Propagation is from seed but oregano can also be propagated by planting cuttings or dividing the established plant and planting this out.
Planting of oregano by large commercial growers is more commonly done by planting seedlings that have been produced in a greenhouse. The seeds are planted into seedling trays about eight to ten millimetres deep. Once the seeds have germinated and strong seedlings have grown these are planted out into the field.
Oregano plants should be spaced 30 cm apart in rows that are 50 cm apart. This is a stand of around 60 000 plants per hectare. Implement and tractor paths are left for management practices and harvesting.
Sow oregano seeds into seed trays in a protected environment or greenhouse during June and by early spring the seedlings should be strong enough to plant out into the fields.
Plant the oregano seedlings in early spring. In South Africa, plant seedlings in late August to early September.
Eight weeks in the greenhouse should produce strong oregano seedlings that are ready to plant out. For fresh oregano production, some producers start harvesting the fresh growth tips from as early as eight weeks from planting out.
Thereafter a further two harvests can be done before winter sets in. The second year of harvesting can yield five to six cuts. Oregano plants can be harvested for up to five years if managed properly. Plants do start to lose their potency as they get older so it is advisable to replace the plants every four to five years.
Before planting oregano, a representative soil sample should be taken and sent for analysis. This will identify soil type and nutrient requirements for the intended crop.
For a rough guide, the following recommendation can be used in the absence of soil analysis. An initial 450 kg application of 3:1:5 can be broadcast and incorporated into the top 20 cm of soil prior to planting the oregano seedlings. This will give the new seedlings a good start in establishing themselves. During the first 12 months, it is important to keep the plants growing so a further two applications of 300 kg of 3:1:5 can be applied along the plant rows, one in December and another in April. It is advisable to fertilize after every harvest cut.
Although the oregano plant is a hardy plant, moisture stress will stunt growth and reduce foliage production. Over-irrigating will cause root diseases, anaerobic conditions and reduced essential oil production and quality.
It is best to install moisture monitoring devices to continuously monitor the soil. Depending on soil types and the weather, irrigation volumes will differ from field to field. A good average is between 25 and 30 mm per week during the warm summer months and reducing during cooler or rainy months of the year. Do not water for the week before harvest, but irrigate immediately after harvest to bring soil back to optimum moisture levels and to minimize stress.
By Louise Brodie