Best Grow Lighting for Medical Cannabis Cultivation

The type of cannabis grow lighting used depends on the size of the growing room as well as the technique used

Indoor cannabis cultivation generally requires the light intensity to be between 2000 and 3000 lumens per square foot for good yields. Tungsten filament bulbs are quite inefficient and produce much more heat than light. There is certainly a great deal of debate about the relative merits of several varieties: fluorescent tubes, mercury vapour, metal halide(MH) and higher pressure sodium (HPS) and nowadays it is common to see CFL bulbs, basically energy-saving bulbs.

Generally, mercury vapour and MH are beneficial through the vegetative progress stage and HPS are best for flowering and ‘acceptable’ for the veg stage. CFLs and fluorescent tubes are for general purposes. Nowadays some HPS bulbs are being made and sold with ‘dual spectrum’ meaning they have enough of the blue and red bands of light to see your plants through both stages of development and that is what we use ourselves in the main.

Fluorescent Grow Lights

Fluorescent tubes and their fittings are obtainable in an array of lengths. Longer tubes obviously emit a lot more light than short ones. Normal 1″ diameter halo phosphate tubes are rated at about 30 watts each metre and output about 2,500 lumens each metre (and 85 lumens each watt). Tubes are offered in an array of colour temperatures: 6000K (daylight), 4000K (awesome white), 3500K (white) and 3000K (warm white). Daylight tubes have a lot more blue in their spectrum and warm white much more red. Results usually are not a lot distinct whatever tubes you use but, for those who have the option, either use a mix of warm white and awesome white or adjust from awesome to warm white when the flowering stage starts. A quick calculation reveals that to accomplish 2000 lumens for each square foot you must virtually cover the whole area in the room’s ceiling with fittings. The fittings can get pretty hot, so enable a space among them for air to circulate well.

The light intensity drops really dramatically as you move away from your tube; intensity at two feet distance is only a quarter the intensity at 1 foot! This means that cannabis plants’ progress is only truly luxuriant up to a number of feet through the tube. Fix the tube fittings to a board which can be attached by cords or chains for the ceiling; this way the tubes might be kept as close as feasible (a couple of inches) towards the top from the plants. The board will have for being moved daily when the plants are developing effectively.

Fluorescents are most valuable in situations where you usually are not developing the plants quite tall. For instance, being a light source for cuttings or for the “sea of green” approach.

CFL Grow Lights

Often called “energy-saving bulbs” CFLs use low wattage, put out little heat and are easy to find. They are not as efficient as HPS/MH but are better than traditional “tube” fluorescents and you can get a decent yield from them if you use enough!

Here’s a pretty easy way to figure out the bare minimum in CFLs for your growth–start to finish…. (Thanks to Lady Zanadra for these CFL pointers)

Never use any output smaller than 100w, it’s a waste of money and inefficient.

For babies: sprouts to 3 leafers, use 2 bulbs for up to 6 sprouts
3 leafers till 10-12 inches–1 bulb per plant
10-12 inches till they go 12/12– 2 bulbs per plant
12/12 till harvest– 3 bulbs per plant, additional side/back lighting helpful.

OR get the BIG CFLs That are 100-150w usage 500-600w output in a decent reflector (These do NOT fit in a household or regular fixtures! You MUST get the special ones made just for them.) and use 1 for every 2 – 3 cannabis plants.

HPS Grow Lights

HPS bulbs are generally available from 150W up to 1000w sizes. The most common sizes used in indoor cannabis cultivation are 250w, 400w and 600w. This amounts to lumens between 100 and 150 lumens or so each watt, according towards the size of the lamp. Their colour temperature is pretty low, between 2000K and 3000K; they emit a pinkish, golden white light which can be similar to autumn daylight. Remember tho, HPS bulbs are now also being made with ‘dual spectrum’ meaning they have enough of the blue and red bands of light to see your cannabis plants through both stages of development.

You will find many benefits to HPS bulbs:

The efficiency, in terms of lumens for each watt, is higher.
There’s usable light at a greater distance through the bulb, compared with fluorescent tubes.
In most domestic installations, you can find only one particular or two bulbs to adjust as opposed to maybe twelve or far more fluorescent tubes.
bulbs possess a long lifetime of 20,000 several hours or much more (despite the fact that the output drops, gradually, throughout the life of the lamp – it’s greatest to adjust them after a single year’s use)

The disadvantages are:

The price of a whole program comprising handle gear, lamp and reflector may run into a couple of hundred Euros.
HPS bulbs should usually be kept at least 18″ above the plants to prevent leaf scorch or even fire!
Water must be kept properly away from the bulbs as they can explode if splashed.

LED

In an ideal world, only if you have a very small space would I recommend anything other than HPS. With the newer HPS bulbs being offered with the dual spectrum range then it is going to make sense in most cases. Initially, there will be a slightly higher outlay but you will be rewarded threefold in so many different areas.

However, naturally, I am aware of the energy costs and the recent crisis we had after the war in Ukraine started emphasised this big-time. , It is only sensible that I keep testing LED lights and next season I hope to do even  more hands-on testing, as we tend to do with most technology tbh

I have been given, shown and educated about LED for over a decade, we use them in greenhouses to prevent light deprivation and to keep down costs.

I simply don’t think the savings outweigh the benefits of hps still for most small home-growing projects. Even with my consultancy fees for a new grower of about 300 euros over the course of an entire grow,  and you chuck on 100 euros per month for hps power you’re still going to be producing the finest quality cannabis for under 2 euros per gramme.

Conclusion

The following pages show the type of bulb I would be happy to use, they include my trusted Amazon affiliate code meaning I might earn a few bob on commission.

Sylvania Grolux 400w HPS
Sylvania Grolux 600w HPS

I’ve also been very happy with the Philips Sumaster Dual Spectrum bulbs if you can see them.

Of course, you can also nip over to our patners and heklp yourself to 5% discount using my code Paz67. Growshop

 

 

For now, here’s a specific article on LED lighting for cannabis that I began working on with regard to expanding that section somewhat, I have been testing products from 350 watts up to 750 watts for the last 2 years with clients and at home, despite I find it difficult at home to be regimented as I do ‘at work’  I like to have manual work and put plants outdoors manually whenever I can at home and being in Spain that’s pretty much a good 8 hours a day of power saving over the year.

Most of the inexperienced growers that approach me in he last few years bought into LED with mixed results. Some carry on, some convert back to HPS. As always, it depends sn your individual circumstances as to what might be best.