Coleus (Solenostemon rotundifolius) also known as Chinese potato, frafra potato and Hausa potato is among the lesser-known and underexploited tuber crop from the Western Africa. Although it has been cultivated and maintained by traditional farmers, there are no records indicating when it was first brought under cultivation; and also, it has not received sufficient attention from the scientific community in the past. The crop belongs to the family Lamiaceae. It is a small herbaceous annual crop with prostrate or ascending succulent stem and branches. The crop usually grows up to 20–30 cm in height. The tips of the adventitious roots modify into small round tubers. Unlike other tuber crops, this is a transplanted vegetable. The tubers contain 20-24 % starch.
Climate and Soil
Coleus thrives well in tropical and subtropical regions. The optimum temperature for growth and development ranges from 25-300C. A well-drained medium fertile soil with a pH range of 5.5-7.0 is suitable for its cultivation.
Coleus is usually cultivated as a monocrop but may sometimes be intercropped with yam, okra, maize, rice, sorghum, cowpea and groundnut. It is usually grown on ridges and sometimes on mounds but not on the flat. Tubers are mostly used for propagation but softwood stem cuttings can also be used. Plant the cuttings in the main field between July and October.
Varieties: Nidhi, Sree Dhara and Suphala.
Raise the nursery approximately one month before planting. An area of 500 to 600 m2 is sufficient to produce cuttings required for one ha of main field. Apply 125 to 150 kg FYM in the nursery area. Plant the seed tubers at a spacing of 15 cm on the ridges taken 30 cm apart. About 170 to 200 kg of tubers is required to raise the nursery. Take the vine cutting to a length of 10-15 cm from the top portion after three weeks from planting.
Plough or dig the land to a depth of 15-20 cm and form ridges at 30 cm apart or raised beds of 60-90 cm width. Plant the vine cutting collected from the nursery on ridges at a spacing of 30 cm or on raised beds at 30 x 15 cm spacing.
Broadcast 10 tonnes of FYM and N:P2O5:K2O @ 30:60:50 kg per hectare and incorporate into the soil at the time of land preparation. Top dress with N and K2O at the rate of 30 and 50 kg/ha respectively at 45 days after planting.
Give weeding and earthing up, at 45 days after planting along with topdressing. Cover a portion of the vine with soil to promote tuber formation.
To control the root-knot nematode, plough the field deeply in summer, adopt crop rotation and destroy root residues and other plant parts by burning. White flies (Bemisia tabaci), leafhoppers, termites, grasshoppers/crickets and millipedes are also associated with the crop.
Harvest the crop 5 months after planting. Drying up of entire plant indicates the maturity of the tuber. The tuber yield ranges from 18-20 tonnes/ha.