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The Seedsman Grow Guide – Germination

Before you start to germinate your seeds you will need to prepare an ideal space for them to exist happily until they are ready to be potted up and grown on. So many people start seeds without any thought as to what they will do with them once they germinate.

Or, if you are only starting a few seeds, to plant outside, you will only need a few small pots and a small fluorescent light bulb above the seedlings or even a window ledge if it is spring or summer, just until they are big enough to pot up or plant in he ground

If you are looking to produce a bumper indoor harvest it is advisable to have a space already prepared and tested for temperature range with your grow lights running for 18 hours.  If your extraction system is adequate you won’t experience any heat related issues.

Please refer to our ‘building a grow room guide’ for a detailed guide on how to choose an ideal space and prepare it for the plants. But at the very least, you should have a suitable light hanging in a wardrobe or custom grow box, which is extracted to remove excessive heat and supply constant fresh air. Ideally white or Mylar lined for maximum reflection.  Your light source should be between 5000 & 6500k  (white / blue) and be plugged into a suitable timer set for 18 hours of light per day, or a brightly lit window as long as you have more than 16 hours light per day.

Equipment List:

Here is a list of items you will need:

  • Shot glass of water for each strain
  • Small pots
  • Coir or soil or propagation cubes
  • Labels or plant tags
  • Waterproof marker pen
  • H2o2 (Hydrogen Peroxide)
  • Fluorescent/LED/HID Lighting
    (ideally 100w minimum for up to 20 seedlings.)

Regular or Feminized Seeds

It won’t make any difference to how you geminate the seeds if they are regular (male and female) or feminized seeds, but you will need to start extra seeds if using regular seeds because you cannot know how many male plants there will be. You don’t want male plants, so these will be composted.

As a general rule you can usually expect to get approximately 50% males, but it is entirely possible to get 1 or even 10 males from a packet of regular seeds. It is pure chance. Because of this I usually start 2.5 x the amount of seeds that I require. For instance, if I have space to grow out 9 plants I would start approx. 25 plants to ensure I have at least 9 good females, any extra females I can either discard or keep as mother plants for clones, something we will cover in more detail later on.

If your seeds are regular you don’t want to be wasting time, feed, grow medium and space growing males so it is best to pot up into smaller pots and either bloom them immediately from seed until they show sex and then put back under 24 hours of light to stop them flowering, so you can discard the males and only grow the females on, or alternatively, you can grow them until you can take some clones from each one and then root the clones under 12/12 light cycle so by the time they root they will be showing sex. This is the method I prefer. Once I know which are females, I discard the males and pot the females into 10L pots to be grown under 18/6 light cycle until they are big enough to bloom.

So, if your seeds are regular, just plan to grow out half of these, as you will very likely get 40-50% males.  It will simply mean that you will need to grow the 5 a little longer to fill your space before blooming them. Or to further simplify things, just buy feminized seeds so that you know all your plants should be females. It makes things much simpler.

Misting your seedlings with water and clonex rooting gel (5ml per Litre) will produce robust, seedlings with vigorous roots.

Step 1: Germinating Seeds

Personally, I prefer to pre-soak my seeds in tepid tap water with Hydrogen Peroxide at 1ml per litre.  This helps to keep everything sterile and adds oxygen to the water helping your seedlings to develop faster.  This is especially important if you are trying to germinate older seeds as old seeds usually contain mould spores, which could infect the seedling and kill it before it germinates. It is also wise to try to be sterile if you plan growing out your seedlings in a hydroponics system.

Simply fill a 1Ltr Jug with tap water, if it is winter and cold, mix with some hot till it’s just tepid; add 1ml of H202 and stir. 

TIP – If you are starting multiple strains at once I suggest simply adding water to the plastic zip bag that your seeds arrived in. This saves having lots of glasses and saves needing to label them until you pot them up.

Soak the seeds for 24 hours or until you see them split open which is usually just prior to the taproot emerging. Once you have soaked the seeds, prepare your pots of soil or coco coir or Rockwool cubes.

  • Because Rockwool has a natural pH of 9.0, Rockwool cubes must be soaked overnight in ph. 5.0. Water. Soaking for 24 hours in pH 5.0 water will reset the pH to approximately 6. Which is ideal for plants.  Do not squeeze Rockwool to drain excess water, simply allow to drain naturally.
  • If using coir, I recommend sterilizing it prior to use – you can soak it overnight in water with 3ml per Litre of H202. The next day simply drain the excess water before use.

Sea Of Green Tip!

The key to success when growing using the Sea of Green is to maintain an even as possible canopy so all your plants are receiving equal light levels and thus grow uniformly. To achieve this from seed is tricky as all seeds start at slightly different times resulting in quite a variance in the height of your seedlings.

I usually start my seeds on a plate on top of a layer wet tissue paper with another layer of wet tissue on top covered by another plate upside down to create a humid space for your seeds to germinate.

After a few days you can check to see how many have germinated and select the ones of equal length and plant them each in a pot exactly the same depth, increasing your chances of your seedlings growing at a more uniform rate.

Now you are ready to fill your pots with sterilized coir or soil and label each one with the strain name and number the pots so you can keep track of phenotypes later on.  It is advisable to line the bottom of your pots with an inch of clay balls (grow rocks) or gravel to aid aeration and to help your pots drain properly, then fill each pot to an inch below the top of the pot with coir or soil.

Poke a shallow hole (15mm) into the soil/coir and place a pre-soaked seed into each pot and cover lightly.  If you used the wet tissue method and have sprouted seedlings, simply poke a deeper hole to accommodate the taproot. Your grow medium temperature should be above 18oC. If the ambient temperature is lower than this, either place them in a warm wardrobe with vent holes and a small fan, ideal temperature for your room should be between 22 and 25oC.

If using presoaked Rockwool, place a seed into the hole.  Write the strain name and seed number onto a plastic plant label and stick one in each cube.  Water your seeds and leave in a well-lit location. Within 2 to 3 days we will have seedlings.

If we wish to grow outdoors, it’s simply a case of growing them on indoors until they are healthy young plants ready to transplant outside into your selected patch or greenhouse. 

TIP!  I get better results planting seeds into small pots and allowing the pots to get well rooted before I replant into a larger pot or straight into the ground. If we plant seeds in large pots they can struggle with the lack of oxygen and the soil will stay wet for a long time after watering’s as there aren’t any roots to take up the moisture and this can lead to the soil becoming slightly acidic which can stunt growth.

If we want to grow our seeds in a hydro system we simply transplant into a suitable container depending on type of system.

  • Pot of coir – wick, drip system or hand watering.
  • Pot of Rockwool plugs – wick system, drip system or Hand watering.
  • Mesh Basket of clay balls, hydroton. Flood and drain, dwc systems
  • Small mesh pot of clay balls – geoponics


The More light you can give your seedlings once germinated the faster they will grow and be better, stronger plants. Personally I prefer full spectrum LED (Light Emitting Diodes) such as LED units that use Samsung Lm301B or slightly cheaper Samsung Lm561c, these produce super bright, full spectrum lighting with UV and IR but with 60% less heat than other lights. But a cool white fluorescent will do just as well.

If using HID (High Intensity Discharge – such as Sodium, Halide or CMH (Ceramic Metal Halide) these produce a fair amount of heat and you should judge how close you can get it to your seedlings by wetting the back of your hand and hold under the light moving closer until you feel warmth from the lamp, that will be your ideal hanging height. Just keep your eye on the canopy heat levels as your seeds get taller and grow closer to the light.

Set your timer to 18 hours on and 6 off, your plants can be grown under 24 hours light but the dark period helps your plant produce more roots and roots equals uptake so the more roots, the more yield. 

If you are growing regular, non-feminized seeds, it is advisable to use the 18/6 lighting cycle because your plants will be huge monsters before they show sex if grown without any dark period.

Watering frequency

The most common mistake I see new growers make is overwatering their plants, especially seedlings which under low lighting and in a solo cup-sized pot will usually only need to be watered every 3 days until they have true leaves and are taking up more water then you can increase to every 2 days and so on.

I find watering seedlings is best done using a spray bottle, simply mist the surface of the soil/coir every morning until soaked. This adds lots of oxygen to the water and helps your seedlings develop faster and avoids overwatering.

If you are pushing them hard with high intensity lighting or very bright sunlight, you should check them regularly and judge the ideal frequency to water based on how fast they dry out. With each watering completely soak them allowing for 20% runoff. When you see roots bursting out the bottom of your first pot, you should repot within a week to avoid stress from being root bound.


If you are growing in an inert medium, such as Rockwool or coir, once you see the first serrated leaves you should feed daily with 1.0 EC grow nutrients ideally containing humic and or kelp.   Using a feed, feed, water regime will ensure you do not ever feed. If using soil, add some humic acid to your feeds water occasionally to increase nutrient uptake.

If you do not own an EC pen, just use 50% strength feeds, ph. To ph. 6.0 ideally with a PH. Pen but litmus type kits are available very cheaply from most garden centers and grow shops.

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