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how long to soak cannabis seeds

Soaking Seeds: A How-To

Sometimes it seems to take forever for seeds to germinate. Want to speed up the process? Try soaking them first.

Soaking seeds before planting is an old-time gardener’s trick that many new gardeners are not aware of. When you soak seeds before planting, you can significantly decrease the amount of time it takes for a seed to germinate. Let’s look at the reasons for soaking seeds and how to soak them successfully.

Reasons for Soaking Seeds

What happens to seeds when you soak them? Why should you soak your seeds? The short answer is because your seeds were designed to be abused. Mother Nature is not kind to a little seed. In the wild, a seed can expect to encounter harsh heat and cold, wet or dry conditions and may even need to survive through the acid-filled digestive tract of animals.

In short, seeds have developed over millions of years with defenses to survive awful conditions. But, in your modern day garden, a seed is relatively pampered. Soaking seeds before planting helps you to break down the seed’s natural defenses against what it expects from Mother Nature, which then allows it to germinate faster.

While Mother Nature actively assaults seeds, she also gave those seeds an internal gauge to help them know when they should grow. For most seeds, moisture levels play a big role in alerting a seed to optimal grow times. By soaking the seeds, you can quickly boost the moisture content around the seeds, which signals to the seed that it is now safe to grow.

Lastly, some types of seeds actually contain germination inhibitors that are designed to prevent a seed from germinating inside the fruit. These inhibitors must be leached away before a seed can germinate. In nature, relying on natural rainfall, this process can take some time. Soaking seeds can speed this process up.

Soaking green pea seeds with warm water in bowl to quicken the germination process. Source: FotoHelin/Shutterstock

How to Soak Seeds Before Planting

Seed soaking at a basic level needs two things: seeds and water. Some methods for seed soaking may substitute the water for slightly acidic solutions, such as weak tea or coffee or even acidic chemicals. These acidic solutions are meant to imitate loosely the stomach acid of an animal, but these solutions are not necessary in most cases. For most seeds, water will work just fine.

Take a small bowl and fill it with water from your tap, as hot as your tap will allow. Some seeds can tolerate boiling water, but as the tolerance for heat can vary greatly from species to species, hot tap water is safest for seed soaking.

Once your bowl is filled with hot water, place your seeds inside and allow the seeds to stay in the water as it cools down. Common questions at this point include, “How long should seeds be soaked?” and, “Can you over-soak seeds?”

Yes, you can over-soak seeds. Too much soaking in water and a seed will drown. It is recommended that you only soak most seeds for 12 to 24 hours and no more than 48 hours. The seeds of some species of plants can survive longer soakings, but you should only do this if the specific instructions for this species recommend so.

There are things you can do to improve how well your seeds react to soaking. Large seeds or seeds with particularly hard coats can benefit from scarification before soaking.

Scarification means to damage the seed coat in some way so that the water is better able to penetrate the seed. Scarification can be done in several ways, including rubbing the seed on fine grain sand paper, nicking the seed coat with a knife and even gently tapping the seed with a hammer to help crack the seed coat.

After soaking your seeds, they can be planted as directed. The benefit of soaking seeds before planting is that your germination time will be reduced, which means you can have happily-growing plants faster.

How to Germinate Marijuana Seeds

Germinating marijuana seeds and caring for marijuana seedlings is one of the easiest steps in growing marijuana. That said, if you do not know what you are doing, it is also an easy step to get wrong. High quality marijuana seeds are not cheap, and ordering them can be risky. So you want your germination rates as high as possible. Here are some of the surefire ways marijuana growers limit environmental stresses and help marijuana seeds grow into healthy, vigorous and hopefully female marijuana plants.

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Selecting Marijuana Seeds

Entire books have been written on choosing the type of marijuana strain to grow, but here are some general guidelines for determining the viability of a marijuana seed.

It is not always easy to tell if a marijuana seed will germinate simply by looking at it, but it is not hard to weed out the weak ones. Healthy, viable marijuana seeds should be slightly oblong and shaped like a teardrop with a point at one end. Size varies ,but marijuana seeds are usually about 1/8th of an inch wide and 3/16th of an inch long. Their color is usually brown, often with darker stripes like a brindle dog. Â Marijuana seeds that are tiny, soft (immature), greenish, yellow, white, or chipped are not likely to germinate. In the end, there is really only one way to find out: try it and see.

Marijuana Seed Germination

Germinating marijuana seeds requires only the correct amount of water, heat, and air. Nothing more is needed; nor is it even beneficial.

Water – Marijuana seeds require moisture to trigger the hormonal changes that make the germination process possible. Planting your seeds in high quality soil or pH balanced Rockwool and watering regularly to maintain constant moisture will be sufficient for most marijuana seeds to germinate. As water passes through the seed’s shell, dormant hormones stored within the seed are activated. As the water continues to penetrate the shell, the seed will begin to grow and produce a taproot. Constant available moisture is required to continue the seed’s growth into a healthy plant.

Ideally, you should use bottled drinking water for germination. Tap water from a municipal water supply usually works fine, but contains chlorine. Well water can contain high levels of dissolved solids that can hamper early root growth. The chlorine in municipal water is not a major problem, and will dissipate if left exposed to the air.

Here is some further information to answer any questions about water quality and growing marijuana.

Heat – Marijuana seeds can germinate in many temperature conditions, but grow best between 75 and 80 degrees Fahrenheit (23-26 C). Cooler temperatures slow seed germination and promote fungal growth such as fusarium and pythium which can rot the seed and root. Temperatures above 90 degrees can also inhibit germination.

Oxygen – Marijuana seeds require air–specifically oxygen–to germinate. After germination the roots will require air, and the leaves will require CO2. Marijuana is native to primarily arid climates, not jungles and swamps. So if the growing medium is too moist or the seed is soaked for too long, the seed will not receive enough oxygen and will drown. Covering the growing medium with plastic wrap or a seedling dome will trap moisture and limit air exchange; so do not use them. Humidity above 50% promotes the growth of fungus that can damage and kill a marijuana plant while germinating or sprouting.

To promote the highest rates of germination and optimal health you want a warm, moist but not soggy growing medium, and warm circulating air that is under 50% humidity.

Steps 1 – 4 are Entirely Optional

You can use all of these steps, some of them, or none of them at all. Older seeds or seeds that have been allowed to dry out a bit too much are likely to benefit from steps 1 to 4. Marijuana seeds stored correctly that are less than three years old should germinate just fine without these extra steps. Â Using these extra steps on newer seeds generally does not create problems and can increase your germination rates, though some advise against them as they increase the potential for human error. Â If you skip earlier steps and your seeds do not germinate, you can always go back to earlier steps and try again.

Step 1: Scuffing Marijuana Seeds

By lightly scuffing marijuana seeds with sand, sandpaper, or an emery board you can create tiny scratches in the hull of the seed making it easier for water to penetrate the hull and reach the embryo inside.

Step 2: Soaking Marijuana Seeds

Soaking marijuana seeds in a glass of water can speed up the germination process. Simply place your marijuana seeds in a glass of room temperature bottled drinking water. If the seeds float you can dunk them under a few times with your finger. The seeds should be soaked for 2 to 24 hours, but certainly no longer.

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Step 3: Paper Towel Germination

Place a paper towel on a flat but mobile surface like a dinner plate and then place your marijuana seeds on the paper towel. Cover the seeds with a second paper towel and pour bottled water over the top, until the entire paper towel is soaked with water. Tilt the plate to an angle of about 45 degrees so that any extra water will run down and drip off the plate. Place the plate on a heating mat if possible and set the thermostat to 75 F (24 C). Insert the thermostat probe under the paper towels.

As soon as the marijuana seed’s shell has opened and the tap root has begun to show, the seed needs to be planted immediately. This may mean that not all of your seeds get planted at the same time. Do not let the root grow to be several millimeters long before planting, or you drastically increase the likelihood of damaging the root and killing the plant.

Note: In nature, seeds germinate under soil where it is dark; so you do not need lights for germinating. Light can be used to heat a small area if you do not have a heat mat. Take care to  monitor the germination process closely, however, as the light will dry out the paper towels more quickly and damage the root once the seeds open. Also remember heating mats can overheat, and either boil your poor little seeds or cause the paper towels to dry out more quickly. So be sure you use a thermostat for your heating mat.

Step 4: Planting Your Marijuana Seeds

Soil – Fill your small pots with a light and airy potting soil. Gently press the soil down to compact it slightly. Drench the soil with clean water, making sure that all of the soil is uniformly damp but not soggy or waterlogged. Make sure to test the pH of your water and balance it to 6.3 if needed. Create a hole in the soil about half an inch deep with the end of your finger. Gently pick up the marijuana seed with a pair of tweezers and place it taproot (pointed end) down at the bottom of the hole. Gently fill the hole with loose soil to cover the marijuana seed. If you are not sure about what kinds of soil use, here are some helpful directions on the best soil for germinating marijuana seeds.

Note – If you use pots that are too large you will be taking up unnecessary space which will make it more difficult to fit your pots on a heating pad. You will also be bringing a lot more moisture into the room, which means you are wasting money on nutrients each time you water. Also, remember that as this extra water evaporates it will drive up the ambient humidity of the room, increasing the potential for humidity-related problems such as bugs, mildew and mold.

Rockwool – Because Rockwool cubes start with a high pH, you need to adjust the pH down by soaking the Rockwool in lukewarm water with a pH of 5.5.  Let the Rockwool soak for about half an hour and then remove it from the water, letting the extra water drain off.  Next flush the Rockwool with fresh pH 5.5 water, not the water they already soaked in.  After the Rockwool is flushed, create a small hole about half an inch deep with a pencil or screwdriver. Gently pick up the marijuana seed with tweezers and place the seed –tap root (pointed end) down–in the hole. Cover the seed with some loose Rockwool that has also been pH-balanced.

Note – Be sure not to pack the Rockwool around the seed, as it will need to move past or through it. Do not squeeze extra water from the Rockwool, as this can compress it and change the intended air-to-moisture ratio that Rockwool is designed to optimize. Also, remember when growing marijuana in Rockwool it is important to monitor not only the pH of the water you are supplying to the seeds/plants, but also the pH of the runoff water. To keep the Rockwool cubes from sitting in a pool of runoff water, try setting them on a thin layer of perlite.

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Step 5: Watering In and Situating Stuff

If you properly drenched the soil or Rockwool before planting, watering in is pretty easy. Just take a few spoonfuls of pH-adjusted water and re-soak the area containing the marijuana seed. This may not be necessary, but will ensure moisture to that area. It is of utmost importance to keep the soil or Rockwool as evenly moist as possible, as dry areas will wick moisture away from the seed. If you allow your growing medium to dry out, it will likely be fatal for your seedlings. Be careful to water very gently. Otherwise, the flow of water can easily uproot a seed before the roots have taken hold. Misting bottles don’t penetrate deeply enough into the soil, so continue to water wit the spoon until the seedling is well-established.

Place the pots or Rockwool cubes in seedling trays, and place the tray on a heat mat with the thermostat set to 75 degrees F (24 C), and the sensor probe either in the soil or the Rockwool. The marijuana seedlings are going to need light as soon as they emerge.  So you might as well turn the lights on from the start. This will give you a few days to observe the effects of the lights on temperature and humidity in the room, and make any needed adjustments. There is no need to throw huge amounts of light at tiny marijuana seedlings. I recommend T5 florescent grow lights with both Blue and Red color spectrum bulbs. T5’s are easy to set up and take down, and much less expensive to buy and operate than the HID grow lights that you will use to grow more mature marijuana plants. They also produce less heat. Make sure the ambient temperature of the room stays in the mid to high 70’s both day and night. Maintain the grow rooms humidity between between 20% and 40% if possible, and certainly no higher then 55%.

Step 6: Caring For Marijuana Seedlings

Within two-five days the seedlings should emerge from the growing medium and, shedding their shells, reveal their ovular embryo leaves (cotyledons). Occasionally, the cotyledons are not strong enough to shed the shell, and may need some very gentle assistance. Try to avoid this if possible, as it requires a jeweler’s precision and can easily go wrong. If you are using T5 Fluorescent Grow Lights, they should be between six and eight inches from the tops of the marijuana seedlings. Set the timer for 18 hours on and six hours off.

For Soil – Once the seedlings have emerged, I recommend waiting a week before adding a 20% strength nutrient to the water.

For Rockwool – You can begin feeding with diluted (20% maximum strength) nutrients as soon as you like. Remember the marijuana seedlings are very fragile at this point. Even a slight miscalculation in nutrient strength can easily kill the seedlings. If you like, you may wait up to a week to begin feeding.

What Not To Do

  • Do not use humidity domes or anything else to cover the pots
  • Do not use heating mats without a thermostat (80 degrees max)
  • Do not use jiffy or peat pellets because the create pH problems
  • Do not use soil that is high in N-P-K, “Hot” or otherwise unsuitable for seedlings
  • Do not fertilize your seedlings in soil for the first week, or use more than 20% strength for seedlings in Rockwool
  • Do not water-log your seeds or seedlings, or allow them to dry out
  • Do not germinate seeds where they will get too cold
  • Do not deprive seedlings of adequate light
  • Do not use water with incorrect pH or other problems
  • Do not foliar feed or spray anything, including water and pesticides, on seedlings
  • Do not handle seeds with bare hands if possible. The oil from your hands can prevent water from soaking in.

Well, this should keep you busy for a week or so. In the meantime, I will be preparing some basic directions to help get you and your marijuana plants through the vegetative period.