Grow Light germination ?

Thats fine then, it is supported by "other" means

Not the prime walnut dining table I hope

Jack McH

 

Yes - with it indoors in my study and an enclosed box around them I have to keep my heated propagator on a minimum setting. I've got an electric storage heater in that room and I'm trying to coordinate the coldest time of day with the 'lights off time' to replicate a natural growing enviroment.

 

I wouldn't have thought that they give out that much heat. They are quoted at 96 watts - of which about 10% will be given out as light and the rest as heat.

That wattage is very similar to my lightbox. However, my lights are attached to a suspended ceiling in the box, with a small air gap all round between the ceiling and the walls so the hot air can escape. I did this intentionally to prevent the build up of heat, as I wanted to be able to go away for 10 days and leave it on without the fear of it bursting into flames. Consequently I use a heated propagator inside the box. But that is only 28 watts (for a double seed tray propagator) compared to the 90 odd watts from the lights.

So if you have no air gap, you will probably get a fair build up of heat. I would suggest that you leave space for a propagator and then use a thermometer to see if its needed. Of course, it also depends on how warm the room is. My room rarely gets above 60F. If yours is 10F hotter then your seeds will be 10F hotter.

 

An adjustable vent(s) is my next planned addition, so I can either have a heated propagator inside & adjust the vent(s) or have the propagator outside with seeds germinating in it, and plants in trays/pots inside the light box benefitting from the warmth of the lights. I have wondered about fitting a small (CPU?) fan.

 

As heat rises I would have thought a hole near the top would be cheaper to run. :D

 

I have a few thoughts on this. I'm in the Metal Halide camp, rather than the fluorescent tubes camp as my need is as much overwintering plants that are taller than seedlings, although I also use my lamps to bring on seedlings in the Spring (the taller plants take their chances in the conservatory when the seedlings need the lamps - the light levels are OK from end February onwards for the plants I am overwintering), and once the seed-sowing bonanza is drawing to a close I prefer to use the lamps [during the night] as a boost to hurry-up Tomato plants etc relative to ones just raised in natural light.

Can't rememebr the specifics, but I took Shiney some Tomato plants last year that were sown around the same time as his, but mine under lights were a lot bigger and started cropping earlier. The seedlings / young plants didn't get any extra heat, although I did maintain minimums of 10C (by bringing them in from conservatory on cold nights)

Most of my research was done on the Cannabis forums, they are a wealth of information, and I bought from 3C Hydroponics (who have stores around the country).

Type of Lamps

Metal Halide (and its discharge-lamp cousin High Pressure Sodium) has greater canopy penetration than Fluorescent (just as well as MH generates a lot more heat !), so Fluorescent must be as close as possible (check heat on the back of your hand over quite a decent period - a minute or two); Fluorescent will be safe within a couple of inches whereas MH will need 18" or more.

When Fluorescents are that close to the plants the amount of light they can throw sideways is limited, so you have to have rows of tubes close to each other - and also to get a decent amount of light output. The consequence of that is that they only cover an area about equal to the area of the tube-assembly itself. So a 2' x 2' array of tubes is only going to give you a 2' x 2' "growing area", whereas a MH lamp of, say, 600W will cover nearly 4 sq.m. of growing area.

So for seed germination Fluorescents are good, but do make sure they are only a couple of inches above the plants. This is harder as the plants grow (assuming a mixture of different height plants). You can prop the shorter ones up on upturned pots etc. but if you have a heat mat that will move them off the heat of the mat.

An alternative to Fluorescent tubes is a CFL - looks like a revolver of short Fluorescent tubes! and fits into a reflector more like an MH bulb.



Forget about LEDs, they output so little light and, currently, cost so much that they aren't cost effective - unless you have a real problem getting rid of the excess heat. At some future time they will offer good light per watt, thus low heat output, and will probably be tailored to exactly the wavelengths the plants need thus less energy wasted on wavelengths that the plants can't then convert, so when the price of LEDs comes down they may be just-the-thing.

Moving the Light Rig / Adjusting Height

You can use chains to make the lighting rig easily adjustable, or friction-rollers (which is what I use) - e.g. Easy Rolls:


Timers[/SIZE]

My lamps run on a timer to come on during the night with Economy-7. I don't know whether plants need a dark-period, or if so for how long etc. I figured 7 hours was enough, and my electricity is substantially cheaper at night

However, there is an issue around timers. A standard timer won't take the load the ballasts of these lamps draw during initial startup (and possibly as they "pulse" too? although I don't know that for sure), so in order to sue a timer you need a "contactor" - this works by you providing a conventional mains timer which provides power to the contactor and the contactor (I suppose the contactor is a a solenoid?, or a "contactor" might be a different animal that does a similar job) then delivers the power to the lamps - so the timer runs at low wattage. I guess a decent timer will take a load of 4 AMPs??, however I don't know what the startup load of lighting ballasts is - i.e. what total Fluorescent tube wattage / tube numbers you need before it becomes an issue.

Reflectors

Don't skimp on the reflector above the bulb. You want to reflect as much light downwards as possible.

In terms of the "walls" there are options.

From the research I did the best reflective material is Mylar.

Kitchen Aluminium Foil is actually very poor - which I found rather annoying!! as I used to use that to line half-a-cardboard-box that I put room-side of my windowsill seedlings to stop them getting drawn to the light ... actually it turns out that Tin Foil is a very poor choice for a light reflector :(.

White paint is pretty good, and a convenient material.

Polystyrene is actually a close second to Mylar (which surprised me given its rather matt and uneven surface), and has the added benefit of insulation - so you can perhaps insulate-in some of the heat from your lamps as an extra benefit. Perhaps no wonder that it is used for ceiling tiles on suspended ceilings in offices to reflect more light downwards

Heat Output

An MH lamp generates a lot of heat, fluorescent lamps less so. However, in my case I only use it in Winter, so the excess heat just goes into the house and reduces the central heating commensurately. Of course using electricity to heat the house, via lamps!, is not as economic as a central heating boiler, but its not a total loss either, so don't write off the total cost of running the lamps if you use them during Winter (or, use that as a justification to your dearly beloved partner!)

Cost of Electricity

My yard-stick is that 1 Watt run 24/7/365 is about £1.50. If you have Economy-7 its cheaper for the 7/24ths of that - can't remember the figures, but if 7/24ths is 50% cheaper then that probably makes it about £1.25 for 1 Watt per year.

So ... if you use your lamp for 1 hour a day for 3 months of the year that would be £0.015625 per watt per day-hour used
so:
a 100 watt system used for 7 hours a day (over 3 months "growing season") would be about:
0.015625 * 100 watts * 7 hours-per-day = £10.94 for the 3-month season.

Substitute the Wattage of the lights you are planning.

Note that you can put this exact formula into Google and it will calculate it for you:

0.015625 * 100 * 7 =

I don't know how long the lights should run each day. Here's one view that I have read:

"This depends on the type of plant. Foliage plants need about 14-16 hours of light per day. Flowering plants need 12-16 hours of light per day. You should give most plants at least 8 hours of total darkness daily. Try to have the lights on at the same time every day"

Cost of Equipment

One of the issues I encountered with DIY is that if you need a lot of Fluorescent tubes you need a lot of fittings - and the Ballast part of the fittings is not cheap. Although they do last well, and cost of Tubes is quite cheap; although: MH bulbs are also cheap, and both will need replacing long before they wear out as the light-output "power" will tail off. If you happen to have enough "fittings" lying around, or can buy them cheaply, that may be a decision influencing criteria.

No doubt you can shop around / get deals, so this is just the prices from the one web site that I looked at:

4 Tube T5 Light Wave £120 (actually reduced to £95 at present)
6500 Kelvin, 216 Watts, Size H: 6cm W: 38cm L: 119cm, coverage about 1.2 sq.m.

Replacement bulbs £11.50 x 4 = £46.00

8 Tube T5 Light Wave £240 (actually reduced to £156 at present)
6500 Kelvin, 432 Watts, Size H: 6cm W: 64cm L: 119cm, coverage about 2.2 sq.m.

Replacement bulbs £11.50 x 8 = £92.00

Ordinary Fluorescent tubes are about 40 Lumens/Watt, CFL and T5 "Full Spectrum" bulbs are about 75 to 90 Lumens/watt. The T5 bulbs are much more efficient and have a better light output spectrum for plants than their T12 predecessors, but T12 may be OK for seedlings and low-light plants.


2700-3000 Kelvin bulbs provide higher output in the red spectrum (good for flowering). 5000-6500 Kelvin bulbs are full spectrum with much of the light in the blue spectrum (good for vegetative growth)

Metal Halide (High Pressure Sodium is about the same cost)
Reflector, Ballast, Bulb :
250 Watts = £72.00 (Replacement bulb = £10.00, area = 0.8sq.m, distance bulb-to-plant = 10")
400 Watts = £75.00 (£14.50, 2.3sq.m, 14"-18")
600 Watts = £79.00 (£22.00, 3.9sq.m, 18"-24")
1000 Watts = £153.00 (£57.00, 5.9sq.m, 24"-30")

Double the lamp-to-plant distance for seedlings (but then you cover a bigger area )

Metal Halide outputs about 125 lumens/Watt and is primarily Violet 380-430nm, Blue 430-490nm and Green 490-570nm best suited to vegetative growth

High Pressure Sodium outputs about 140 lumens/Watt and is primarily Yellow 570-590 (nm), Orange 590-630 (nm) and Red 630-750 (nm) best suited to flowering stages

CFL
Reflector and bulb
125 Watts = £47.00 (Replacement bulb £15.00, 0.37 sq.m, 56 lumens/Watt)
250 Watts = £65.00 (Replacement bulb £32.50, 0.58 sq.m, 50 lumens/Watt)

 

Some specific points:

The "blue spectrum" lights emit most/much of their energy in that part of the spectrum (ditto for "Red spectrum lights") which to me means that if that is what the plant needs them what I'm paying for is the energy being converted into what the plant wants / can use, and no sense producing other parts of the spectrum that the plant won't use. The Sun is not on the same agenda, nor budget!, as me.

"Red spectrum" is better for flowering ... if you are growing Chrysanthemums, or Canna-something-or-other !

T5 lights produce MORE light than the old Standard Tubes (the old T12 type)

The "last longer" bit is probably irrelevant. The light quality will tail-off with age, so you would be advised to replace them after N-hours (or possible N-months regardless of actual usage), rather than waiting until they fail. They'll probably run for another Nx2 hours in the kitchen thereafter though !!

I doubt that will help, seedlings likely to become leggy.

"Does a grow light help in seed germination ?"

Maybe. Some seeds do need light to germinate (so be careful not to "bury" them, or cover them lightly with Vermiculite which is fairly transparent)

"Does a grow light help in growing on slow/tricky seedlings to the pricking out stage ?"

Speeds the process up, and will create more stocky seedlings. I have some still in the quarter sized seed tray that were supposedly tricky (Plumeria cerise) so I started them off early, they germinated a month of more ago (which I wasn't expecting!) and have been under my strong MH light and have hardly grown at all, so I have not had to prick them out yet - as I don't have the space for them in individual pots for another month. They look lovely and green and really stocky though so should make good plants

"As Scrungee asked is a 12 hour lighting cycle about right 7 am to 7 pm say ?"

If you have Economy-7 do them during that interval - cheaper But if you want two batches that you swap over IME 12 hours will be enough (provided the lights are strong enough - maybe over-spec that part to make sure, rather than having "weaker" lights on for 14 - 16 hours and losing the opportunity of two-batches ?

Definitely, although it may be overkill. White paint is better than one might think, and polystyrene is somewhere between the two (and also insulates). I'll try to find a reference to this.

"I've got some thin expanded polystyrene for cutting up and putting under trays/pots with seeds that don't require so much heat as other seeds so they can all go in the propagator together."

I think the polystyrene will restrict the heat too much, and you risk that the element under it overheats ? Are the seeds going to mind that extra warmth?

John: might be worth considering a reptile heating mat, they are cheap-as-chips compared to horticultural heating mats. It would be wise to have a decent thermostat though, it won't be hard to save enough energy to pay for the thermostat.

Jungle Seeds do some mats - Bio Green or somesuch brand name. Watch out for the ones that include semi-rigid-coil thermostats as they aren't intended to be bent about much, and getting them in-and-out each season is highly likely to damage them (there's an article about it somewhere on the internet along the lines of "I wouldn't have expected this for a German-engineered product")

 

Welcome back Kristen, I trust your keeping well?

Steve...

 

Misread that as "I trust you are sleeping well" !!!

 

Welcome back kristen - It will take me three days to read your post and absorb it ! I am building a mini light box , which can go in the corner of my study and then pack away in 10 minutes - in April. More details to come...

 

I was using foil blankets as well to cover my tubular frame , surely they will be OK I really dont want a polysterene box in the corner of my little study. All the cannabis grower videos seem to use reflective foil .

 

Its fascinating to read the Cannabis Forums. The intricate details they go into to squeeze the last ounce out of their plants (I personally have NO idea if that much effort is justified in the final product ... but then I don't really understand why people get besotted by Chillies (I grow them for the kitchen - means-to-an-end for me) of Palms (look right-out-of-place in the UK to me) - but I'm clearly a Heathen in such matters ...

Reflectivity figures from a hopefully representative site:

Black Less than 10%
Aluminium Foil 55-70% - seeing that now annoys me, I used that for YEARS !!!
Semi-gloss White Paint 60-70%
White / Black / White Film 70-85%
Flat White Paint 75-80%
Polystyrene Foam Sheeting 75-85%
Mylar Sheeting 90-92%

So if you are going to use white paint it looks like you need Matt rather than Gloss ...

 

Reminds me of the postcards I used to send to my mates from holidays abroad:

"I'm writing this slowly because I know you can't read very quickly ..."