Basil propagation is from seed but cuttings can also be planted. Commercial growers will plant basil seed by direct sowing or what is more common is to make seedlings in a protected environment or greenhouse and plant these out after three to four weeks.
Planting of basil seedlings and direct seeding is done by hand and mechanically. Direct sow 10 cm in the row to ensure a full stand of basil and thin out later to the desired plant density.
Plants should be spaced 30 cm apart in rows that are 50 cm apart. This is between 65 000 and 67 000 basil plants per hectare. Some commercial farmers increase plant density to 80 000 to 100 000 plants per hectare.
Sow basil seeds in early to middle spring making sure to miss the last frosts. In South Africa, this is late August to October.
Making basil seedlings in a greenhouse during July will gain a few weeks on production time. Plant the seedlings out when they are about 150 mm tall, just after the last frosts from late August to October.
From the time the basil seeds are planted to when the first harvest can be done is about ten weeks. Thereafter the basil can be harvested twice more. Cut the basil 15 cm above the ground allowing enough stem for re-growth.
Do not over fertilize as this will hasten maturity and flowering. Fertilize according to soil analysis done on the soil prior to planting. About 200 to 300 kg of 3:1:5 when plants are about 20 cm high should be ample until the first harvest. Apply the same after each consecutive harvest. Foliar feeds are also good to promote healthy leaves.
Basil is very sensitive to moisture stress so it is very important to keep the soil at the optimum capacity advised for the type of soil. Install moisture readers for constant monitoring. Stress will bring on flower, which is detrimental to production.
Basil can be irrigated by sprinkler or drip. Drip is, however, best as it keeps the leaves dry. Wet foliage can cause fungus growth, which damages the leaves. Depending on the weather and temperature basil can grow on about 40 mm of irrigation per week. It is advisable to spread this over two to three applications per week. On sandier soils irrigation could be required every second day. Mulching is advised as this lessens evaporation. Plastic or organic mulching can be used. This also controls the weeds.
By Louise Brodie