on soil types and cropping seasons.[1][2][5][6]

4_Rosel_G28
Harvesting of the fruits by using scattier

Postharvest Handling

To ensure freshness and good quality, harvesting is done in the morning. Fruit injury and contamination of foreign materials are strictly avoided. While in the field, the harvested fruits must always be kept under shade. The fruits are quickly sent to collection centre for further operations such as washing, grading, removing seed pod and storing in cool storage rooms awaiting processing.[1][2]

5_Rosel_G30
Separation of seedpod from the calyx

Estimated Cost Of Production

The total production cost for a ‘rosel’ crop is estimated at RM10,800/ha. It is made up of RM5,260 for agricultural inputs, RM4,200 for labour, RM360 for contract and RM980 for other costs. Thus, the production costfor a 16 t/ha of fresh fruit yield is RM0.70/kg. The production cost was estimated based on the cost of current inputs during writing of this article.[1][2]

Read more

1) Botanical info

2) Safety

3) Western Herbs

References

  1. Engku Ismail, E.A, Musa, Y. and Yahaya, H. (2005). Rosel (Hibiscus sabdariffa). In: Penanaman tumbuhan ubatan & beraroma. (Musa, Y., Muhammad Ghawas, M. and Mansor, P., ed.). Pg. 77-82, Serdang: MARDI
  2. Musa, Y., Engku Ismail, E.A. and Yahaya, H. (2006). Manual penanaman rosel. Serdang: MARDI
  3. Anon. 2002. Compendium of Medicinal Plants Used in Malaysia (Vol. 2) Pg 14, Kuala Lumpur : HMRC-IMR
  4. Kamarudin Mat-Salleh and Latiff, A. (editor). 2002. Tumbuhan Ubatan Malaysia. Pg.  248, Kuala Lumpur : UKM
  5. Engku Ismail, E.A. and Zaharah, A. (1996). Prestasi tanaman roselle di tanah bris, siri Baging. Proceeding Seminar Penyelidikan Tembakau ke-18, 17 Dis. 1996, Kangar, Perlis. Pg. 187-198, Serdang: MARDI
  6. Yahaya, H., Zaharah, A., Azmi, R. and Salma, O. (2001). Tanaman giliran dan tanaman alternatif di tanah bris. (Occasional Paper No. 1/2001). Serdang: MARDI.