Plectranthus rotundifolius Spreng.

Decumbent or ascending herb, 0.4-1 m; lower half of stem creeping, rooting from the nodes, and some of the roots swollen into sessile, oblong, 2-4 cm long, brownish black, aromatic tubers similar to small potatoes. Stem densely pubescent on the angles. Leaves thick-membranaceous, juicy, faintly aromatic when bruised, ovate to broadly ovate or suborbicular, 2-5(-6) by 1.5-3.5(-4) cm, rounded, base cuneate; margin elsewhere coarsely crenate; petiole 1—3(—5) cm. Terminal false spikes 5-15 cm long. Flowers 4-6 in a verticillaster. Pedicels 1-2 mm, puberulent. Bracts minute. Calyx campanulate; upper and lower teeth reflexed at anthesis; upper tooth oblong, acute, finely ciliate; median ones very short, with rounded apex; lower teeth highly connate forming an almost truncate apex, abruptly acute as 2 tips, widely apart. Corolla light or dark violet, 7-10(-12) mm long, tube strongly curved; upper lip very short. Filaments connate below into a tube enveloping the style.

A tropical plant. It suits high rainfall areas with an evenly distributed rainfall and low night temperatures. It is grown as a monsoonal crop. It needs a well drained, sand loam. It cannot stand water-logging. It is grown on ridges in heavier soils. It cannot stand cold or frost. It cannot tolerate drought. The best pH is 6.5-7.0. In East Africa it grows up to 2,200 m above sea level.

Uses. The white, starchy, slightly aromatic tubers become dark with age. They are eaten cooked or steamed, sometimes even raw; they are also mixed with sayor. Adult tubers are also used as a substitute for potatoes, for the preparation of minced meatballs. BURKILL ( BURKILL Dict. 1935 636 ) says they should be consumed in small quantities, as they are somewhat indigestible. HEYNE ( HEYNE Nutt. Pl. 1927 1335 ) says cultivation in Java is mostly in loose soil on fallow rice-fields, in West Java (Banten, Djakarta) and East Java (Bagelen, Kedum Jogja); harvested after 3-4 months. HARTLEY ( HARTLEY Lloydia 32 1969 265 ) listed it as a potential anti-cancerogene.

It is grown from suckers from germinating tubers. The tubers are put in a nursery bed about 4 cm deep and 10 cm apart. Tubers germinate in 10-15 days once watered. These produce a cluster of sprouts which are then transplanted after about 3 months. The earth is heaped up around the plants to encourage tubers. A spacing of 20 cm apart in rows 90 cm apart is used. It can also be grown from cuttings. Sections 10-20 cm long are used.