Preventing Cross-pollination Between Cannabis & Hemp

by | Mar 16, 2021

Written by Deborah Agboola

Robert Morf owns and operates Cheshire Creek, an outdoor Cannabis cultivation operation in Waterville, Washington. He stands to lose about $40,000 after hemp pollen from the neighboring hemp grower pollinated his Cannabis plants. He had given the hemp grower the OK in good faith that the grower would use clones, not seeds while thinking that either way, cross-pollination would be a bigger problem for the hemp grower than his Cannabis crop. Regrettably, it wasn’t so.

Cross-pollination in Cannabis and Hemp

Cross-pollination is a critical evolutionary process that allows for the recombination of genes and this is the main process used in creating new Cannabis and hemp cultivars. 

It is important to note that only plants of the same species or very closely related species can cross-pollinate. Even though Cannabis and hemp crops often have very disparate usages they are very closely related and can definitely cross-pollinate. For growers trying to create high-quality hemp or Cannabis flower, cross-pollination is a major threat.

The Natural Law

The number one objective for every species is to reproduce. Sexual reproduction is the most common form of reproduction in plants; a process that requires the exchange of genetic material, or simply put; pollination. Most plants are pollinated by wind, animals (often insects) or both. Cannabis and hemp are primarily wind-pollinated. Even with this natural process in mind, growers of hemp and Cannabis desire to optimize nature for our benefit; we want to control when and how cross-pollination happens.

The Problem with Cross-Pollination in Cannabis

When the 2018 Farm bill passed and industrial hemp cultivation became a reality, many cannabis growers were ambivalent. However, in areas where Cannabis and hemp area growing side by side, things are taking a horrible turn as a horde of angry cannabis growers are raising their pitchforks at the hemp growers.

Why? It seems hemp pollen has gone rogue—unfavorably pollinating female cannabis plants. 

In both sectors, cross-pollination can lead to massive losses. In the hemp industry, cross-pollinating with high-THC cannabis leads to the destruction of high-THC hemp harvests and total crop loss. And in cannabis, it can mean significantly reduced yields. 

In the 1970s, cannabis growers found that female flowers produce more and larger buds with higher amounts of cannabinoids when they remain unpollinated. And a 1998 study proves that pollination reduces the yield of essential oils in cannabis by 56%.

However, it is seemingly impossible to retain this efficiency if nearby hemp growers keep using male hemp seeds. The dangers that come with rogue cannabis pollen do not end there. Since the pollen contains DNA, it can transmit and infect other healthy plants as far away as five miles.

Fortunately, there are ways to avert these dangers, including channels for government assistance and facilitating technologies.

Solving the Problem

Understanding the factors that create opportunities for cross-pollination makes it easier to know how to prevent it. The following factors influence pollen/spore transport and viability:

  • wind speed
  • wind direction
  • precipitation and humidity
  • topography
  • physical barriers
  • time since release  

The industrial hemp regulations of the Association of Official Seed Certifying Agencies (AOSCA) state that a safe distance range, between 3 miles and 30 miles, must be kept between varied hemp pedigrees and cultivars. The Canadians also agree with this rule.

So for varying types like cannabis and industrial hemp, experts agree that a distance of 10 miles is sufficient between fields to avoid cross-pollination

The government can also enforce geographic isolation by allocating regions to cultivating the different cannabis types. But this rule is only enforceable – at the minimum level – by the department of agriculture and rural development.

Another solution is the use of feminized seeds in both cultivation operations. Most cannabis growers already use female cannabis. But for hemp farmers: female, male – it doesn’t matter unless they are growing them for seeds.

Other means to controlling cross-pollination include:

  1. Surrounding the cannabis plants with taller plants. Sunflowers trapping pollens grains is a proven effective technique
  2. The use of indoor cultivation systems is also applicable, though it is relatively cost-inefficient and might reduce yield. 
  3. Under indoor systems, HEPA filters can be easily integrated. By regulating air pressure, pollen can be kept at bay.
  4. Misting the male flowers via irrigation systems early in the morning may also help weigh down pollen. 
  5. The use of a staggered planting system may be efficient. However, this will only work with adequate communication, cooperation, and organization. This technique is based on structuring plantings in order of their growing season. So, by the time a harvest is ready, another cultivar is just flowering.

Pollen Sense Technology

Pollen Sense has developed a sensor that alerts growers in real-time of pollen and mold spore-related risks.

The Pollen Sense APS sensor uses automated microscopy and machine learning to identify and count airborne pollen grains and mold spores around the clock. The data gathered by the sensor is accessible to the operator via a web portal and the Particle Wise app, which notifies the operator of risks in real-time. The Pollen Sense web portal also offers a range of customization options. Users can customize reports and filter alerts to specific mold or pollen species. Raw images of impending risks are viewable in the portal to confirm the threats. 

The pollen notifications from Pollen Sense allow growers to turn on misting systems or employ other pollen mitigation techniques. When it comes to mold spore monitoring, growers can monitor for diseases and disease pressure. Prediction and early detection of fungal diseases make control much more effective and efficient. Since some disease spores are are ubiquitous growers can connect activities to the release of spores.

With Pollen Sense, the ability to detect risks early enhances the efficacy of other precautionary means enabling growers to remain a step ahead. 

To learn more about Pollen Sense, click here.