Tomato Seed Storage with Silica Gel

coolbythecoast · February 22, 2018

I am storing my tomato seeds in an airtight glass jar with a goodly amount of Silica Gel with the intent to extend the life of the seeds. I read that good storage conditions are met when the temperature in Fahrenheit added to the Relative Humidity results in a sum that is less than 100.

But is there a thing as too dry? I have heard of a thing called 'hard seed' where the seed is so dry that it has trouble taking in water for germination, but this is mostly said of large seeds and I assume that the only harm is delay in germination. What I don't know is if it is possible to actually harm my tomato seeds by being overly dry. My humidity indicator strip registers 10% humidity or less.

And what about the combination of Silica Gel and storage in the refrigerator?
With 10% humidity in the jar, does storing in the refrigerator change things?

Thanks,
Gary

Tiny Tim · February 22, 2018

Gary, I use a 30 gram silica pack for my wooden seed box. I haven't noticed any issues with that. I have read on other forum pages of people freezing seeds in jars and still have viable seed 3-4 years later. I believe it had more to do with consistent temp/humidity. Large swings, if I remember correctly had the lowest germination rates.

PhilaGardener · February 22, 2018

There is supposedly a "too dry" for legumes but I don't know for tomatoes. Hopefully someone else will chime in!

KarenO · February 22, 2018

I do think dessicating seeds completely is harmful, potentially fatal for the embryo.
I will look for more information and post if I find it,
KarenO

Tiny Tim · February 22, 2018

Karen, I have seed from last year that was stored with this very pack. I only started 6 seed.. All six were up in 6 days.

KarenO · February 22, 2018

I think the upshot if what I am reading is that silica gel is great for drying seeds but should not be left in a closed airtight container with seed once they are dry in storage. The box would be fine I think because it’s wood and not airtight.
KarenO

Tiny Tim · February 22, 2018

Karen, Cigars as well as tobacco are stored in jars and or air tight containers with these. The sole purpose is to keep those cigars at 69% moisture content.
I was gifted these. I don't smoke so still have them.
This company makes a variety of moisture control products.
If the OP want's to find a happy medium he may want to try these. Amazon sells them for about $15.00 for a 10 pack of the 8 gram size.

KarenO · February 23, 2018

Over dried seed is more difficult to germinate and there just is no real need for it unless you store your seed in a humid environment but in that case I think the silica would only hold so much moisture as well.
Cool and dry storage of seeds properly air dried has always given me excellent results without need of silica. The fact that professionals don’t use it in their packaging helps me to know that while it’s likely not a big problem it’s not necessary either.
KarenO

Worth1 · February 23, 2018

I store my seeds in the most adverse conditions known to man and they sprout well after ten years of being kept this way.

Worth

coolbythecoast · February 23, 2018

It turns out that seed damage from excessive drying is a hotly debated area of discussion. The international standard is to dry seeds at 15% RH, but now it is suggested that this may be a bit too low and the consensus is that 20% RH is a good compromise. But 15% can't be that bad if it has been used world wide for years.

Other info tends to disagree that there is much of a problem: "If an excess of beads is stored with seeds, the seed moisture content will be reduced to very low levels, most desiccation-tolerant (“orthodox”) seeds are not damaged even when dried to 3-5% moisture" says the manufacturer of seed beads desiccant. I can't find the exact relationship between RH and seed moisture percent, but it seems like seed moisture percent is about half of RH storage, so 10% RH may possibly result in 5% seed moisture.

Here is another comment on dry seeds:
"I don't think it is possible to over dry seeds without over heating them. I know a guy that runs a survival seed business and discussed the research with him. I don't remember the exact number, but he dries seeds to low single digit relative humidity. He built a special cold dryer to do it."

So far I have stored my tomato seeds with silica gel for several years and have very high germination rates. Packs dated 2010 seem to germinate fine. I guess I will continue with the gel until I notice a problem, I assume any damage must be gradual and I can increase to 20% RH at that time if there is a problem.

coolbythecoast · February 23, 2018

Here is a slide presentation of using Zeolite on rice seeds, the info may mostly apply. In their experiment they could dry the seeds as low as 8% moisture content with silica gel and as low as 6% with Zeolite. Their target was 6% as the optimum seed moisture content, so I infer from this that you can not over-dry small seeds when storing with silica gel.

https://www.seedtest.org/upload/cms/...-2b-Timple.pdf

Koala Doug · February 23, 2018

I store my long-term seeds (those that I won't be getting back to for 5 or more years) in a glass mason jar in the back of a freezer with a few desiccant packs. The seeds were properly fermented and dried prior to long-term storage. And I also transfer the jar to the refrigerator for a day and then at room temperature for another day before opening it to avoid the condensation affecting the seeds.

coolbythecoast · February 26, 2018

Koala, seems good to me, pretty much what I do and so far, so good. I can only add that you can't tell by looking if the silica gel is still active. So recharge the packs at 250 F and you can put a humidity indicator card in the jar so that you can be assured that your seeds are still dry.

I find that a lot of manufacturing companies receive both items accompanying their purchases, so you may not have to buy them if you check around a little.

February 22, 2018	#1
coolbythecoast Tomatovillian™ Join Date: May 2007 Location: SoCal Posts: 39	Tomato Seed Storage with Silica Gel I am storing my tomato seeds in an airtight glass jar with a goodly amount of Silica Gel with the intent to extend the life of the seeds. I read that good storage conditions are met when the temperature in Fahrenheit added to the Relative Humidity results in a sum that is less than 100. But is there a thing as too dry? I have heard of a thing called 'hard seed' where the seed is so dry that it has trouble taking in water for germination, but this is mostly said of large seeds and I assume that the only harm is delay in germination. What I don't know is if it is possible to actually harm my tomato seeds by being overly dry. My humidity indicator strip registers 10% humidity or less. And what about the combination of Silica Gel and storage in the refrigerator? With 10% humidity in the jar, does storing in the refrigerator change things? Thanks, Gary

February 22, 2018	#6
KarenO Tomatovillian™ Join Date: Oct 2012 Location: Vancouver Island Posts: 5,922	I think the upshot if what I am reading is that silica gel is great for drying seeds but should not be left in a closed airtight container with seed once they are dry in storage. The box would be fine I think because it’s wood and not airtight. KarenO Last edited by KarenO; February 22, 2018 at 10:19 PM.

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February 22, 2018	#2
Tiny Tim Tomatovillian™ Join Date: Feb 2018 Location: Near Albany,NY Posts: 90	Gary, I use a 30 gram silica pack for my wooden seed box. I haven't noticed any issues with that. I have read on other forum pages of people freezing seeds in jars and still have viable seed 3-4 years later. I believe it had more to do with consistent temp/humidity. Large swings, if I remember correctly had the lowest germination rates.

February 22, 2018	#3
PhilaGardener Tomatovillian™ Join Date: Jan 2014 Location: Near Philadelphia, PA Posts: 1,940	There is supposedly a "too dry" for legumes but I don't know for tomatoes. Hopefully someone else will chime in!

February 23, 2018	#8
KarenO Tomatovillian™ Join Date: Oct 2012 Location: Vancouver Island Posts: 5,922	Over dried seed is more difficult to germinate and there just is no real need for it unless you store your seed in a humid environment but in that case I think the silica would only hold so much moisture as well. Cool and dry storage of seeds properly air dried has always given me excellent results without need of silica. The fact that professionals don’t use it in their packaging helps me to know that while it’s likely not a big problem it’s not necessary either. KarenO

February 23, 2018	#9
Worth1 Tomatovillian™ Join Date: Feb 2006 Location: Den of Drunken Fools Posts: 38,539	I store my seeds in the most adverse conditions known to man and they sprout well after ten years of being kept this way. Worth

February 23, 2018	#12
Koala Doug Tomatovillian™ Join Date: Dec 2017 Location: Detroit Posts: 688	I store my long-term seeds (those that I won't be getting back to for 5 or more years) in a glass mason jar in the back of a freezer with a few desiccant packs. The seeds were properly fermented and dried prior to long-term storage. And I also transfer the jar to the refrigerator for a day and then at room temperature for another day before opening it to avoid the condensation affecting the seeds.

February 26, 2018	#13
coolbythecoast Tomatovillian™ Join Date: May 2007 Location: SoCal Posts: 39	Koala, seems good to me, pretty much what I do and so far, so good. I can only add that you can't tell by looking if the silica gel is still active. So recharge the packs at 250 F and you can put a humidity indicator card in the jar so that you can be assured that your seeds are still dry. I find that a lot of manufacturing companies receive both items accompanying their purchases, so you may not have to buy them if you check around a little.