Ask a Question forum: seed starting in plastic trays

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Gulleyj
May 17, 2017 9:42 PM CST
I am trying to start several different kinds of seeds in plastic take-out food trays with clear plastic lids. The trays (with lids) are about 2.5 inches tall with the width and length of a book. Some of the seeds are surface sprouters and others are buried 1/4 inch. I moistened the sterile soil thoroughly, sprinkled or planted the seeds as appropriate, and placed the trays with lids in my garden in southern CA. During the day the water condenses on the underside of the lids and drips back onto the seeds and soil so the moisture is constant. After 17 days nothing has sprouted. What's wrong?
Name: Daisy I
Reno, Nv (Zone 6b)
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DaisyI
May 17, 2017 11:00 PM CST
Welcome!

I suspect the seeds rotted due to too much moisture. The humidity needs to be a little bit lower. If droplets start forming on the inside of the lid, the humidity is too high.

Put some holes in the lids of your take-out boxes; if droplets form, crack the lid a bit until the droplets are gone.

I've never thought of putting my seed starting boxes in the garden. I would like to hear how it eventually works. Your seeds will sprout better in the shade though.
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and proclaiming...."WOW What a Ride!!" -Mark Frost

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Name: Mac
Soon to be MidCoast, ME (Zone 6a)
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McCannon
May 17, 2017 11:25 PM CST
In addition, the soil and the seeds may be getting too hot if they're in full sun.
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Name: Baja
Baja California (Zone 11b)
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Baja_Costero
May 17, 2017 11:45 PM CST
I always viewed the droplets on the underside of the clear plastic lid to be a normal result of daily temperature variation, and nothing to be concerned about. They have never caused problems for me. I do not supersaturate.the soil, allowing excess water to exit holes in the bottom (does your container have holes?) but it stays at about 100% humidity and again, not an issue. It could be there's too much water in your containers (if no holes) otherwise the.condensation on the underside of the lid is not likely to be a problem or indicative of a problem. Just a result of a temperature difference between ambient air and the air inside the container, which is pretty much guaranteed over the course of an average day.

As for why your seeds have not germinated, of course it depends on what they are, but be patient and don't throw out your experiment prematurely... things may still happen.
[Last edited by Baja_Costero - May 17, 2017 11:59 PM (+)]
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Name: David Laderoute
Zone 5B/6 - NW MO (Zone 5b)
Ignoring Zones altogether
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DavidLMO
May 18, 2017 12:39 AM CST
Do you have drainage holes cut in the bottom?

Remove lids periodically - you seeds are prob rotting.

Get into partial shade.

Welcome & good luck.
Seeking Feng Shui with my plants since 1976
Name: Rick Corey
Everett WA 98204 (Zone 8a)
Sunset Zone 5. Koppen Csb. Eco 2f
Frugal Gardener Garden Procrastinator I helped beta test the first seed swap Plant and/or Seed Trader Seed Starter Region: Pacific Northwest
Photo Contest Winner: 2014 Avid Green Pages Reviewer Garden Ideas: Master Level Garden Sages I was one of the first 300 contributors to the plant database! I helped plan and beta test the plant database.
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RickCorey
May 18, 2017 12:55 AM CST
Gulleyj said: ... The trays (with lids) are about 2.5 inches tall ...
I moistened the sterile soil thoroughly, sprinkled or planted the seeds as appropriate, and placed the trays with lids in my garden in southern CA. During the day the water condenses on the underside of the lids and drips back onto the seeds and soil ...


Welcome to NGA, Gulleyj. I agree with what's been said so far. If the sealed plastic trays were out in the sun in southern California, they probably got too hot inside for germination, from the greenhouse effect.

Heat will always cause more water to evaporate and "rain" back down than optimum temperatures would. But it is also a clue that your first trays were over-watered. Were there drain holes?

Here's my rule of thumb for gauging soil moisture from what condenses on humidity domes:

just fog or haze: perfect

a few SMALL droplets: OK I guess, but I would crack the dome

many droplets or large droplets: remove the dome, set them on some dry flannel to remove some water, and run a fan to help it evaporate.

enough condensation that any drops run down the side: Darn I over-watered too much again.

Having bottom heat from a warming pad probably increases the symptoms by 1/2 a category. Being left out in the sun might have added a whole category.

>> The trays (with lids) are about 2.5 inches tall

I would think that 2.5" is OK for soil depth, but if that's a dome lid and the soil is only 1.5" deep, that might be shallow for developing seedlings with a few pairs of real leaves. If you are pricking the seedlings out very young, maybe that's enough soil. I don't think I've ever tried shallower than 2", so I don't know.

Good luck next time! It took me 2-3 years to stop killing entire trays of seeds: 11"x21" trays, too! Over-watering is still my biggest mortal sin, but I also confess to starting too many seeds without enough room under lights to "pot them up", starting them too soon or too late, insufficient thinning, lights not bright enough, cooking them in front of a sunny window, chilling them in front of a window at night, and leaving seedlings in small cells too long.

My cat has not yet eaten any seedlings.

Once I tried to start Delphiniums from seed - I think it took me two tries/two years for any seedlings to emerge and survive damping off. For the next few years, they thrived under lights but would mysteriously evaporate as soon as they went outside to be hardened off. It was almost like spontaneous combustion while I wasn't watching.

Finally, after fattening entire generations of slugs who came to worship me as "He Who Brings Us Delphinium Seedlings in the Spring", I learned here at NGA (then ATP) that "slugs really like Delphinium seedlings". THAT led to my growing an actual adult plant at long last:





Imagine how sweet it felt after years of trying! 99% of that was simply: don't over-water, and don't feed the slugs.

I still can't keep myself from over-watering. Now I use "extreme drainage" to protect seedlings from my own over-watering.

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Rather than the above system, maybe your trays would be better sized for just setting on top of some dry toweling or cotton fabric when too wet. (Assuming you have some good big slits or 1/4" holes in the bottoms of your trays.)

There's another style of seed starting, intended to work with a sealed container - just-moist coarse vermiculite in clear tubs with tight-sealing lids. @JonnaSudenius puts them in mottled shade, I think, in a cool climate. Her website doesn't seem to have that tutorial any more.
http://www.seedsite.eu/

I hope you're OK, Jonna!
[Last edited by RickCorey - May 18, 2017 12:56 AM (+)]
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Name: Rick Corey
Everett WA 98204 (Zone 8a)
Sunset Zone 5. Koppen Csb. Eco 2f
Frugal Gardener Garden Procrastinator I helped beta test the first seed swap Plant and/or Seed Trader Seed Starter Region: Pacific Northwest
Photo Contest Winner: 2014 Avid Green Pages Reviewer Garden Ideas: Master Level Garden Sages I was one of the first 300 contributors to the plant database! I helped plan and beta test the plant database.
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RickCorey
May 18, 2017 12:57 AM CST
I see I cross-posted with you, David.

You said it much more concisely!
North Central TX (Zone 8a)
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tx_flower_child
May 18, 2017 11:56 AM CST
Welcome Gulleyj.

@RickCorey - true that you weren't as concise but I'm glad. You outlined many reasons why seeds scare me. I'm working on it tho. Baby steps and all.

@Gulleyj - every time I get some berries in those plastic containers I think, 'hmm. maybe I should save this to try seeds in.' Even tho I think we're talking about different styles/sizes, I'm glad you posted your question. Keep us all updated on your progress.
Name: Philip Becker
Fresno California (Zone 8a)
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Philipwonel
May 18, 2017 2:01 PM CST
Gully 😁Howdy.
#1 Trays do need drainage holes.
#2 😞 where in S Cal ? I think you cooked your seeds with those caps.
Think of a car in sun.
Trays, uncovered, in sun, good ! Bring inside if cold at nite.
Tomatoes and peppers can take 21 days to sprout ! But ! I think there cooked.
Start again. And ! Some of your seeds, may be ready to direct seed.
More Better !😁!
😎😎😎
Anything i say, could be misrepresented, or wrong.
Name: Baja
Baja California (Zone 11b)
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Baja_Costero
May 18, 2017 2:06 PM CST
Here's my usual setup to compare, showing the aforementioned condensation in action, and a bit of recycling too. Smiling These containers are in bright shade (where I like to start my seeds, until they have germinated).

After I water to saturation and let all the water exit the container from below, I put an old plastic lid underneath it (pretty tight fit down there) and plastic wrap on top of it. Evaporation both ways is mostly blocked this way, but the soil is never ever supersaturated. Second picture shows baby aloe trees sprouting underneath. I will leave them under there until they are growing true leaves, then take off the top, then later take off the bottom and begin the stepwise process of gradually moving the seedlings into the sun.

Thumb of 2017-05-18/Baja_Costero/5af439 Thumb of 2017-05-18/Baja_Costero/c404aa

Gulleyj
May 18, 2017 9:39 PM CST
Thanks everyone. Further facts and a follow up question...

The trays have been in partial shade. They do not have holes in the bottom: I thought holes in the bottom would mean I'd need to water them and so the lids would be pointless. That was my thinking anyway. Do you think the seeds are kaput? I'm removing lids tomorrow.
Name: Daisy I
Reno, Nv (Zone 6b)
Not all who wander are lost
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DaisyI
May 18, 2017 9:57 PM CST
I'm voting for kaput. Sorry! Crying
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and proclaiming...."WOW What a Ride!!" -Mark Frost

Webmaster: osnnv.org
Name: Rick Corey
Everett WA 98204 (Zone 8a)
Sunset Zone 5. Koppen Csb. Eco 2f
Frugal Gardener Garden Procrastinator I helped beta test the first seed swap Plant and/or Seed Trader Seed Starter Region: Pacific Northwest
Photo Contest Winner: 2014 Avid Green Pages Reviewer Garden Ideas: Master Level Garden Sages I was one of the first 300 contributors to the plant database! I helped plan and beta test the plant database.
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RickCorey
May 19, 2017 5:58 PM CST
Partial shade helps the "cooking" problem, but begin extra-soggy long enough for them to germinate or die ... if they germinated, they rotted. They may have rotted even if they didn't germinate.

This next may sound like a joke, but I'm at least 60% serious.

The best way to force disappointing seeds to germinate is to start a whole new batch.

It's like they "know" that YOU no longer need THEM, so they become eager to please (and to mess with your head).

If you know you're only going to try once per season, it's like they know that too, and take jerk-pleasure from disappointing you.

Sure, "seed psychology" sounds stupid. But after a few years of them messing with my head, always doing what I least expect, I entertain the hypothesis.

Or maybe there are mischievous garden fairies committed to driving gardeners crazy.

Anyway, gardeners succeed more often if they have fall-back plans like "start a few more trays of easier seeds" or "I may have missed the SPRING sowing, but I can still start a SUMMER crop of beans, tomatoes and eggplant".
Name: greene
Savannah, GA (Sunset 28) (Zone 8b)
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greene
May 19, 2017 6:04 PM CST
Don't know if your seeds are goners or not, but I would start again using just damp vermiculite instead of soil, no drainage holes, tight fitting lids. I learned this method from Jonna Sudenius.

I'll give a shoutout to @abhege.
Sunset Zone 28, AHS Heat Zone 9, USDA zone 8b~"Leaf of Faith"

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