Do bigger plants need less light than seedlings?

15 years ago

Hi,

The recommendations for lighting time for little seedlings seem to range from 12 to 16 hours a day. But by the time these plants are ready to go out in the garden, they may only get 8 hours of sunlight. Is this because grown plants need less light than seedlings, or because both seedlings and plants need more artificial light than sunlight? Or some other possibility I am not considering here?

I planning on potting up my Tumbling Tom Reds to their hanging basket soon, but I have no room under my artificial lights for the basket, so I need to wean them off of the artificial lights and onto sunlight-through-southern-exposure-window before I put them in the basket. Not sure if the answer to my question above is necessary in order to deal with my TTRs, but it made me wonder.

Also, any advice on the light weaning and/or potting up a weeping habit plant is, as always, very welcome.

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Comments (8)

digdirt2
15 years ago
because both seedlings and plants need more artificial light than sunlight

Correct. It simply isn't possible to provide the full spectrum and intensity of sunlight with artificial fixtures so we compensate with more time.

I planning on potting up my Tumbling Tom Reds to their hanging basket soon, but I have no room under my artificial lights for the basket, so I need to wean them off of the artificial lights and onto sunlight-through-southern-exposure-window before I put them in the basket.

That will set the plants back. Going from fluorescent fixtures to window light is a step back. ;) The southern window light is even less intense and less full spectrum than the artificial fixtures are, not more. The ideal is to go from artificial light to the outside sunlight, gradually hardening them off to increasing levels of sun exposure.

So the best approach is to first harden them off to the outside and only then transplant to their outdoor basket and the sun just as one would if you were planting them in the garden.

Dave
cleo88
Original Author
15 years ago
Dave,
You are just the person I hoped might answer me!

However, I am sorta stuck with the Tumbling Toms. They are huge and I am running out of room under my lights, but last night it was 33 degrees here.

If I harden them off outside during the day, I can't keep them outside at night. So once they are used to the outside light, I could put them in the basket and then I wuold have to keep pulling them back in every night! I'm obsessive, but perhaps not that obsessive.

I guess I will just pot them up and rotate them into the "good" spots that are directly under the light, and them sometimes they will have to be just near the light.

Let this be a lesson to any newb that wants to start more than 7 weeks from plant out! I thought I could get away with it because most of the first batch were destined for containers, but even then I sorta got put in a tight spot.
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big_ed_pa
15 years ago
I'm curious why south facing window is different from a greenhouse They are both glass.
Ed
ddsack
15 years ago
cleo, I put my tomato seedlings outside during the day many weeks before I would dare to leave them outside during our cold nights -- which I wouldn't do anyway because of the marauding deer which come browsing right up to our deck at night. (Later I have electric fence around my garden.)

Can't you move them into your garage overnight? Or any entryway close to where you will hang them? I have some huge hanging fuchsias that I put on top of overturned buckets so as not to damage the foliage when I put them in the garage during possibly frosty nights.
spiced_ham
15 years ago
4ft fluorescent fixtures put out around 800-1000 foot candles of light (and most of that is in the parts of the spectum plants can't use). Full sun is over 10,000 footcandles, even shade outside is higher than fluorescent fixtures, which is why so many more hours are needed under lights than under full sun.
tn_veggie_gardner
15 years ago
A southern facing window, unless angled towards the sky (like a skylight type window) will only get partial non-direct sun most of the year. It's really common sense if you think about it. The sun rises in the East & sets in the West...neither of those are South.
wordwiz
15 years ago
Dave,

I don't know about your south facing window but mine get quite a bit of direct sunlight at this time of the year. I've measured up to 73,000 lux and it's typical for direct light to come through the window for six hours a day, with indirect light another three.

Mike
digdirt2
15 years ago
Then that must be one he-QQ of a south window Mike as that lux reading is almost 4x the average (depending on the type of glass). But then what is your latitude if you are getting direct from the south sunlight?

Dave

Do bigger plants need less light than seedlings?

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digdirt2

cleo88
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Do bigger plants need less light than seedlings?

Comments (8)

digdirt2

cleo88Original Author

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ddsack

spiced_ham

tn_veggie_gardner

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cleo88
Original Author