Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

characteristics of the “strain.” Perhaps “family” or “group” are more appropriate terms.
    Open Pollinated Varieties - Non-hybrid populations reproduced by random pollination within the variety. All pistillate individuals have the potential to mate with all staminate individuals as the pollen spreads randomly, ensuring preservation of the genetic diversity within the breeding population. In cannabis, open pollination is carried out by planting the breeding population together in a given plot isolated from other pollen sources and left to the will of the wind. To maintain varietal purity, hemp breeders ensure there is no non-varietal pollen source within four miles upwind, and one mile downwind-which should demonstrate just how far cannabis pollen can travel on the wind.
    Heirloom varieties/Heirloom seeds are the product of many years of selective planting and seed saving. The original seeds bore a plant or flower that had particular traits the grower liked–typically flavor, color, or psychoactive effect. The grower then saved the seeds from the desirable plant and repeated the process the next season selecting for similar type plants. The term “heirloom seeds” came about because the selection process for some cultivars has been going on for generations, often passed along within a family and/or shared with friends.
    Heirloom varieties are non-hybrid (open-pollinated). This simply means that they breed relatively true. Thus, growers can save seeds from their crops, plant them the following year, and expect to see offspring that are very much like the parent generation. Any off-types in each generation should be rogued out of the breeding population to keep it pure, as they are likely the result of pollen contamination from an external source.
    Multi-line - Two or more pure-breeding lines, which are very similar, but differ in a small partof the overall phenotype (i.e., maturation, disease resistance). The varieties are grown and bred separately but are subsequently mixed together and sold in the same seed package. These packs are a benefit to growers if the grower’s given environment is inconsistent from year to year, or for growers who are experimenting with growing in a new location. For example, a multi-line may include a slightly earlier-maturing variety with a slightly more mold-resistant variety; most other traits are equivalent in each population. The variations in performance of each variety with regard to mold or earliness of maturity ensure that there will be some harvest even in a year where only the early varieties finish (as a result of early rains), or even if mold is more prevalent during the particular grow season. If a grower is new to an area, multi-lines may be useful for the first few years of planting. It is always a shame to plant a single variety, only to find it is not suitable for the particular climate, thus wasting the year of production. The grower may not reap the highest yield as may be possible from a single hybrid variety particularly suited to the climate, but the degree of variation present in multi-lines helps to ensure at least some plants are harvested.
    Synthetic variety - an interbreeding population derived from intermating a group of specific genotypes, each of which were selected for good combining ability in all possible hybrid combinations. Subsequent maintenance of the variety is achieved by open pollination and usually involves rounds of recurrent selection over a series of generations.

Intersex plants are often mistakenly called hermaphrodites.
    Intersexuality Is a trait that can be expressed due to a multitude of causes, both genetic and environmental. There are intersex plants which are strictly genetic; these plants have inherited a gene that triggers the intersex condition, even given a perfect growing environment. They produce both pistillate and staminate flowers on the same individual under typical environmental conditions. Strict negative selection against these plants is required by breeders and growers in order to eliminate the intersex trait from the breeding population. Cultivators and breeders alike have wisely selected against plants that show the slightest degree of intersexuality. They know even a single male flower on an otherwise female plant can result in the majority of the crop being pollinated, and thus seeded.
    Indoors, where growers attempt to mimic Mother Nature, plants often undergo stresses which are not present under natural