Seeds forum→starting annuals indoors: Deno vs. common take on light for germination--help!

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Name: Jessica
Portland, OR (Zone 8b)
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anoukaimee
Feb 14, 2021 2:42 PM CST
Noob starting ornamental annuals indoor this year, and trying make the most of my relatively small light set up.

I was reviewing Norman Deno's collection of documentation on germination (he collected a lot of experiments on ideal germination conditions, seed priming, and the like, in the 1990s--the collection is available for download on the USDA site here), and while I know it is from over twenty years ago, he's esteemed by JL Hudson and many others, the state of the art in terms of basics hasn't changed drastically (I'm assuming), and he makes a few interesting points that are totally contrary to all other instruction I've read--that could really help me with my space problem!!

The one I'm most interested in and hoping to get some feedback on is the issue of a lot of annuals that are said to require light to germinate not needing light, per Deno. He concedes in certain instances (e.g., clarkia, asarina scandens) germination is faster, but a list of things I'm growing which I've read require light that he says are absolutely fine in darkness:

lobularia/alyssum
cleome
i. balsamina
lobelia
nemesia
torenia

Since space is at a premium (I'm on round two of germinating starting today) I'm trying to make the best use of my lights possible. I'd love to be able to try these seeds without using light better spent on my germinated babies and those seeds that do require light for germination.

Does anyone have any feedback on trying these indoor, from seed, in the darkness? Or an informed opinion about this? Truly appreciate any help that can be given.

For anyone not familiar w/ his collection and interested, it's available for free download on the USDA website: https://naldc.nal.usda.gov/?ut...
Name: Karen
Cincinnati, Oh (Zone 6a)
Forum moderator I was one of the first 300 contributors to the plant database! Cut Flowers Winter Sowing Charter ATP Member Seed Starter
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kqcrna
Feb 15, 2021 7:17 AM CST

Moderator

No, I haven't done it in darkness. But I have wintersowed some of them (outside, in winter, in milk jugs) with success.

Karen
Name: ZenMan
rural Kansas (Zone 5b)
Kansas 5b
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ZenMan
Feb 15, 2021 12:34 PM CST
Hello Jessica,

"Since space is at a premium (I'm on round two of germinating starting today) I'm trying to make the best use of my lights possible. I'd love to be able to try these seeds without using light better spent on my germinated babies and those seeds that do require light for germination."

I "sort of" responded to your post over at Houzz GardenWeb. I will try to do a better job here. It should say on the seed packet whether its seeds need light to germinate or not. For example, Lettuce seeds, at least some of them, do need light to stimulate germination, so you should sprinkle lettuce seeds on the surface of the growing medium and simply press down with something flat to get them in good contact with the growing medium, while letting them receive light.

But lettuce is kind of a special case. I grow (and breed) zinnias as a hobby, and it doesn't say anything on their seed packets about them needing light to germinate, and it usually says to cover them with 1/4 to 1/2 inch of soil, so they would be "out of luck" if they needed light to germinate. I germinate my zinnias indoors in 3-inch pots containing Premier Pro-Mix (hand shredded to make it suitable for seed starting) under T8 fluorescent lights (admittedly now obsolete, but still quite functional). The light warms the surface of the Pro-Mix, which is beneficial for germination, and as soon as the zinnia seedlings emerge in 2 to 6 days, they immediately do need the light for photosynthesis and healthy growth.

" obularia/alyssum, cleome, i. balsamina, lobelia, nemesia, torenia "

I seem to recall there is something tricky about cleome germination, but I have no experience or first hand information about any of those. But I doubt there is any significant opportunity to skip lights for any of those, because they all will need lights pretty much immediately after germination.

I purchased a paper copy of the Deno documents several decades ago from his son, who had a bunch of the documents in his garage. Apparently when he was alive Deno was seeking to expose some "old wive's tales" about specific seed germination. He also had done a lot of experiments using Gibberellic Acid to stimulate germination of various species. But that was all decades ago, and the Internet is now a better source of germination information. Unfortunately, there are still some old wive's tales on the Internet, but many of those are also exposed on the Internet.

Perhaps you should save your pennies and buy some more lights.

I recommend this book as a good source of information on growing under lights. My lettuce information came from it. Thumbs up

https://www.amazon.com/dp/1604697954/

ZM (not associated with any product or vendor mentioned or linked)
I tip my hat to you.

Name: Jessica
Portland, OR (Zone 8b)
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anoukaimee
Feb 17, 2021 12:35 AM CST
ZenMan said:Hello Jessica,

I "sort of" responded to your post over at Houzz GardenWeb. I will try to do a better job here. It should say on the seed packet whether its seeds need light to germinate or not.

Hey Zenman, Great to see you here, too!

" obularia/alyssum, cleome, i. balsamina, lobelia, nemesia, torenia " ...I seem to recall there is something tricky about cleome germination

I'm all set on the cleome. Basically, it requires (or at least does better with) two weeks of cold stratification. I'm going to put the soil blocks directly in the refrigerator for 2 weeks. The other alternative is oscillating temperatures, but I think it's easier just to stick it in the fridge for 2 weeks.

Apparently when he was alive Deno was seeking to expose some "old wive's tales" about specific seed germination. He also had done a lot of experiments using Gibberellic Acid to stimulate germination of various species. But that was all decades ago, and the Internet is now a better source of germination information.

That's true, and that was my concern. Deno was not a horticulturalist or a botanist, he was a chemist. That said, much of his research is still well regarded by people knowledgeable about seed starting, such as JL Hudson (nb: he sells GA3, but I also can say, even as a skeptic, that he seems to be an honest broker and extremely knowledgeable... Unfortunately he doesn't entertain individual inquiries).

this book as a good source of information on growing under lights. My lettuce information came from it. Thumbs up

https://www.amazon.com/dp/1604697954/


I'm fairly sure that I have a copy of that book actually, I will take another look at it.




Thanks, Zenman! You've been very generous with your knowledge. Thank You!
Name: Caroline Scott
Calgary (Zone 4a)
Charter ATP Member Plant Lover: Loves 'em all! Peonies Lilies Enjoys or suffers cold winters Winter Sowing
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CarolineScott
Feb 24, 2021 9:55 AM CST
Cleo me likes alternating temperatures.
Here in the cold north, I sow it outside so the seeds experience temperatures below freezing and above.
West Central Minnesota (Zone 4a)
Rubi
Mar 6, 2021 3:31 PM CST
Save all your space under your lights for seeds that are germinated. My experience is that seeds that claim to need light for germination don't benefit noticeably from higher intensity light. They'll still come up with just normal ambient light. The instant the seeds come up though, you'll need lots of light or they'll be weak and leggy. If you don't have enough space for all your seedlings, the ones without supplemental light are going to suffer after they come up. I bet if you did a germination study, you wouldn't get significantly better rates with seeds under the lights than ones just near a window

Edit: I just read your list again. I just started some allysum and gave them no extra light and I actually covered the seeds. The seeds were several years old and I didn't expect much, but I probably got 1/3 of the seeds to germinate with no supplemental light. Maybe they all would have grown with light, but I wasn't going to be surprised if none of them came up since the seeds were many years old.
[Last edited by Rubi - Mar 6, 2021 3:37 PM (+)]
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Name: Rick R.
Minneapolis, MN, USA zone 4
I was one of the first 300 contributors to the plant database! Garden Sages The WITWIT Badge Garden Photography Region: Minnesota Hybridizer
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Leftwood
Mar 6, 2021 4:42 PM CST
I am with Rubi, here. While there has been testing more recently, even with differing wavelengths of light for germination that are significant, for the most part for us regular gardeners, it's way to involved to be applicable for our use. For the most part, I think you will find good bright light as effective as more intense artificial light.

You will likely find, though, that under artificial light (as opposed to bright ambient light), the temperature will be warmer and seeds should germinate faster because of that. (Higher temperatures increase the rate of chemical reactions and therefore growth.)
When the debate is lost, slander becomes the tool of the losers. - Socrates
Name: Caroline Scott
Calgary (Zone 4a)
Charter ATP Member Plant Lover: Loves 'em all! Peonies Lilies Enjoys or suffers cold winters Winter Sowing
Bulbs Region: Canadian Garden Ideas: Master Level Million Pollinator Garden Challenge
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CarolineScott
Mar 9, 2021 12:38 PM CST
If you are not sure and have lots of seeds .....do half the seeds one way and the other half another way.
Learning to grow a given plant under your conditions is open for trial and error too.

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