Figure 1. Fate of seeds during the four years following burial in the upper two inches of soil. Two thousand seeds of each species were buried in the fall of 1994. The area in white represents the number of intact seeds present in the fall of each year, green represents the total number of seeds that produced seedlings during the four years, and the blue represents the total number of seeds lost. Buhler and Hartzler, 1999, USDA/ARS and ISU, Ames, IA.
The fate of weed seeds in the soil has been an area of much research in recent years. Most studies have focused on the seeds that successfully produce seedlings since these are the seeds that cause immediate problems for farmers. In most studies, annual emergence typically accounts for 1 to 30% of the weed seed in the soil. Thus, the majority of seeds found in the soil seed bank fail to produce seedlings in any given year. The fate of seeds that fail to germinate and emerge is poorly understood. While some of these seeds are simply dormant and will remain viable until the following year, others are lost due to decay or consumed by insects or small animals. This article will describe results of an experiment that monitored the fate of seeds for the first four years following introduction into the soil.
For all species except woolly cupgrass the majority of seeds were unaccounted for (the blue portion of the graph) in this experiment. Determining the fate of the ‘lost’ seeds is a difficult task. A seed basically is a storage organ of high energy compounds, thus they are a favorite food source of insects and other organisms. In natural settings more than 50% of seeds are consumed by animals. The importance of seed predation in agricultural fields is poorly understood, but recent studies have shown that predation can be a significant source of seed loss. Another important mechanism of seed loss likely is fatal germination. This occurs when a seed initiates germination but the seedling is killed before it becomes established. Fatal germination probably is more important with small-seeded weeds such as waterhemp and lambsquarters than with large-seeded weeds, but is poorly understood. A better understanding of the factors that influence seed losses might allow these processes to be manipulated in order to increase seed losses.
The results indicate that the seed bank of giant foxtail and woolly cupgrass should be able to be depleted much quicker than that of the two broadleaves. Maintaining a high level of weed control for two years should greatly diminish populations of these weeds in future years and simplify weed management. Unfortunately, a single plant escaping control can produce more seed than was introduced to the soil in these experiments, thus the seed bank can be rapidly replenished any time weed control practices fail to provide complete control. Finally, over 50% of velvetleaf and waterhemp seed was lost in the first two years following burial. However, significant numbers of seed of these species remained four years after burial. This will make populations of these two species more stable over time than those of woolly cupgrass and giant foxtail.
Methods: Seeds of velvetleaf, waterhemp, woolly cupgrass and giant foxtail were harvested from mature plants during the 1994 growing season. The seeds were cleaned and counted and then buried in the upper two inches of soil on October 21, 1994. Two thousand seeds were buried within a 3 sq ft frame to allow recovery during the course of the experiment. Weed emergence was determined by counting seedlings weekly during the growing season. Emerged seedlings were pulled by hand after counting. In the fall of each year one quarter of the soil within a frame was excavated and the remaining seeds were extracted and counted. Corn or soybeans were planted between the frames during the course of the experiment to simulate agronomic conditions.
If you’re going to try growing with seeds, check on their viability first. Seeds that are dark in color are best. Whole dark, mottled seeds are mature and ready to plant, but the lighter, softer or cracked seeds are not as viable for successful germination . The image below is an example of healthy looking cannabis seeds that should be viable.
If you are growing cannabis and are here to figure out if you have a male, female or a potential hermaphrodite: we want to introduce you to “ nanners ” which is a tell tale sign that pollination has taken place. Check out this article about how soon you can tell the sex of your cannabis plant.
The other option is that the plant has self pollinated. This is rare but that still does happen. This self pollination usually happens when the plant is stressed while undergoing the budding phase but sometimes it can manifest because of genetics or light leak during necessary dark times. This is often referred to as a hermaphrodite plant.
Saving the Seeds
You don’t want to spend your hard-earned money, come home ready to relax with your latest weed purchase, only to find that it’s full of seeds and not worth the money you invested. That said, even if you haven’t had the misfortune of buying weed full of seeds, it’s good to know the difference between good and bad weed, with or without a pesky seed invasion.
If the male is not removed in a timely fashion your female plants could become pollinated and start growing seeds. These seeds are part of the natural process and can be used to start a new grow. Careful, 50% of them will be males! Did you also know that cannabis seeds are a superfood? You can survive by eating just seeds!
Why This Matters
Purchasing weed with no seeds in it will get you better quantity and quality for the money you invest. The highest quality and most potent form of weed is that with no seeds. This weed is called Sinsemilla .
If you’re feeling ambitious you can take the seeds out of your pot and try to grow from them. Here are a couple tips for determining whether or not to grow with the seeds you find: