With the amazing South African sun and environment to grow outdoor cannabis, why is indoor cannabis still much denser and more flavorful?
A big factor is genetics. Genetics plays a vital role in the chemical makeup of your cannabis plant. Outdoor cannabis needs to have strong genetics in order to survive the elements throughout the flowering period. Some plants are good at dealing with the wind, rain and temperature fluctuations, but others are not. Land-races, or hybrids containing land-race genetics are your best bet for growing outdoors because natural selection has already done a large part of the work. The problem with using these land-races is that they have not been bred with cannabinoid and terpene production in mind, but rather yield being the primary focus.
When growing indoor, you have a long list of genetics to choose from with more strains coming out everyday. Each strain will have a preferred environment in which it will thrive, and you will have the control to keep it in that environment. Humidity and temperature are of huge importance when trying to maximize density and flavors. Although cannabis enjoys warmth and humid air when it is in it's vegetative state, the flowering state prefers the opposite.
Ideally, in South Africa, you would want to utilize the powerful African sun while keeping the humidity and temperature controlled in a greenhouse. If you can add lights and light deprivation (depending on season) to control the hours of light, then you will essentially be growing indoor, outdoor.