The international trade of roselle calyces has increased steadily, with 15,000 tons/year in the world market. Germany and the USA are the top importers. In the Philippines, there is very little published information on both the areas in which roselle is cultivated, or on the production levels of roselle, although some portions of Metro Manila, Visayas, and Mindanao have dried calyces, wines, and other processed products in local markets and even online.
USES AND NUTRITIONAL VALUE The leaves and calyces serve as a souring agent (mostly as a substitute for vinegar) for some popular Filipino dishes such as ‘sinigang na isda’ and ‘sinaing na tulingan’. In the Ilocos region, roselle seeds are grilled, ground, and brewed for coffee.
Roselle calyx is used in jams, jellies, sauces, syrup, gelatin, and wines. The calyx is also used for making a refreshing beverage called ‘jamaica’ in Mexico. Dried calyx is used for tea, jelly, marmalade, ice cream, sherbet, butter, pies, tarts, and other desserts.
Roselle stems are used for fuel and fiber while the whole plant is used to treat various ailments; the plant itself is considered ornamental. Roselle leaves have high levels of polyphenol compounds (chlorogenic acid and its isomers, quercetin and kaempferol glycosides), which may contribute to its antioxidant properties and anti-inflammatory activities.
Roselle infusions are a very popular drink in many parts of the world. Its phytochemical composition is associated with anti-oxidant, anti-hypertensive, antidiabetic, and anti-atherosclerotic (clogging or hardening of the arteries caused by accumulations of fatty deposits, usually cholesterol) effects.
NUTRIENT MANAGEMENT Roselle requires minimal management and production inputs. Fertilizer application (usually compost or other organic inputs at the rate of 0.51.0 kilograms or kg/ per square meter or m2) can be done as basal or side-dressing once or twice during the vegetative stage and once during the reproductive stage.
It has a deep root system, which contributes to its drought tolerance. It can compete well against weeds, though higher calyx yields can be obtained if weeding is practiced.
PRODUCTION MANAGEMENT Varieties: There are many cultivars or lines of roselle based on phenotypic variations in plant height, color of leaves and calyx, size of calyx, yield and taste of the calyx. However, there are still no recommended varieties for leaf, calyx or fiber production.
Propagation and planting: It can be propagated through seeds and stem cuttings. For leafy vegetables, seeds can be directly sown or transplanted 2 weeks after sowing in 5meter or m x 1m plots with 50 centimeter or cm x 20-40 cm planting distance and 2-3 plants/hill.
Planting distance for calyx production should be wider, up to 100 cm apart. It is important to note that timing of planting is a critical aspect, especially in calyx production. Since roselle is a photoperiod (i.e. change in day length) sensitive plant, planting should be done by October so that flowering will commence during the cold months.
PEST MANAGEMENT Diseases commonly observed in roselle include leaf spot, caused by Cercospora hibisci, and powdery mildew ( Oidium abelmoschi). Roselle with green leaves appear to be more susceptible than the red leaf types. Phytophthora spp. causes stem burn and the sudden wilting of the plant. Spraying roselle with compost tea can reduce downy mildew infestation and other diseases.
Insect pests can damage the leaves; these include the flea beetle (Podagrica spp.), calyx (cotton bollworm larvae, Earias biplaga/ insulana), cotton stainer ( Dysdercus supertitiosus) and stem (spiral borers, Agrilus acutus). Spraying the plants with a soap solution infused with hot pepper can help reduce insect pests.
HARVESTING AND PROCESSING For leaf production, leaves can be harvested 8 weeks from transplanting, and this is usually done 2-3 times during the vegetative stage. For calyx production, calyces can be harvested 10-14 days after flowering, or when the calyx snaps off easily by hand.
Separate the calyx from the fruit, either manually or through the use of a cork borer prior to drying in the shade for 2-3 days. Yields of up to 1 ton or t/hectare or ha of calyces have been reported in Sudan.
POTENTIAL Aside from its potential as a vegetable crop, roselle is gaining attention nowadays from the food, beverage, and pharmaceutical industries because of its potential as a natural food product and as a colorant to replace some synthetic dyes. The calyx has big potential in the market, especially if processed (dried, jams, jellies, wines, health drinks, etc.).
RECIPES • Sinaing na tulingan with roselle leaves: Mix garlic, onion, ground black pepper, ginger, and water in a pot. Place roselle leaves under tulingan and let it boil for 30 minutes. • Roselle juice/tea: Steep 5-7 dried calyces or 2-3 fresh calyces in boiling water for 5 minutes or until the red color comes out. Serve warm or with rice.
For more information, please contact Dr. Rodel G. Maghirang, Crop Science Cluster-Institute of Plant Breeding, College of Agriculture, University of the Philippines Los Baños, 4031 College, Laguna, or email firstname.lastname@example.org.