AusBonsai

I was curious to know why we need to soak seeds in warm water for 24 hours prior to sowing or stratifying? Does this mimic anything in nature, or is it just a way to "break" the shell of the seed to save time? I've read the seeds that float are not "viable" and the ones that sink are fertile seeds? why is this? Also can you soak the seeds for 24 hours and then not sow or stratify them for a month or two?
I know that is a lot of questions, but if you don't ask, you don't learn.
Thanks guys and girls
Luke

surely someone out there has an answer, or at least a theory???

My interpretation of it is so that we can identify and eliminate dud seeds. They tend to be hollow inside and so they do not sink. But I still do not understand what made the good seeds sink?

Do they actually absorb water or what?

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The following story is true. Two years back, a friend bought for me 5 baobab seeds from a seller in NSW. They came with instruction. Boil water, pour onto the seeds. Leave it overnight. And sew the next day.

Four germinated. But did not survive the winter.

Hi Luke, Soaking seeds in warm water speeds up the process of moisture absorbtion which they need to do in order to activate germination processes. It is not strictly needed but usually useful. Some seeds with a hard coating such as Acacia must have there seeds soaked in hot water or abraised (scarified) in some way before they will germinate. Most cold climate seeds need to be stratified 4c for about 3 months for good germination. They should be soaked overnight in warm water before moist stratification in the fridge. Once you soak seeds you MUST either stratify or sow.
Yes floating seeds are usually unviable

your a bit of a worry Luke, do you ever search for things mate ,

http://www.rain.org/~sals/soak.html

Hi Luke,

It's good to ask questions! Particularly ones that many others simply overlook such as this.

As mentioned above, there are several reasons for soaking seed. But really the important thing for EVERY seed is that it needs to be moist to germinate. "Respiration" is the process that unlocks energy. Respiration occurs in all living things. In the case of animals and plants, respiration occurs using oxygen to break apart molecules and release the energy that we can then use. It is why we need to breath - so that we can break down the food we eat to produce energy. Respiration can ONLY OCCUR at moist sites where (in most cases) oxygen comes into contact with these other molecules (in plants mainly glucose - a type of sugar). If the site is dry, it cannot break apart this molecule and no energy is released. The big white part in most seeds is complex carbohydrates. The hydration of this allows it to convert to glucose and respiration to occur. The process of the seed being wet and then respiring is called imbibition.

If I didn't explain that too well, you can google the term "imbibition" or ask on here what you are unsure about.

Joel

Here is a video that goes into it a bit more. Enjoy!

http://www.youtube.com/watch?v=tPMjVVGLEZM

Thanks for your answers everyone, much appreciated.

Craig wrote:your a bit of a worry Luke, do you ever search for things mate , http://www.rain.org/~sals/soak.html

In answer to that Craig, yes I do search for things, but in this case I only came across HOW-TO soak seeds, rather than WHY we soak seeds. maybe I should have tried a different combination of wording in google. I always search on this forum before I post, but I think the search function could be improved slightly. eg I was searching on google for some info on seed germination, and found a post by "JAPH" on AUSBONSAI but I couldn't view the pics because I wasn't logged in. So I "cut" the topic name, and logged in to Ausbonsai and then "pasted" the topic into the search bar. Only problem was it didn't find it, and I had to go through about 10 pages to find out it wasn't there. I ended up searching Japh's posts and found it eventually. I'm not particularly smart when it comes to computers, but I thought search functions were supposed to save time??

Joel wrote:Hi Luke,

It's good to ask questions! Particularly ones that many others simply overlook such as this.

As mentioned above, there are several reasons for soaking seed. But really the important thing for EVERY seed is that it needs to be moist to germinate. "Respiration" is the process that unlocks energy. Respiration occurs in all living things. In the case of animals and plants, respiration occurs using oxygen to break apart molecules and release the energy that we can then use. It is why we need to breath - so that we can break down the food we eat to produce energy. Respiration can ONLY OCCUR at moist sites where (in most cases) oxygen comes into contact with these other molecules (in plants mainly glucose - a type of sugar). If the site is dry, it cannot break apart this molecule and no energy is released. The big white part in most seeds is complex carbohydrates. The hydration of this allows it to convert to glucose and respiration to occur. The process of the seed being wet and then respiring is called imbibition.

If I didn't explain that too well, you can google the term "imbibition" or ask on here what you are unsure about.

Joel
Here is a video that goes into it a bit more. Enjoy!

http://www.youtube.com/watch?v=tPMjVVGLEZM

Thanks Joel, that explains a lot, it is quite fascinating to see that seeds can lift 10.5lbs!! I am guessing that in nature seeds dry out during their dormancy, and then during winter, they absorb enough moisture from rain, and or the ground to imbibe naturally? By pre-soaking seeds we are just speeding up nature

Fair call Luke , the keywords do relate to what info you find. On this site like you found out, if you know the poster it can be alot quicker to locate the topic, keep the keywords simple here tho, eg;like seeds or soaking.

Joel wrote:It's good to ask questions!

Does anyone know why rubbing seeds between sandpaper before soaking them is a good idea???

VelvetSicklid wrote:Does anyone know why rubbing seeds between sandpaper before soaking them is a good idea???

I believe that is only recommended for hard shelled seeds eg Illawarra flame tree. It is to help weaken the shell of the seed to speed up the germination progress. A lot of seeds don't require this, eg maples, liquidambar, JBP, Stewartia, Ficus, Callistemon, Eucalyptus etc It is only on the larger hard coated shells. Apparently you can "nick" them with a knife too, or use nail clippers to snip a tiny bit off the end. I have tried these methods, but had no success. Hope that helps, but maybe someone else can chime in with a more detailed answer?

On one of Sir David Attenborough episode, he talks about North American squirrels; who eat oak seeds or something like that.

He mentions that these seeds, because they are so thick, it will takes quite a few years in the elements for the shells to break down and finally germinated. That is if the squirrels do not get to them first.

Macadamia nuts in QLD fall to the ground which can then be collected and eaten. They shells are so hard to break. I used clamps to break them.

( I do not know which animals in Australia actually eat macadamia nuts.)

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A little while back, the ABC ran a documentary on The Doom Day Vault, a collaborative thing between nations. The documentary features an Australian scientist, Dr. Ken Street. Who goes around remote parts of the world to collect original peas. The seeds are kept in a secret vault in one of the Poles. This vault is built with such strength that it can withstand nuclear attack. I think title of the show was "The Seed Hunter".

I cannot recall if they mention how they store the seeds for. Or how long the seeds can remain viable under such conditions.

Does anyone know why rubbing seeds between sandpaper before soaking them is a good idea???

Luke's right this only applies to some types of seeds. The ones that have very thick or waxy coats. The plants that have developed these seeds usually live in harsh climates. If all the seeds germinated with the first rain its likely that a following dry spell would kill all the seedlings so a waste of time and energy from the plant's point of view. Coating the seeds delays germination - only a few germinate when they first get wet. Again, from the plant's point, If they survive that's good but if they don't no great loss. As time goes by the coatings are abraded or dissolve or are cracked by heat and more of the seeds can germinate. Eventually some will germinate at a time when follow up rain ensures survival and the strategy has paid off.

As plant growers we do not want to wait for months or years for the seedlings so we look for ways to break the coating. For just a few seeds I tip them on smooth concrete or a brick, put a fingertip on a seed and drag it across the rough surface to scratch the coat. Boiling water is easier for larger numbers - put seeds in a mug, boil the jug, pour hot water over seeds. I usually leave them to soak overnight (and for the water to cool) but you can sow right away and the seeds will absorb moisture from the mix. I find filing and nicking seed very tedious so do not use these methods. You could also try putting seeds in a container with dry sand. Shake well every day for a week or let the kids play footy with it for a few days. The sand should scratch enough seeds to get good germination.

Don't you just love nature? and seeds in particular.

re- sandpapering or nicking seeds

Use the force luke, and may the force be with you

banksiaman wrote:re- sandpapering or nicking seeds

Use the force luke, and may the force be with you

If only I had a dollar for every time I have heard that. Ive heard that so often, I think I owe George Lucas a swift kick in the testes.