Whether you are planting a winter or upcoming spring crop, re-seeding or enhancing a stand of Conservation Reserve Program (CRP) or State Acres for Wildlife Enhancement (SAFE), or simply interested in seeing if a winter,… 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. How to Tell if a Cannabis Seed is Good Got a cannabis seed, but you’re not sure if it’s any good? No worries. By the end of this article you’ll know everything you need to get started. The
Is Your Seed Dead or Alive – A Seed Viability Test
Whether you are planting a winter or upcoming spring crop, re-seeding or enhancing a stand of Conservation Reserve Program (CRP) or State Acres for Wildlife Enhancement (SAFE), or simply interested in seeing if a winter, spring or possible summer cover crop planting will help the overall health of your soil, it is important to make sure the seed you plan to use is viable.
A “Seed Tag” usually accompanies seed purchased from seed companies. This tag tells the buyer several things: 1) what variety and species is in the bag, 2) a lot number which tracks where the seed was produced, and 3) information such as the percent purity, percent inert material, percent weed seed, percent noxious weed seed and percent total germination.
Unfortunately, not all seed comes with a tag. Any seed that has been set aside from harvest to be planted for next year’s crop will not have this information. One- or two-year-old seed should be fine to plant, but what if a producer had some seed from 10+ years ago that they wanted to use?
Fortunately, there is a simple way to test seed viability.
You will need:
- A petri dish (plastic, shallow, flat, clear dish) or a ziplock bag
- A lid for the petri dish
- A paper towel
- Plastic wrap
Then, you’ll follow these five simple steps:
- Moisten a piece of paper towel with water and place it in the petri dish;
- Evenly place 10 or more seeds on the paper towel. You may want to fold the towel over the seeds so both sides of the seeds are moist;
- Place the lid on the dish and wrap tightly with plastic wrap;
- Place in a warm environment (i.e., kitchen counter); and
- Wait for 7 to 10 days, then check the dish for seeds that have visibly germinated (i.e., sprouted) and count them.
The percentage of germinating seed also known as pure live seed (PLS) will give you a fairly good idea how that same seed should perform when planted provided the seed receives adequate moisture. Adjust seeding rates based on the percentage of germinating the seed.
Species: Eltan WW
Desired seeding rate: 12 seeds/ft row or 50 lbs. /A on 12-inch spacing (St. Andrews Variety Trial Seeding Rate)
The seeding rate of bulk seed: 50/0.80 = 55.5 pounds of bulk seed
Therefore, you will need an additional 5.5 lbs/acre of seed to reach either the desired 12 seeds/ft row or 50 lbs/acre based on a PLS of 80%.
For help with converting lbs/acre to seeds/ft row, lbs/acre to seeds/acre or vice versa for both, please visit our Crop Tools & Calculators page and check out the Seeding Rate Converter calculator.
For questions or comments, contact Dale Whaley by email at [email protected] or by phone at 509-745-8531.
Fate of weed seeds in the soil
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.
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.
Results: The emergence patterns of the four species were described in an earlier article (see emergence patterns). The fate of the seeds (emergence, loss or survival in soil) during the first four years after burial is shown in Figure 1. In the first year following burial waterhemp had the lowest emergence (5%) whereas greatest emergence was seen with woolly cupgrass (40%). Total emergence over the four years ranged from 300 seedlings (15% of seed) for waterhemp to 1020 seedlings (51%) for woolly cupgrass. More than three times as many seedlings emerged in the first year than in subsequent years for velvetleaf, woolly cupgrass and giant foxtail, whereas 140 waterhemp seedlings emerged in 1996 compared to only 100 in 1995.
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.
Seeds of the two grass species were shorter lived than those of velvetleaf or waterhemp. At the end of the third year (1997) no grass seeds were recovered. Somewhat surprising is that waterhemp seed was more persistent than velvetleaf in this study. Velvetleaf has long been used as the example of a weed with long-lived seeds. In the fourth year of the study four times more waterhemp seedlings than velvetleaf emerged and four times more waterhemp seed than velvetleaf seed (240 vs 60) remained in the seed bank.
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.
So what does this mean as far as managing weeds in Iowa. First, consider how the methods used in this experiment might influence the results. The seeds were buried in the upper two inches of soil, the zone most favorable for germination. Most long term studies investigating the persistence of seeds have buried the seeds at greater depths than used here in order to minimize germination. If the seeds were buried deeper one might expect less emergence and greater persistence since the seeds would be at a soil depth with less biological activity. If the seeds had been placed on the soil surface it is likely that there would be more predation, less emergence and shorter persistence.
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.
Doug Buhler is a Research Agronomist at the National Soil Tilth Laboratory, USDA/ARS, Ames, IA.
How to Tell if a Cannabis Seed is Good
Got a cannabis seed, but you’re not sure if it’s any good? No worries. By the end of this article you’ll know everything you need to get started.
The legality of growing cannabis varies depending on where you live in the world. Know your laws.
What to Look for in a Healthy Cannabis Seed:
You can tell a lot about a seed’s health just by looking at it. Here are a few different things you should look for when deciding if a cannabis seed is good or not.
- Darkened Color – Good cannabis seeds will be brown, black, and/or gray. White or green seeds are immature and unlikely to sprout. Your seed should also have stripes or spots all the way around.
- Waxy Coating – A healthy seed will have a thin waxy coating around it. This coating should appear to have a slight sheen to it.
- Hard Shell – You should be able to lightly squeeze a seed without it crushing. If a seed crushes easily between your fingers then the seed is likely dead or weak and will not grow well.
- No Cracks – Inspect the entire seed to make sure there aren’t any small crack or holes. This will most likely cause the seed not to sprout.
Ways To Test Cannabis Seeds
Now that I’ve gone over a basic guide for what to look for I’ll give you a couple of ways that you can test your seeds.
Test Method #1: Floating Seeds in Water
This is a great test that works for many different seeds – not just cannabis. Take your seeds and drop them in a cup full of warm (not too hot) water then wait a couple of hours. If they sink then they’re probably good to go. If they won’t sink then they are probably dead and won’t grow.
Note: Only do this if you’re ready to germinate your plants. Otherwise, it could harm your seed. I cover germination in a later section.
Test Method #2: Just Go Ahead and Try to Germinate the Seed
I know this seems obvious, but it really is the best information I really could give. If you really want to know if a cannabis seed is able to germinate then go ahead and try germinating it – what do you really have to lose? Not quite sure how to germinate a seed? No worries. Here’s a quick guide:
How to Germinate a Cannabis Seed
Germinating a seed simply means getting the plant to sprout from the seed. It’s the first step in your cannabis seed’s journey to a full grown plant. There are several ways to go about this.
One way is to simply plant it in your soil and see if a plant pops up. It’s old school, but no one can deny its simplicity. Plant the seed about 1/4″ deep and wait.
Another way is to put the seeds on a damp paper towel. Make sure the paper towel is damp, but not soaking wet. If it dries out you can add a few drops of water to the paper towel. Leave the paper towel in a dark place. The amount of time is going to vary among strains. Some may take only 2 days while others could take longer. Continue to check them once a day.
How to Tell if a Cannabis Seed is Male or Female
Unfortunately, there is no way to know if a cannabis seed is going to be male or female simply by looking at it or doing a simple test. This is a bummer since most people don’t want male cannabis plants in their garden.
If you want feminized seeds then you’ll have to buy them from a reputable seed bank. Make sure they say feminized – if they don’t say it then they probably aren’t.
If all you’ve got is a bag seed then the only way to find out if it’s going to be male or female is to grow it.
Can My Cannabis Seed Go Bad / Expire?
The short answer is yes, but if you store your seeds properly they can stay viable for years and years. Moisture, UV degradation, and extreme temperatures could all affect the quality of your seeds.
If you plan to store your seeds for a long period of time make sure to keep them in an airtight container in a dark area. Ideally, seeds should be stored in a climate controlled area (like inside your house instead of in a shed or garage. One study showed laboratory-sealed cannabis seeds were still viable after 19 years.
It’s nice to know what to look for, but in the end the best test is just to put it in soil. If you’re using bag seeds then you never really know what you’re getting anyways. If you’ve bought your seeds from a legitimate seed bank then you shouldn’t have to worry about it.