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When do seedlings need light?

Posted by drayven Texas (My Page) on
Sun, Feb 22, 09 at 16:09

I am starting a variety of herbs as well as some peppers from seed and am very new to all of this. I was told to leave the seeds in dark to help them germinate and after that start using a light.
What I don't know is how soon after germination do I start adding the light?
Do I need to start as soon as they break the surface?

Follow-Up Postings:

RE: When do seedlings need light?

Some seeds need light for germination. What "herbs" do you have?


RE: When do seedlings need light?

Every plant has its own requirements for germination. There are ONLY 20000 different kinds of herbs, so there is no rule of thumb. You'll need to research which ones need light, and which ones need darkness. Packets of seeds bought commercially should have this information printed on them.

Very broadly speaking, and not a rule of thumb, the smaller the seed, the more light it needs. Some need to be just sown on the surface.

For those that need darkness, you should cover the surface of the soil in damp newspaper to keep out the light. It should be removed as soon as the first little leaves emerge. As the seedlings grow, you can gradually increase the amount of light they're exposed to. This is part of the 'hardening off' process.

For capsicums (peppers): Sow seed in early spring once temperatures are consistently over 20C. Cover with 3-5mm of seed-raising mix, transplant seedlings into their final growing positions when they are 4cm high. They must be kept warm to germinate. (ie. they need some light - not complete darkness).

Here is a link that might be useful: growing herbs from seed

RE: When do seedlings need light?

I am growing Basis, Oregano, Parsley, Thyme, Sage, Rosemary, and Bell Peppers inside in starter trays.
It seems like now that they have started to sprout I should start giving them light. Should I start off by giving them the full 18 hours or work up to that?

RE: When do seedlings need light?

Basil, germinates in approx. 7-14 days at 60-70F in well-drained media, sow 1/4" deep.

Oregano, surface sow on well-drained media, germinates in 7-14 days at 72-77F.

Parsley, sow 1/4" to 1/2" deep in rich, moist soil. Germinates in 2-3wks or more.

Thyme, approx. 15-30 days at 55F, sow on the surface, requires light to germinate.

Sage, 9-21 days at 70F, sandy media.

Rosemary, 2 wks to 3 mos at 65-75F, sandy media, 1/4" deep.

Peppers, sow 1/4" deep. Germinates in 2-3 wks at 80-85F.

Be careful not to overwater most of these, keep them moist, not wet.


RE: When do seedlings need light?

I believe these seeds need light to start growing, but thankfully most of these seeds also get all the light they need for there jump start to germination just by sowing them in a lit room, but as soon as any plant starts to sprout they need all the light they can get, so 18 hr to start is perfect.

RE: When do seedlings need light?

All my herbs, veggies, perennials, annuals get started in a dark room. I don't pay any attention to the packet info regarding light for germination. As soon as one or two seeds are up then they all go under lights for 14 hours a day. Light requirements for germination are overstated IMHO. Perhaps light helps but it certainly isn't required for the varieties I grow and I grow all the basics and then some. I cover larger seeds like fennel, tomatoes, peppers, echinacea, etc. but smaller seeds sometimes get lightly covered when they are watered in after sowing. We have been germinating this way for 30+ years.

RE: When do seedlings need light?

Very few seed types need no light at first, when germinating. Some seeds even like cool air with a high moisture content. Once sprouted, light is essential. If its artifical, at least 18 hours per day is needed. Never leave lights on 24/7 as thats too much, as plant leaves do need s short time of darkness too.

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