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female marijuana plant with seed pods

The vast majority of cannabis growers cultivate the plant to produce sensimilla . Sensimilla refers to female cannabis buds that have not been pollinated by a male cannabis plant. Sensimilla is more potent than seeded cannabis as it contains greater concentrations of essential oils and psychoactive cannabinoids.

Herming can also have a genetic component, with some growers viewing plants that are inclined to herm as genetically inferior.

How can growers prevent hermaphroditic plants?

Cannabis plants are gendered, or for the botanically-inclined, dioecious. Female plants are particularly prized because they form buds that are rich in cannabinoid content. For most growers, maintaining a crop free of male plants is critical to ensuring that female buds are not pollinated.

Author Robert Connell Clarke’s book Marijuana Botany An Advanced Study: The Propagation and Breeding of Distinctive Cannabis presents clear instructions for differentiating male and female plants. The gender of a cannabis plant is located at the nodes along the main stem.

Female plants are generally shorter, denser in foliage, and broader than their male counterparts. Photo by: Gina Coleman/Weedmaps

There is a good reason why most growers keep male plants away from their ladies: Pollination from males causes the females to develop seeds. As a result, females focus their energy on seed production, rather than on growing you some fine-quality bud. This seedy and unfortunate final product can be avoided by implementing a few basic techniques.

The typical cannabis grower normally doesn’t have a reason to keep males, and will want to get rid of them as soon as they are spotted. Cannabis breeders, on the other hand, may want to keep males along with their crop of female plants. In such cases, the breeder will normally separate the sexes to avoid any accidental pollination. They may grow females in one tent and males in another. When grown outdoors, such as in a garden, the males are often kept in the most remote corner of their growing area, as far from the females as possible. Even then, because of the wind carrying around the pollen, there is always some risk of accidental pollination.

HOW TO TELL THAT A FEMALE PLANT HAS BEEN POLLINATED

A good test to see whether the bracts have swollen is to take a pair of tweezers, grab one bract, and open it up. If there is a seed inside, you have a pollinated plant.

Male plants won’t show hairs at these nodes, but will develop little sacs of pollen. These pollen sacs will look like little balls. These balls can appear on their own or in clusters, depending how far into the pre-flowering stage the plant is. At some later stage of growth, the pollen sacs will burst open, spilling the pollen and possibly pollinating your females.

Another indication of pollination can be the colour of her pistil hairs. When a female has been pollinated, the previously white hairs will soon shrivel and become darker.

The bracts have the densest covering of capitate-stalked resin glands of any plant part, and it is within the heads of these resin glands that the plant synthesizes and holds the highest concentrations of cannabinoids and terpenes of any plant part. Bracts make up most of the substance and weight of high-quality marijuana buds.

The other two non-glandular trichomes are visible with magnification. These smaller cystolith hairs with warty bumps and teardrop-shaped trichomes are found mainly on the underside of leaves. The larger cystolith hairs provide defense against insects and likely make the plant less palatable to animals. Cystolith hairs also reflect radiation, reduce water loss, and ameliorate near-surface temperatures.

Stigmas are the pollen catchers. Some writers identify stigmas as pistils, and this too is incorrect. The pistil is all of the reproductive female flower parts. The Cannabis pistil consists of two stigmas and an ovule (prospective seed). The term is misused in many books and seed catalogs that describe a single Cannabis flower as having two pistils.

Bulbous glands are tiny, are present on the first leaves to form, and are found on stems, branches, leaves, and flowers. Although ubiquitous, their contribution to the overall cannabinoid concentration at harvest is insignificant.

If a flower is pollinated, the ovule becomes a single fruit, essentially a single seed, an achene. The perianth tightly clasps the seed and usually contains tannins, which give mature seeds their markings or spotted coat. Between a thumb and finger you can rub the perianth off of a seed.