Cactus Seed Germination 101 – The Definitive Guide

This article is heavily based on the tried and tested Takeaway Tek. 

A lot of my process is the same as the default Takeaway Tek with a few modifcations that have suited us and our style of doing things. 

A special thanks to those who have helped me through the years, the community and knowledge sharing is the best I have come across. Sir Richard B, Kevin M & Kristian D specifically, thanks brothers.

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Some of the links provided in this article use affiliate links to Amazon. If you go to Amazon and purchase the product, we will receive a small comission for the referral. This in no way affects the price you pay. All the products I recommend are products that I use personally.

Introduction 

The Takeaway Tek has become the gold standard of seed germination, mainly due to ease of application and the low cost of implementing. In it’s simplest form, you need a tub, soil & light.

I will try and outline the full process in as much detail as I can. There will also be sections where I give pivot options and additional tips that has served us well over the years.

For us as a business, our goal is to get germinated seeds to a sellable size within 12 months. To do this, we have to be aggressive on fertilisation and selective when transplanting (only the strong will survive).

We try and achieve the following:

1. Start acclimating seedlings to open air at week 12
2. Repot seedlings into individual pots at the 6 month mark and into indirect light.

So, please take anything described in the article as a possible guide to chunky seedlings within a year.

Nothing stated in the article is set in stone and I invite you to try different things and go with what works for you, personally.

This is long overdue, let’s get cracking :-).

Summary of Process

1. Preparing the Soil

• Mix the soil components thoroughly.
• Optionally, sterilize the soil by:
  • Baking it at 80-100°C for 30 minutes, OR
  • Microwaving it in a heatproof container for 2-3 minutes.
• Let the soil cool before proceeding.

2. Preparing the Container

• Clean the container with warm water and soap.
• Optionally, wipe the inside with a diluted hydrogen peroxide solution to prevent mold.
• Optionally, use 70% ISO Propyl Alcohol (Rubbing Alcohol) and wipe all inner surfaces.

3. Sowing the Seeds

• Fill the container with about 2-3 cm of the prepared soil.
• Lightly mist the soil with water until evenly moist (not soaking wet).
• Evenly distribute the seeds on the surface—do not bury them.
• Lightly mist the seeds again to help them settle.

4. Creating the Germination Chamber

• Close the lid securely to maintain humidity.
• Place the container in indirect light—a bright windowsill or under grow lights is ideal.
• Maintain a temperature of 20-28°C for optimal germination.
• If using a heat mat, set it to 20°C to stop the temps dropping below that.

5. Monitoring Germination

• Germination typically begins within 5-14 days, but some seeds may take longer.
• Keep the lid closed for the first 12 weeks to maintain high humidity.
• If condensation becomes excessive, briefly open the lid for air exchange.

6. Post-Germination Care (Hardening Off)

• After 12 weeks, start introducing fresh air by slowly opening up the tub to more fresh air.
• Gradually increase air exposure over the next few weeks.
• Once seedlings have a few spines and are stable, they can be transplanted into individual pots.

Step-by-Step Guide

Make sure you have all materials at hand when starting, this probably does not need to be mentioned but it’s mainly for all you ADHD folk who get excited and just headbutt in 🙂

Materials Needed

1. Takeaway Container or Propagation Dome
   • The container should be transparent to allow light to reach the seeds.
   • The container must be air tight to lock in the humidity and moisture.
     • You can use the Takeaway tub lid (recommended for ease of use), or
     • Use clingfilm to wrap the tub and lock in the environment
     • If using a propagation dome, you will have some moisture leakage due to the fact that the lid is not airtight.
2. Substrate
   • 60% organic (compost, worm castings etc)
   • 40% grit (small form grit is recommended, 1mm to 3mm)
3. Cactus Seeds
   • Fresh, viable seeds increase germination success.
   • Please see our seed list for options.
4. Distilled, Spring or Rainwater
   • Avoid tap water or dechloronate if you have no other options.
   • If using tap water, we do offer Ecothrive Neutralise which dechlorinates.
5. Hydrogen Peroxide (Optional but HIGHLY recommended)
   • 3% H2O2 can be used for sterilizing the soil and preventing mold growth.
6. Spray Bottle
   • For moistening the soil.
7. Artificial Lighting (Optional but highly recommended)
   • A cheap LED grow light will be more than enough
   • Our Ogema Clone LEDs work well for seed germination.
8. Heat Mat (Optional)
   • Helps maintain optimal temperature min temp of 20c.
   • We do offer heat mats of various sizes.
9. Fungicide (Optional)
   • Any UK fungicide should work. Resolva Rose Clear Ultra will do the trick.

Preparing the Substrate

For seed germination, we do not require large form grit. That is not to say it will not work, it will. In my experience, micro grit just works well and there is little to no risk of over powering the germinated seeds.

Organics

For the organic side of the substrate, we use 50% sieved John Innes No2 (original JI receipe with peat), 50% worm castings. We also add mycorrhizae to get the soil microbes firing and giving the babies the best possible start.

Inorganics

We use lint chicken flint grit (1mm to 3mm) but, any small form grit will be absolutely fine (even disgusting perlite). There is an argument for potentially using biochar, but, its takes a long time to get fully innoculated for use.

Grit Options

• Chicket flint grit (1mm to 3mm) – Recommended
• Horicultural Grit (bit big for seeds in my opinion although I have successfully used it in the past).
• Pumice – Great for adding aeration.
• Molar Clay – As above.
• Vermiculite – Can be used as a moisture retaining top layer.

It really comes down to what you have access to and your budget. We use the flint chicken grit only as the inorganic component.

Once you have your components, all you need to do is mix it up in the required ratios and hydrate.

Hydrating the Substrate

Add small amounts of spring / distilled or rainwater to the substrate mix till it is at “field capacity”. Basically, you want the substrate to be moist but not wet.

A good way to see if the moisture content is within range is to take a clump of substrate in your hand and squeeze. Ideally, only a couple drops should squeeze out. If you get a steady stream of water, you have over done the moisture and need to add more substrate to correct.

As per Herbalistics, for a 600ml takeaway tub, adding around 25ml to 50ml of water is a good starting point. Personally, I have never measured. I just add some water, squeeze and go from there (mainly because we do big batches).

To end out this section, having too much moisture can make life difficult:

• It can affect germination rates.
• Can cuase the new and very fragile roots to rot.
• Moss and fungal build up will become a problem.

That being said, I have overdone the moisture content a lot of times and have been alright. You just have to monitor and be ready with the H2O2 just in case.

To STERILISE or Not?

A lot of growers recommend sterilising the substrate either by microwaving for 2 to 3 minutes, using a Pressure Cooker or pasturising. 

The biggest problem I have with sterilisation is the fact that everything does, good and bad. In my opinion, having beneficial microbes present from the outset far outweighs any baddys that might be present. 

Our official recommendation is to bin the idea of sterilisation and just crack on, you will be fine :-).

Container Preparation

This section will outline two different approaches achieving the same net result, a contained and humid environment for seeds to flourish. This is also not the only two ways to germinate, its just the best two options in my opinion.

Takeaway Tub

Any transparent tub will do, really. The only requirement is to be able to seal it up and lock in moisture and humidity. 

You can either use the takeaway tub lid to seal up after sewing or you can use clingfilm to wrap it up completely.

I would recommend this route for anyone starting out or is germinating less than 100 seeds. 

Propagation Dome

A propagation dome potentially has a small benefit over takeaway tubs. The main one being the fact that the dome lid will allow for more air to be contained within the environment. Personally, I have not noticed this to make much of a difference.

More monitoring will be required with a propagation / humidty dome as the seal to the tray will not be airtight, rehydration may potentially be required if too much moisture escapes.

If using a prop dome, I recommend using tubs in the tray as its easier to manage and spreads risk. if one tub goes south, not everything is lost.

Some Notes: 

• Regardless of whichever container type you choose, the substrate should have a depth of at least 2 to 3cm. The deeper the better but be mindful of the vertical space to grow if using takeaway tubs.
• Try and get the top surface of the substrate as flat as possible. I use a kitchen spatula to flatten the top.
• It is recommended to ‘sterilise’ the container with something like 70% ISO Propyl Alcohol. Personally, I do not do this anymore as I do not sterilise the substrate.

Seed PREP & Germination

Seed preparation

Before I germinate any seeds, I always pre-soak the seeds in 3% H2O2 for anywhere between 4 hours and 24 hours depending on my time contraints and patience. Pre-soaking the seeds will mainly kill off any spores present on the seed shell, but it will also soften the outer shell, which can increase germination rates. Although this is optional, it is highly recommended as it drastically decreases the chance of nastys ruining the party.

Germination Prep

Now that we have our environment ready and prepared, it is time to get the seeds into the chosen container.

The most optimal way would be to individually place each seed uniformly in the tubs using something like plastic tweezers. This is ok if you are working with a small amount of seed. But, if you are like me, this is not the case and I tend to sprinkle the seeds in trying my best to create an even spread. This can create clumped seedlings but thats a problem for down the line.

Once all of the seeds are on the substrate (do not bury them), you can then give a few sprays of H202 to hydrate the top layer and kill off any spores present on the seeds. Another option would be to use a fungicide spray, something like Resolva Roseclear Ultra. The active ingredients will stay active for a couple weeks and will reduce the risk of fungals by a lot.

I give a couple sprays of 3% H202 and the fungicide for added protection.

Wrapping Up

To finish up this part of the process, all you need to do now is close everything up. This can be achieved by closing the lid or wrapping the container with clingfilm. 

Environment Preparation

Temp Ranges

The optimal temp ranges for the seeds is 20c to 28c. We recommend having a heat mat that is set to 20c, this ensures that the temps do not fall below the min range and keeps the seeds in optimal range.

Given that most germination happens indoors, the heat mat is more a fail safe than anything else as indoor temps are normally stable year round.

Lastly, hotter does not mean better. Algae and moss thrive in high heat / high humidity environments. To minimise spread, the lower side of the temp range is recommended.

Lighting Requirements

If you are germinating in early Spring, artificial lighting is not a requirement but I still do recommend using one. Using artificial lighting allows you to control the environment variables and can easily adapt if the situation calls for it.

LED has become the standard for growing these days due to it’s efficiency and longevity. Something like our Omega Clone LED Lights will do the trick up to around the 6 month mark. Alternatively, any cheap LED grow light off Ebay or Amazon will work.

Environment Final Note

Using both a heat mat and LED lights allow you to control pretty much everything in the process. You can easily increase / decrease light exposure by lifting / lowering the LED lights and you can maintain optimal temps by never letting the seeds drop below 20c.

Maintenance

The seed germination times vary greatly depending on how old the seeds are. The fresher the seeds, the higher the germination rates will naturally be. That being said, there are ways to bump old seed germination rates, but that is out of scope of this article.

Seeds should start popping within 5 to 14 days, happy days. This is always the worst part for me, waiting :-).

Once the seeds start popping, you need to keep an eye on the colour of the seedlings as that will tell you how they are doing and if any corrective measures are required.

Colours and Causes

As a rule, the following applies to seedling colours:

• Red – Too much light exposure
  • Option 1: You can raise the lighting or move the tubs into more indirect light if using natural light.
  • Option 2: Cover the container to block some light. I split kitchen roll and put each half of the square on top of the lid which filters light hitting the seedlings.
• Yellow – Not enough light exposure
  • If using LEDs, lower the lights to get closer to the seedlings and monitor.
  • If using natural light, a more exposed area is needed.
• Green – Well done, you are winning cactus 🙂

Timeline

The most ideal scenario would allow for you to keep everything closed up for a minimum of 12 weeks, I find this to be the sweet spot. But, as long as the seedlings have spines, they can be hardened off (acclimated).

Scenarios where opening up early would be in the event of fungal spread or algae / moss starving the seedling’s roots. In this case, you would start hardening off earlier than intended to protect the seedlings.

Acclimation / Hardening Off

When ready, the seedlings will need to be slowly introduced to open air and the drop in humidity. Please take your time here because if you open up too quickly, it will shock the seedlings and stunt / delay grow for a while. Ideally, you want the hardening off process to take at least 2 weeks to fully prepare the seedlings for open air.

To harden off the seedlings:

• Takeaway Tub
  • If using lid, pop the lid and then increase the openings a little every few days.
  • Clingfilm, this is where clingfilm can be advantageous as you can poke holes with a toothpick every few days.
• Propagation Dome
  • The lids normally come with vents which you can slowly open.
  • Once vents are fully open, you will need to take the lids off for a while each day to allow for fresh air exchange and more hardening off. You can also dialodge the lid to create air gaps.

Once the seedlings are fully acclimated, I start to lightly fertilise using quarter strength seaweed feed.

Repotting

At the 6 month mark, I repot everything into individual pots and then into indirect light to get used to the outdoor environment. There may be some losses here but that should be expected, the trick is to repot the seedlings while trying not to disturb the root mass as much as possible. This will greatly reduce any casualties.

Troubleshooting COmmon Challenges

The biggest challenges you will face is mold, algae and moss. The former is the biggest concern because if mould sets in, it can destroy the whole tub in days. 

Mold & Fungus Growth

Symptoms:

• White, green, or black fuzzy growth on soil or seedlings.
• Seeds appear to rot instead of germinating.

Causes:

• Too much moisture.
• Contaminated soil or seeds.

Solutions:

• Prevention:
  • Use a suitable fungicide and periodically give the surface of the tubs a couple of sprays.
• Treatment:
  • Spray with a fungicide.
  • Lightly spray infected areas with 3% hydrogen peroxide. Although the seedlings can handle 3% H2O2, it is best to try and avoid the seedlings when applying H2O2. I have had scenarios where it’s been too strong and has bleached the seedlings (I was stupidly using a higher strength).
  • Increase ventilation by temporarily opening the environment to allow for fresh air exchange.
  • If mold spreads aggressively, remove affected seedlings.

Seeds Not Germinating

Symptoms:

• No visible sprouts after 2-4 weeks.

Causes:

• Old or low-quality seeds.
• Incorrect temperature (too cold or too hot).
• Soil dried out or was too wet.

Solutions:

• Use fresh, high-quality seeds. Trichocereus seeds typically remain viable for 1-2 years but lose viability after that.
• Maintain proper temperature (20-28°C). Use a heat mat if necessary.
• Keep soil evenly moist, not soaked. If it dries out, mist lightly to rehydrate.

Pro Tip: As mentioned earlier, to increase seed viablility and kill off any spores that may be present on the seeds (this is where most spores originate from), you can soak the seeds in 3% H2O2 for anywhere from 4 hours to 48 hours. I generally soak for between 4 and 24 hours before germinating.

Seedlings Growing Tall & Thin (Etiolation)

Symptoms:

• Seedlings become stretched, pale, and weak.

Causes:

• Insufficient light.

Solutions:

• Move the container to a brighter location. Indirect sunlight or grow lights are best.
• Use artificial lighting (LED or fluorescent grow lights) for at least 12-16 hours per day and get the light source closer to the plants.
• Gradually transition seedlings to stronger light once they have spines.

Rotting Seedlings (“Damping Off”)

Symptoms:

• Seedlings collapse and turn brown or mushy.

Causes:

• Too much moisture.
• Fungal or bacterial infections.

Solutions:

• Reduce moisture: Open the container gradually to improve airflow.
• Improve drainage: If the soil stays too wet, mix in more perlite or sand.
• Spray seedlings with diluted (3% H2O2) hydrogen peroxide to prevent further infection.

Germination variations

1. “Bag Tek” (Ziplock Germination Method)

Instead of a plastic container, you can use ziplock bags:

• Place moistened soil and seeds in a small plastic bag.
• Seal the bag and place it under indirect light.
• Open briefly for airflow after 3-4 weeks.

Pros: More compact, great for large seed batches.
Cons: Less control over airflow, harder to monitor seedlings.

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2. “Perlite Dome Method”

• Instead of soil, place pure perlite (yuk, I would recommend perlite or molar) as a base layer inside the container.
• Set a small pot with the seed mix on top.
• The perlite maintains humidity without soaking the soil.

Pros: Reduces mold risk, maintains moisture evenly.
Cons: Requires an additional step of transplanting once seedlings grow.

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3. “Bottom-Watering Takeaway Tek”

• Instead of misting, water the bottom of the container lightly (the tubs will need to have holes created).
• The soil absorbs water from below, reducing the risk of overwatering.

Pros: Less risk of fungus, more stable moisture levels.
Cons: Requires careful monitoring to prevent excess moisture.

CONCLUSION

This article has grown legs and I hope it provides some valuable insight into the seed germination process without confusing the hell out of you.

If you have any questions or need anything clarified, feel free to leave a comment and I will do my best to address.