Pre- soaking Chilli seeds

Finding the best solution

It’s one thing to make comparisons; it’s another to ensure that the basis for comparison is correct. For example, I recently started a comparison exercise between various solutions for the pre-soaking of Chilli seeds before planting.  The experiment was to determine which of seaweed extract, saltpetre, or plain water with a few drops of detergent is the most effective in seed starting.

It was certainly easy enough to get the varieties part of the equation right. That just took choosing the types I wanted to grow and making sure the seeds for the experiment all came from the same packets. The water part was also easy. That was simply rainwater from my rain butt brought to lukewarm in the microwave. Similarly, the soaking period was also easy. I simply decided on the normal standard of an overnight period of between twelve and eighteen hours.

However, the difficulty came in trying to determine the dilutions I would use to make the comparisons more less on an equal footing. For example, were the solutions going to be strong or weak? To me, this will make a difference. Surely you would want to place the seeds on equal standing in terms of concentration of scarification agent. If you were, say, going to use a strong seaweed extract mix, you should also use a strong concentration of saltpetre etc. Surely a stronger concentration of one agent shouldn’t be compared with a weaker one of another. See where I am coming from? To figure out what to do, I decided to do some research. I definitely needed to get some clarity on this issue

As clear as mud!

It was all about as clear as mud when I tried to do research on this subject. If you search on the web for recommendations, you find many suggestions. None of these, however, have any correlation. With this in mind, I decided to try and put some logic into it to see whether I could make sense of it all

One recommendation for seaweed extract that I found is that you should use one part seaweed extract to four parts of water (e.g. one cup of extract to four cups of water). Another suggested using a concentration of eight percent (approx. one part extract to nine parts water). There were yet other concentrations, but this is where it was starting to become complicated.

It seems not all seaweed extracts are the same. They can be made with various varieties of seaweeds. Each type of seaweed extract needs to be dosed at a different concentration. What’s more, concentrations can vary for different seed varieties, i.e. what is good for a cucumber seed is not necessarily suitable for Chilli seeds. I was unable any information related to Chillies, so I finally decided to go with one part extract to four parts water.

Similarly, when I researched saltpetre, I found a recommendation to add a teaspoon of saltpetre to a quart of water. Yet others call for one per cent saltpetre to a litre of water (10 grams per litre). I also found one for ¼ teaspoon per pint of water. The recommendations were all over the place. However, it finally boiled down to about a teaspoon of saltpetre to a pint of water, and that’s what I decided to use. What I did vary , however  was the length of time the seeds should be soaked. This period ranged from four to seventy hours. However, the general principle is that the thinner a seed’s outer coat, the shorter the seed should be soaked for. I finally decided to go for overnight as a compromise

I am not sure where I found out about soaking seeds in water with a couple of drops of dish-washing liquid . I must have read it somewhere. However, I found it difficult to find any information on this. As I stated in my previous post, I can only believe that adding soap to a soaking steep would help wash away growth inhibitors and maybe pathogens. I can’t see it  helping soften the seeds coat. Perhaps I am wrong. Anyway, we will have to wait and see what happens on that front

Why is it necessary to soak seeds?

Birds digestive tract

In essence, the reason we soak seeds is that they can imbibe water. Simply put, this means the seed absorbs moisture when it is soaked in a liquid. This causes the seed to swell and reach a point where its outer seed coat ruptures and the embryo starts germinating. When we soak seeds, we are simply facilitating this process

Now the question is begging to be asked. Can’t seeds just be soaked in plain tap water? The answer is definitely yes. I have soaked seeds in water that started off lukewarm overnight, and have had reasonable germination rates. After all, the seed swells after the steeping, and that will aid the seed coat to rupture. This, in turn, makes it easier for the seed to germinate

I am, however, not sure that’s all I want to achieve. Instead, I am looking to make sure the seedling stays healthy when it germinates. Using scarification agents like Camomile tea, hydrogen peroxide, seaweed extract, and saltpetre (which all have anti-fungal properties) means any seed-borne pathogens are less likely to attack than if the agents had not been used. Another added benefit these agents provide is that they emulate what happens when a seed passes through a bird’s digestive tract. They act like acids that thin the walls of a seed coat, making it easier for the embryo of the seed to germinate


It wouldn’t have been a proper comparison if I didn’t use some seeds as a control group. I needed something I could judge the performance of the other seeds against. To do this, I decided to use seeds of the same varieties ( Hungarian Hotwax and Bulgarian carrots) that had not been soaked at all for this purpose. I thought the two extremes would make the comparison more marked. The seeds have all been planted, and now it is a matter to wait and see what happens.

Image credit

Alex Popovkin, Bahia, Brazil  / CC BY-NC-SA 2.0  /via Flickr 



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