Artificial light.

[Digger Don]

Winter - no sun - poor growth.
Professionals use mercury vapour lamps to bring plants on I believe, but not realistic for us amateurs.
Has anyone tried using the new LED lamps that are becoming available?
For those that haven't seen them they have 12 to 20 LEDs grouped together, give quite a bright spot light for almost no electricity. ( about 1ma equating to about 160 days fora Kilowatt hour - if my maths are correct )
Homebase have been using them in their small demo lamps for a while now.

What I cannot decide is what the plants like most - heat, ultraviolet, bright light, etc. Supplying heat and the light would be simple but I doubt if the LEDs give much ultraviolet.
If these lamps could be used it would be almost impossible to be any "greener"
Any opinions or, better still, facts.

[Two_Sheds]

If these lamps could be used it would be almost impossible to be any "greener" Any opinions

Well, at the risk of being controversial - the green option is not to use electrickery at all, but to actually grow things in season, ie when conditions are right, not to try and "force" them. I don't want to eat lettuce in February, actually. I want to eat sprouts,kale,Chinese greens,savoy,chard (and I am )

I really, really understand people wanting to sow earlier and earlier. I myself am itching to get planting. As for stealing a march by sowing early - I've tried it. You don't gain much at all, because later sowings generally catch up. EG: Nov sown broadies only crop about 2 wks earlier than Feb sown ones (if they survive the winter that is)

[Geordie]

You are right Digger Don to suggest that professionals use metallic vapour lights, usually metal halide or high pressure sodium lamps. The reason behind this is that plants use different frequencies of light, or different colors of light, for different purposes. Some colors of light make plants grow and bloom, while others promote compact growth, and some aren't really used much at all. For example, the leaves of plants look green because they reflect green light. If a plant reflects a color of light instead of absorbing it, that color isn't used to help a plant grow.

However cost is the prohibitive factor in us amatuers using such lamps, so alternatives are generally sought from the flourescent or LED variety.
I know a little about flourescent lighting so I'll start there.

Fluorescent lights work in two steps. First, electrons stream between electrodes at each end of the tube and produce ultraviolet light, which is in turn absorbed by phosphors coating the tube's inner wall. Those phosphors (substances that emit light when excited by radiation) convert and reradiate the ultraviolet light as visible light. The mix of phosphors determines the color of the light produced.
Fluorescent tubes vary in the color of light they produce, anybody with tropical fish will know tyou can buy different coloured light tubes.

Many different colors of tubes are available. Some are designed to produce specific colors of light, some to approximate sunlight. The color of fluorescent tubes is measured, uaually by the color rendering index (CRI). CRI is a percentage number that measures how closely the light approximates natural sunlight. Tubes with a CRI greater than 90 are considered to be full spectrum.

You really need to use two types of tube for plant growing; cool white, these produce an abundance of light in the blue range, but insufficient red light. The so-called warm white tubes complement them by producing more red light. The blue light promotes root, stem and leaf growth and the red light for flowering.

LED lights should move this process on because they are capable of producing these specific light spectrums without also producing the unused parts of the light spectrum, ie green and yellow. By only using the parts of the light spectrum needed by the plant it has the advantage of not attracting any bugs or pests so is a real benefit to the organic gardner.

It still comes back to the cost / benefit argument whichever light source you want to use but I hope this helps a little way in helping you decide.

[hypnophil]

I understand about plants catching up, but it is nice to have something in the ground or pot to see over winter, not that i grow broad beans, urgh!!
It's good to keep motivated and have a reason to go, which will lead to a bit of weeding, lol, and hopefully keep them down next year.
I had psb, cabbage and cauli, so far the cauli looks like a white/yellow broccoli, the broccoli is purple but not sprouting and the cabbage has i think turned into little flea beetle restaurants!!!!!!

[Digger Don]

Artificial light

Hi,
Thanks for the info and observations. It looks like I will have to try LED lights myself and to that end I have set up a comparative experiment with white light LEDs and a couple of basil seedlings.
If it works will let you know.