Do seedlings need darkness at all?

[Chef_uk]

Probably a stupid question but was wondering if seedlings need the dark like other living life does to recharge its batteries as such or if they had 24 hour sun, would thrive the most, grow the most, and produce the most?

[binley100]

TBH haven't a clue but I know that some seeds need light to germinate ........

[gojiberry]

All depends on the seed. Some require light and some don't. The seed packet will tell you if the seeds need light to germinate. It is usual for seeds requiring light to have a light sprinkling of fine grade vermiculite sprinkled over them as it keeps the seeds warm but allows the light to get to the seeds.

Ian

[Kristen]

Probably not the answer, but up in the Arctic Circle they get 24 hours light (and 6 months darkness too of course ...).

Under grow lamps I give mine some darkness, but lamp is on from 10pm to 7am, and they have daylight from 7am to 6pm ... so only 3 or 4 hours

[bingo]

Hi,
this is an excerpt from "how to germinate seed"
How to Germinate Seed

LIGHT or DARKNESS: Some seeds need light to germinate; others need darkness, and light prevents sprouting. If light is required, sow on the surface; if darkness is needed, cover seed well.

[bazzaboy]

Chef uk, if you're asking about the growth rate of seedlings rather than prompting the germination of seeds I believe the answer to be that they do benefit, like the rest of us, from a daily period of slowdown/darkness..... There's some great stories (which I believe to be true) associated with this, particularly onions which, it is claimed, put on leaf whilst daily daylight is increasing but as soon as they sense they have passed the longest day switch to building up a food supply (i.e. the onion). Clever critters onions!

[Chef_uk]

yes that was what I was asking, sorry for wording it wrong and confusing peeps. Interesting info on the onions though

[Two_Sheds]

wondering if seedlings need the dark

That's a really good, interesting question. Plants do grow in the dark (at least for a while), as anyone will know who's tried to kill weeds by covering them with a mulch, or has covered rhubarb to force it, or has germinated seeds in the airing cupboard

Apparently wheat never needs to sleep, but tomatoes do: http://www.usu.edu/cpl/PDF/Instructi...warfPlants.pdf

Here's a fun link: Do plants have body clocks? - The Naked Scientists November 2008

[Kristen]

particularly onions which, it is claimed, put on leaf whilst daily daylight is increasing but as soon as they sense they have passed the longest day switch to building up a food supply (i.e. the onion). Clever critters onions!

Oh!Oh! I've been putting my onions under the growing lamp at night (and I already knew about day-length and Onions - its one of the few crops that won't "catch up" if sown late, because of that - so I have no excuses ).

I'll stop giving them extra light and hope no-harm-done ... fingers-crossed

[bazzaboy]

Interested to hear what happens, Kristen, I think they’ll be ok… For the reasons you outline the pundits say start onion seed about Christmas time and that fits with the leaf/body theory as daylight beginning to lengthen (which I’ve always assumed is why Christmas is placed when it is but that’s another story). But in January daylight is only about 8 hours a day at best so a bit of supplementary can be helpful, say up to 11 or 12 hours total (but not all night or you’ll have exhausted onions ). By mid-March (any time now) daylight will have increased to nearer 12 hours a day at which point the day-glo can thankfully go back in the cupboard until next Christmas…!

[Kristen]

By mid-March (any time now) daylight will have increased to nearer 12 hours a day at which point the day-glo can thankfully go back in the cupboard until next Christmas…!

I'm growing to my sowing schedule, that I have been using for several years. Previously I have been pricking out and putting in blow-aways in the unheated conservatory, and bringing in on really cold nights.

This year I have been bringing in and putting under lights (first year I've had a light) and it seems to me that it is a) much lower light level than previous years and b) much colder

We haven't had much frost, but its feels cold and dank.

If I hadn't had the lamp I think I would have had some leggy plants this year ...

[Snadger]

Interesting question. Plants need sunlight for photosynthesis to grow. If they have 24 hour daylight and all other things being equal temp, fert, soil moisture etc, theoretically they should grow much faster!

Or am I wrong?

[bazzaboy]

I suspect the answer across ALL plant-life varies considerably, Snadger, though I was only talking about alliums where the ratio of light to non-light seems to trigger an effect. There is also a suggestion that it is actually DARKNESS that prompts some plants to flower – see for example
Light and its use by plants
so perpetual light would confuse rather than hasten them!
Perhaps plants need their dreams too?