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germinating cannabis seeds in a propagator

Offer enough Light for Cannabis Seeds

Apr 16, 2019 · 6 min read

Cannabis seeds don’t need light when they are germinating. In fact, they require an absence of light. All of the methods below call for darkness.

Once they have sprouted, they will need a lot of light — 18 hours a day, to be exact (though you could even give them 24 hours of light per day).

How To Germinate Cannabis Seeds

There are several methods for germinati n g marijuana seeds, each with their pros and cons. We will cover the best methods below, with the first method offering the best chance of success and the last one offering the lowest chance.

These seeds are expensive, so we recommend using the method with the best chance of success, so you reduce the risk of wasting seeds as much as you possibly can.

Germinating Cannabis Seeds In A Propagator With Peat Pellets
You get the highest success rate when you provide the perfect environment for germination. A propagator ensures optimal control over the environment.

Whether using peat pellets or rapid rooters, this method ensures a high rate of success, but it does require the purchase of a propagator and the pellets or rapid rooters.

You can save a bit of money by skipping the propagator and just rigging something up yourself (or not using any type of covering at all), which is what we’ll cover next.

Using Peat Pellets With No Propagator (Or With A DIY Propagator)
If you are on a bit of a budget, you can forgo the propagator and just use peat pellets on their own. You could even make a DIY propagator by simply using some kind of plastic cover.

Pros
lower cost than using propagator
peat pellets (or rapid rooters) still offer the best chance of success, even without a propagator
Cons
less control than with propagator
if using a DIY propagator, requires time to construct

A great DIY solution is to use simple plastic cups, one for each peat pellet. Cut the top off a small plastic drink bottle and place it over the peat pellet with the seed as a dome.

But you don’t need any propagator at all.

Covering the seeds helps keep in the moisture and makes it easier to keep them warm, but it is not necessary. You can just as easily keep the peat pellets uncovered, as long as you ensure they stay moist and are kept in the correct temperature range.

Germinating Cannabis Seeds Using Paper Towels
This is probably the most written about method, but that does not make it the best. It is easy and you won’t need any additional equipment, but it requires handling the delicate seedling.

Pros
very easy
no additional equipment required (assuming you have paper towels)
Cons
requires transplanting the seeds, which risks damage
need to ensure the paper towel stays damp, but not wet

The only thing you need for this method is a paper towel, although I would also recommend using two plates.

For the paper towel, you actually want to use the cheapest brands. More expensive towels are more porous, which makes it easier for the delicate root to get stuck and tear off when transplanting the seedling.

For this method, place a paper towel on a plate and get it nice and wet. Drain off any excess water, though. It should be damp, but there should be no standing water or the seeds can drown.

Put your seeds on one half of the paper towel and fold the other half over them, so that they are covered. Then take the second plate and put it upside down on the bottom one, forming a dark cavern between the two plates for the seed to germinate.

Check once or twice a day to ensure that the paper towel never dries out. If you need to add water, make sure that you always drain out any standing water. Keep the seeds covered and at the correct temperature. They should sprout in a few days.

Once they have sprouted, you’ll want to transfer them to soil or a growing medium. See below for instructions on how to do this.

Germinating Weed Seeds In Soil
This method is the easiest, since you simply let the seeds germinate in the same place where they will grow afterward. Not having to transplant the seed after it sprouts means you don’t risk damaging it causing it shock that will slow growth. The main drawback is a lower success rate.

Pros
easiest method
no transplanting required
no additional equipment required
Cons
lower success rate than other methods

All you do for this method is poke a hole in the soil or growing medium that is about half an inch deep (1.5 cm). Place the seed in the hole and cover it up. Ensure that the soil or growing medium is moist, but not soaking wet. The temperature needs to be in the correct range as well.

You should see the tap root poking out of the seeds by then. If not, you’ll want to continue germinating the seeds elsewhere, perhaps in soil. If they are submerged in water for more than 24 hours, there is a risk that the seeds can drown.

My Seeds Germinated, Now What?
Once the seeds have germinated, it is time to transplant them into soil or a growing medium. Be very careful not to damage the delicate taproot. Ideally, use tweezers to handle the seeds, to avoid any oils from your fingers doing any damage.

Plant the seeds about 1 to 2 cm deep, so that it does not require too much energy for the stem and first leaves to pop up through the soil.

Make sure the soil is moist and the seeds are kept at the correct temperature of 68° to 82° F (20° to 28° C). Your little plants should pop out of the soil within a few days.

At this point, the seeds will want light, and lots of it. Even if they are still beneath the soil, you can go ahead and turn on your grow light.

If you do not have a grow light, there are a number of different types you can consider. For seedlings, fluorescent lights or LED light bars (like the veg/clone bars from Secret Jardin) are ideal, unless you are germinating a lot of seeds at once. Then you might want to consider a larger Plant LED grow light.

Best LED Grow Lights For Starting Seeds
The best LED grow light for seedlings is the AIS led GROW LIGHT. It was specially designed for seedlings. The main drawback is that it is made to cover a 2 by 4 foot area. If you only have a few seedlings, this light will be overkill.

LED bars are the best LED lights for seed starting when you don’t have enough seedlings to fill a 2 by 4 foot area. These bars from Secret Jardin are a great choice. They are inexpensive and give off enough light to get your plants through the seedling stage in no time.

HPS Or MH For Seedlings
You can put seedlings under HPS or MH light, but I would only suggest this if you already have the lights. It is more cost effective to use LED or fluorescent lights.

The only time MH or HPS really makes sense is if you keep your plants in the same space from seed to harvest, i.e. you do not have a separate area for seedlings.

Metal halide light is better for seedlings than HPS light, since they need cooler light with more blue light than red.

When To Put Seedlings Under MH or HPS
You can turn the grow light on once the seeds have sprouted and they are in the soil or growing medium. Even if the plant is still not visible, the heat from the grow light will actually help warm the soil, which encourages the plant to grow.

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Cannabis seeds don’t need light when they are germinating. In fact, they require an absence of light. All of the methods below call for darkness. Once they have sprouted, they will need a lot of…

What are the best conditions for seedlings?

Read this article to learn about the best conditions for your cannabis seedlings. Learn about optimum temperatures, light exposure, air conditions, and the equipment you’ll need to get the best possible results.

The best conditions for cannabis seedlings are a bright, warm (21-23ºC) and humid environment with moving air.

Propagators are simple to obtain and provide an ideal start for young cannabis plants. A propagator is a plastic tray with a transparent top which holds in humidity and warm air while allowing seedlings to receive light. This an easy way to maintain a good environment for very young seedlings . However, since the cover prevents normal air movement (which is very important as it encourages young plants to grow strong stems), cannabis seedlings should not be kept in a covered propagator for too long.

Once the young plants produce their second or third pair of serrated leaves, or if they grow taller than about 7 cm with only the first pair, the cover of the propagator should be removed. A small oscillating fan on the lowest setting is a good way to give indoor plants the air movement they need, while outdoor plants can start to receive the natural outdoor air movement when they have reached this size.

After seeds are sown in the growing medium, they can be placed in a propagator for the first couple of weeks.

The simplest form of propagator would be a waterproof box with clear plastic sheeting over the top. The advantage of shop-bought propagators is that they often have built-in heating and/or vents in the cover to allow temperature and humidity regulation. They also usually allow more light to reach the seedlings.

If the seedlings are intended for outdoor growing, the covered propagator should be placed next to a window to give the seedlings light. By the time outdoor seedlings are big enough to have the propagator’s cover removed, the process of acclimatizing them to outdoor conditions can begin (weather allowing).

The seeds have germinated but what are the best conditions for seedlings? Find out here.