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how much light for seedlings?

Posted by kawaiineko_gardener 5a ( on
Thu, Dec 27, 12 at 18:04

I am basically referring to seedlings being grown for transplants. I need to know how many hours per day you give them with light you would give them initially (i.e. after they've germinated and when they're 'newborne seedlings')

I also know you gradually reduce the amount of light they receive per day until it's to the point that it mimics the duration of light outside to get them used to outdoors conditions.

The seedlings would be tomatoes, eggplants, cabbage, broccoli, lettuce, cauliflower, and lettuce. Possiby beans, corn, peas, and okra, but I don't know yet with these.

By how much would you reduce hte light by and when would you start doing this? HOw old should the seedlings be when you do this? How often would you reduce the light (weekly, monthly etc.)

I know very little about growing seedling transplants so I could really use help with this.

THey will be grown under a grow light.

Follow-Up Postings:

RE: how much light for seedlings?

16 hours is pretty much the standard recommendation but that all depends on the type of light used and how high their output is. "A grow light" won't cut it for more than a couple of plants. Read the FAQs here on lighting.

As for "gradually reduce the amount of light they receive per day until it's to the point that it mimics the duration of light outside to get them used to outdoors conditions" - that isn't really true as the outdoor light will always be more intense than anything you can produce indoors.

What that means to most is that IF you have good natural light such as in a greenhouse then as the days get longer you don't have to leave the light on as long and can cut back to 10-12 hours. Without a greenhouse it is pretty much impossible to give them too much light.

Since most seedlings are started only 6-8 weeks before transplant time it is the last 7-10 days of proper hardening off that gets the plants ready for the outdoors, not the lights.


RE: how much light for seedlings?

I agree with Dave. Simply put, you need the lights very close to the plants, so if you're using grow lights, you'll need a lot of them or a fluorescent tube fixture so you can fit all the plants close to the lights. I also use 16 hours of indoor light.

When it's time to plant outside, you harden them to that light gradually, outdoors, over a period of a week, giving them more and more time in the direct sun each day, starting with about 15 minutes, the rest of the time in the shade. No need to deal with changing the indoor light time.

As an aside, what counts most is air circulation around the plants to prevent fungus killing them. Have fun with it!

RE: how much light for seedlings?

Well the grow light I plan on using is a 3 tier one. I did look up a thread on what type of light to use for starting seedlings. They recommended it be between 5500k to 6500k with the brightness.

I then looked up the product info from the place I'm debating getting the light system from.

This is an excerpt straight from their site regarding the description of their lights

113 micromoles (no clue what that is but it's in regards to light intensity).

It's a 'cool'light and contains 6500k; they use high spectrum lights, and the bulbs themselves are T-5. I believe two bulbs are used per tier.

Would this suffice for growing seedling transplants?

Also I would love to be able to do this on a cheaper scale.
What type of lights would you recommend. Please provide clarification with abbreviations descriptions etc. with what type of light to use for starting seedlings, as I really know nothing about them.

I can't really affix any attachments into the ceiling. Do you know of any online gardening supply companies that specialize inthis?

I would like to make a tiered system, how would I go about doing this and what equipment would I need? It would be a three tier shelf, with three lights per shelf if I were to make it myself.

Needs to be simple to set up, as I'm NOT a do it yourself person; i.e not that I don't want to, rather I'm not good with that sort of thing.

RE: how much light for seedlings?

The FAQ here explains all about using just plain 4' shop lights with standard T8 bulbs bought at Walmart or Home Depot etc. That is all most use and the least expensive way to go. And if you search 'light set-up' here and especially over on the Growing Under Lights forum (linked directly from this forum's page) there are all kinds of pictures people have posted showing their home-made lighting set ups.

Most any of the gardening supply or greenhouse supply online sites offer all sorts of lighting set ups.


Here is a link that might be useful: Light set up discussions

RE: how much light for seedlings?

I bought my grow light setup from Park Seed catalog. It's two levels, 8 trays, and stands on its own. I had to add two more shop lights to it (one on each level isn't enough light), which was simple to do with a drill and some chain you can get by the foot at Lowes.

The setup has 4 40" fluorescent shop light fixtures, two on each level. Each fixture has a regular fluorescent tube and a full spectrum light tube. Grow-light tubes are expensive, and the full spectrum works fine. Get them at Lowes also.

I've used this setup for over 25 years and have replaced bulbs rarely. I can raise and lower the lights with the adjustible chains. It fits in the corner of a room. Now that I'm older and don't want to kneel down all the time, I have propped up the whole thing on four 5-gallon buckets.

Hope this helps!

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