Grow Light germination ?

http://gardenerscorner.co.uk/forum/general-gardening-discussion/1199-grow-lights.html

I have just been reading the post above on Grow-Lights . I was considering this on a very very small scale - I am not planning a cannabis farm ! You can buy LED 14w red blue units for £21 , but I would not trust the reliability of these ,i.e bursting into flames when we are at work :wallbang:
All I would like to do is improve seed germination on a few plants and raise them to say the first true leaf stage . Would a small fluorescent clip on aquarium light 12w, just 2" over the seed tray, in a basic light box give any advantage ?

TIA

 

Sorry Harry, this is just an inane comment so that I can keep an eye on this!

 

I keep reptiles and some have the same requirements for sun light!
pet shops sell a tube same fittings as a fish tank,but much higher output of uv about £25 run that on a timer 12 hours a day.
But even if you do all this and raise plants early unless you intend to carry on growing them indoors they will be harder to acclimatise to natural conditions.
IMHO better to work with nature you wont beat it,nature will always win in the end!:WINK1:

 

I have run the light box above for several years and found it to be excellent. The key is the actual level of light. Its got to be pretty high if you are to get active growth. I have done a bit of research and the general feeling is that you need a minimum light level of about 3,000 lux (measure of light intensity) but preferably more. This compares with your average lit sitting room at night which might be 50 lux. The above box produces about 10,000 lux at plant level, which I can measure with a light meter. 10,000 lux is roughly equal to a summers day. Its less that the maximum daytime levels outside in summer, but it is constant for 14 hours a day (on a time switch) whilst daylight is lower in the early morning and late evening and when cloudy.

To get 10,000 lux, I have three 3 feet long fluorescent tubes suspended over a growbag tray (100 x 39 cms). ie 90 watts in all. The lights are lowered to within a 2 or 3 inches of the tops of the plants, as light levels fall off with distance. I also enclose the whole lot in a white walled box to minimise losses. I go away, sometimes, for 2 or 3 weeks at a time and am happy to leave it switched on.

You can pro-rata the dimensions for a lower light level. My feeling is that three tubes gives a more even light distribution than just one tube. In my box I have a heated propagator (summer heat levels to go with summer light levels). And I can alter the height of the lights - but I usually don't!

My own experience has been very good. In the first year I sowed some Salvia coccinea seeds in November, and found them in flower in early January. Its excellent for both seeds and cuttings.

A lot is talked about special (expensive) growing bulbs and spectral profiles, and it may be that if you are a professional grower that last 10% is the difference between profit and loss. But the sun, which has a good reputation as a light source for growing things, has a wide spectrum, and so I believe that any light source with a similar wide spectrum will work.

 

That looks very much like the 57cm x 36cm Sankey thermostically controlled propagator I have. I'm thinking about getting one of these lights to go over it (almost identical size) - any thoughts?

Grow Lamps

 

Scrungee - that light looks excellent. Its about the same wattage (and hence light output) as mine but over a slightly smaller area - so even more powerful. I have Googled it and I see it at £80, which is not a bad price. I doubt you could buy 4 two feet tubes and fittings for any less.

I see the unit is offered with 6,500k (slightly blue light) for vegative growing and 2,700k (red light) for flowering plants. This compares with the sun at 5,500k (white light). I don't doubt their information - someone has obviously done the research. However I would like to see some explanation and evidence that different temperature lights are better than sunlight. And how much improvement there is.

 

£68.95 +£6.25 P&P at Jungle Seeds - Grow Lamps is where I considering getting it from, but I dont see options of different bulbs.

Can I assume from the info in the quote in my post above that it's got the 'blue' bulbs?

 

I read the name Light Wave on your picture and Googled that. This was the only site that I looked at Lightwave T5 Fluorescent Lights - Propagation Lighting

I would imagine that yours would have the 6,500k tubes as I suspect they are closer to sunlight - but I can't be sure. As I say I am not convinced about the different types of light as sunlight seems to do well for both vegetative growth and flowering. Wilkepedia is a bit non committal "Blue spectrum light may trigger a greater vegetative response in plants"

 

I'll confirm they come with the the blue bulbs before ordering, so hopefully it will provide light as shown for 6400K below:



Do you know if these fittings come with any guidance as to how far the should be sited above seeds and plants?

 

You can put them as close as you like. The only reason that lights should not be too close to the plants is because of the heat they generate.

All lighting produces essentially the same amount of heat for the same wattage.This is because most of the power used is wasted as heat - only about 10 % (varies for different types of lighting) goes into light. The advantage of fluorescent lights is that the heat is spread out over a large surface area, so the tube never seems to get hot. This allows you to place plants very close and hence utilise more of the light. Consequently fluorescent tubes are the most economical grow lights.

Fluorescent tubes only consume slightly over 10 watts per foot of tube (irrespective of the tube diameter). This is fundamental to the physics and you can't stray far from this figure. So to have a kilowatt of fluorescent tubes you would need nearly 100 feet of tube. This is not practical in most instances.

So for high power sources you have to use high intensity discharge lamps such as metal halide. These are not usually any more efficient in terms of light produced per watt of power consumed, but you can have a relatively small bulb rated at 400watts or more. Because you have a large amount of power in a small space they get extremely hot and you must have them a considerable distance from the plants. This means that a lot of the light is wasted, making them overall less efficient. But the large power allows a lot of light to reach the base of plants - not just the tops. Consequently these sorts of lights are best for mature plants.

3 or 4 inches is the answer Scrungee - did I get sidetracked. :D

I appreciate the different spectrum you showed. However I think they came from a supplier who is trying to sell special bulbs. The implication from the graphs is that ordinary fluorescents give out less light in total than the other two. I doubt that. I think they give out essentially the same amount of light - its just that the spectral profile is different.

 

Thanks Peter, I think I got the rest. I read that T5 lights don't produce any more light than standard tubes, but use less electricity (I think that consumption bit differs to your comment above) and last longer. I could probably use a basic book on the subject - if only Mr Hessayon had written a 'Growing Under Artificial Lights Expert'.

Next question - do lights need to be on a timer so plants get a natural night/day cycle?


EDIT: Just to expand a bit on why I want the light - so I can bring on seedlings indoors so I can delay putting on the greenhouse heating + get get some extra early season light/growth.

 

Peter I was hoping you would reply to this thread with all your experience on grow lights , and Scrungee thanks for the link to the Jungle seeds . You will have an impressive setup with that Lightwave unit My needs are a lot lot smaller than yours , and it looks like the 15W overhead lamp will be the right size to assist over my prop in a lash up light box.
Just to pick your brains one more time.
Does a grow light help in seed germination ?
Does a grow light help in growing on slow/tricky seedlings to the pricking out stage ?
As Scrungee asked is a 12 hour lighting cycle about right 7 am to 7 pm say ?

TIA

 

Scrungee. Whilst the principle of all fluorescent tubes is basically the same, there are some variations such as better ballasts and better phosphors that will affect performance. Consequently there is some variation in costs and efficiency.

Harry. Most seeds don't need light to germinate (although some like Salvias do), so a grow light won't usually effect germination. But as soon a seed has germinated it will require light.

A seedling will normally grow best if it is outside in late spring on a warm and sunny day. I regard the purpose of a lightbox as a way of reproducing the same conditions inside - ie warmth and a good light level. Using a time switch also copies nature by having an artificial day and night. I use a 14 hour period of light, but I am sure that 12 hours would be just as good. If in doubt try to do what nature would do in say May of June.

As far as difficult seeds go - I am sure that growing outside in May (ie in a light box) would be a help. But it would depend on why they were difficult - could it be acidity of soil or humidity etc. Plants have adapted over millions of years to grow best in their native habitat. So, ideally, we need to reproduce that for them to do well, though many plants are tolerant of quite a wide range of conditions.

Some seeds need special treatment, such as a cold period, before they will germinate. Its not really that they are tricky - its just that we don't always understand how they germinate in their native habitat.

 

I was thinking that using 12 hours/day would enable me to have two trays of seedlings/plants, and swop them over every 12 hours so I get twice the value out of one set of lights.

 

Thanks Peter and Scrungee for your advice , pretty sure now what I need . I will get it set up early Feb to give my Cannas and Chillis a boost . If I don't perceive any improvement keep an eye on Ebay in May for a bargain grow light !:D