The GLR Technique

The Gas Lantern Routine Technique (GLR technique) is a lighting system that will allow you to save a lot on electricity bills as well as bulbs and overall spending on your crop without risking quality, flavor and effect. Reinhard Delp is a cannabis visionary that brought the GLR technique back to life. For indoor grows, during the veg phase almost everyone tends to grow under 18h of light and 6h of darkness, although this may vary as some people do 16/10, others use 20/4 and some even grow in 24h of constant light.

Reinhard Delp is a true cannabis visionary, having invented the patent for ice-water extraction. He also shared his peculiar growing method, the GLR technique, which allowed him to save on electricity bills without putting his plants in danger. Plants absorb photons during the day, which they then synthesize into sugars and nutrients at night by using the energy they’ve stored during the day. Standard light periods are 18/6 and 20/4, and these tend to give the best results when growing indoors with a veg period of around 3 weeks and a flowering period set at 12/12, which would flower your plants between 8 to 12 weeks. These cycles, of course, don’t imitate a natural light cycle at all, but they seem to give the best results indoors.

People that tend to use straight up 24h of light get the results they’re looking for, which is a much faster growth than with other light schedules thanks to how the sugar and nutrient synthesis is much faster due to how many hours of light are being absorbed. Thanks to this high quantity of photons they can easily synthesize the nutrients, however this amount of light can stress the plant to the point where it might become autoflowering or completely flower with 16h of light.

Cannabis flowering is due to the production of a hormone called florigen which regulates the entire principle of flowering and it is produced under 12h of darkness. This means that in fewer than 12h of darkness, cannabis plants shouldn’t flower, so Delp’s technique is perfect so that your plants don’t ever flower, and it can be used to maintain mother plants without using too much electricity or generating too much heat. His technique is comprised of 12 hours of light, 5.5h of darkness, one more hour of light, and 5.5 more hours of darkness. This means that your plants will never have 12 full hours of darkness, so they won’t automatically begin flowering and you get to save 7 hours of light a day, which translates to around 175 hours of light during the growth phase which can also make for quite a big save on your electricity bill.

Keep in mind that some people begin their seeds off at 12/12, meaning that as soon as plants reach sexual maturity they begin flowering, which tends to happen around the 12st day of life depending on the strain. This light cycle is generaly recommended for those growing Sativa strains; the more sativa the strain, the earlier they’ll flower so that they don’t stretch out too much, unless you want to grow in a SCRoG system. This lighting system is also recommended for those who simply want to get their harvest as soon as possible.

The Reinhard Delp light cycle ensures a compact growth in your plants, although theoretically this shouldn’t work but Mother Nature can be quite surprising sometimes. Delp’s technique causes the plants to have smaller spaces between internodes and less chance of stretching out too much. Growth tends to be a bit slower when using this technique. It might be better for sativa strains due to how tall they tend to grow indoors. It’s true that indica strains will lose somewhat in production as they have a slower growth rhythm than sativa plants.

After the growth phase it’s time to begin flowering your plants, and this phase is generally directed towards saving energy; you won’t have to use 12 hours of light. During the first two weeks of your seed you should have it at 16h, unless you want a faster growth in which case you can place it at the 12/1 technique straight away until you reach the flowering phase, where the hours of light will be even more reduced, from 12/1 to just 12. Online you can find some obscure advice on the Delp technique which instructs us to use 11/13h cycles with 11 hours of light and 13 of darkness and reduce the light a half an hour every two weeks. There are Canadian growers that do completely opposite growth cycles than us, using 6 hours of light and 18 of darkness. This kind of cycle might imitate the outside climate a bit better but we severely doubt that it gives them decent results.

Another piece of advice often used is that regarding growing mother plants and clones in this cycle; all you need to do use raise the “florigin annulment” period by a half an hour; Delp recommends 12 hours of light, 5 and a half of darkness and one hour of light, however in the case of mother plants and clones you can increase light exposure a bit, say about 12/4/2/4. This will ensure your plants get more light.

The biggest differences found in this technique are a lower yield due to the reduced light exposition for the plants. However, it also makes for an incredibly big saving on electricity bills, as well as other products like water and nutrients, and our precious time of course. This technique, just like any other, has both pros and contras, and depending on your needs this technique might be the right one for you.

Author: Fabio Inga
Translator: Ciara Murphy