Traditional semilleros are simply plots of outdoor land where tobacco seeds are planted to germinate.  With traditional semilleros, the plants are exposed to direct sun and weather fluctuations, so there is less control over the growing conditions.  The result of using traditional semilleros is inconsistent plants and leaves.  This technique is only viable for filler tobaccos. 

Most premium cigar tobacco today is grown in semilleros which are protected and shaded from the direct sun and weather; what we call nurseries.  Modern cigar nurseries use elevated soil beds and individual containers to grow each plant.  Controlling the soil quality, water, and sun is imperative at this point.  In addition, covered semilleros also help control the germs and contaminants which can effect the plants: this is why there are small "shoe baths" for visitors to walk through at the entrances to the semilleros.  Cleanliness and control are imperative during the seedling stage while the plants are at their most susceptible and precious age.  Planting in semilleros allows farmers to control plant health and quality before they reach the fields.  Germination takes approximately 38 to 45 days, or until seedlings are 15-20 centimeters (6 to 8 inches) tall.  Infant plants are visited daily: the weakest, insect damaged, and least favorable plants are disposed of.  The seedlings shown in this video are approximately 25 days old.