HGH Seeds: Follow Along with a Full Optilux Grow



HGH Seeds is based out of Denver, Colorado and creates some of the most sought after genetics in the hemp market today. They are best known for their high CBD/low THC strains for medicinal use. Typically, HGH Seeds grows outdoors, but during the cooler months, they move production indoors, where they grow in large tents. Before, HGH Seeds was growing using 1100 W high pressure sodium (HPS) lamps, and they decided to test URSA’s Optilux light to see how the yields compared. With the new Optilux 640 W LED lights, HGH Seeds used the same strain and growing conditions as the previous setup with HPS lamps. This allows for a direct comparison to be made between the two lighting options.

Here, we follow along as HGS Seeds grows one of their high THC strains using URSA Lighting’s Optilux light. These “follow-alongs” can be very helpful when you want to get ideas and inspiration, or just see how another grower goes from clone to harvest.

Grow Snapshot

Old Lights1100 W high pressure sodium
New LuminairesOptilux 640 W LED
Grow TypeLarge tent with reflective walls
StrainClearwater Kush and Dade County Kush
Hang HeightVariable, 1.7 ft – 2.5 ft
Veg4 weeks, Optilux 640 W, 24 hr day length
Flower9 weeks, Optilux 640 W, 12 hr day length


Veg Week 1 & 2

HGH Seeds chose two strains for this grow: Clearwater Kush and Dade County Kush (Greenpoint Seeds). Clearwater Kush is a unique mix of 92 OG, Chemdawg, and Bubba Diagonal while Dade County Kush has similar origins and is a mix of 92 OG, Chemdawg, and I-95. The clones were moved into a large grow tent with multiple URSA Optilux lights – one light for every 4’ x 4’ area. The plants were grown in soil in plastic trays and were just a couple inches tall. URSA’s Optilux light was kept at a 4’ height above the plant canopy and plants were provided with 24-hour illumination during the veg cycle. By the second week of veg, HGH Seeds transplanted the clones into larger, fabric pots. Fabric pots allow for superb drainage and increased soil aeration. This is an important ecological requirement because cannabis roots are easily attacked by various fungi and do not tolerate standing water well. Under natural conditions, cannabis grows best in sandy and clay-like soil1. These pots will be the final homes for these plants until harvest. The larger pots raised the plants closer to the light source which caused some minor light stress. One sign of light stress is a slight yellowing of the leaves. This issue was solved by backing off the Optilux light by a foot.

Veg Week 3 & 4

By week 3, the plants were looking very healthy and happy. You can see there were multiple Optilux fixtures needed due to the large tent size. This side-by-side deployment works to the benefit of the plant. The Optilux lights are designed to fully illuminate a 4’ x 4’ growing area. When used in series with additional Optilux lights, the light distribution patterns overlap to achieve very uniform light across the entire grow area. At URSA Lighting, we call this “crosshatching”. This ensures that all plants thrive and have similar yields. The URSA Optilux lights are a “full-spectrum” light that delivers high amounts of blue and red light and moderate amounts of other colors of light (violet, green, yellow, and orange). This spectrum satisfies the absorption requirements of photosynthetic pigments such as chlorophylls and carotenoids, which are responsible for converting light energy into carbon for plant growth. Furthermore, the light output (PPFD) of URSA’s Optilux light is approximately 1500 μmol s-1 m-2 at a 2 ft distance from plant canopy to light. This light level has been demonstrated to optimize cannabis photosynthesis rate2.

Flower Week 1 & 2

To initiate flowering, URSA Lighting’s Optilux lights were flipped to a 12-hour photoperiod (day length). Have you ever wondered why a 12-hour photoperiod causes plants to start flowering? Cannabis exhibits a dual response to day length. During the vegetative period (which can last up to 2-3 months), longer days result in more vigorous growth1. To initiate flowering, cultivated cannabis requires shorter days (to simulate the shorter autumn months). Typically, a grower will use a photoperiod of 12-14 hours, depending on the strain. All varieties have a requirement for the minimum number of short days (or, long nights) to induce flowering1. Plants use photoreceptors, such as phytochrome and cryptochromes to measure the duration of darkness. Throughout flowering, cannabis plants require grow lights that produce high amounts of photosynthetically active radiation (PAR). The flowering stage is resource-intensive and many of the processes associated with flowering demand high energy levels. Just like the vegetative stage, photosynthetic pigments must be provided with high amounts of red and blue light and moderate amounts of green, yellow, and orange light. Since the plant canopy is getting rather dense, soon the plants will need to be “scrogged”.

Flower Week 3 & 4

On week 3, the ScrOG net was added to ensure ample light penetration to the lower leaves of the plants. The lower level of the plant canopy is known as the “intercanopy”. While we refer to light hitting the tops of the plants as the PPFD, light that reaches the intercanopy is known as the PPFDi. PPFDi is dependent on the amount of light at the top of the canopy, leaf density, and optical properties of the leaves. It’s important that enough light reaches the lower canopy, because these leaves are still capable of performing photosynthesis and contributing energy to the plant. It’s also important to choose a horticultural light delivers a sufficient amount of green light to the plants. Green light is easily transmitted through plant leaves, so it’s great for providing light to the lower levels of the canopy.

At week 4, we start to see an elongation of the female flowers and the leaves are filling out a bit more. We can also spot the first white pistils growing out of the flowers. These fine white hairs function in capturing pollen from the male flowers and facilitating pollination of the flower. Of course, there are no male plants in this tent, so these pistils will slowly lose their white coloration and progressively dry out and darken to a yellow, orange, red, and brown color over the course of flowering.

Flower Week 5 & 6

We are now about half-way through the flowering period. The floral meristem is no longer growing, so the plants have nearly reached their full height. The flowers now begin to increase in weight and density as they mature along the main flowering stem. Additional inflorescences (flower bunches) are cropping up around the main flowering stem. Simultaneously, dense trichomes are developing on the flowers and leaves of the main flowering stem.

It’s week 6 and the plants are still looking great. At this point, you can start to make out some minor phenotypic variations. The plants also appear to be growing ahead of schedule, but it’s difficult to confirm at this stage. During the flowering stage, it’s important that heat levels are managed properly. The reproductive tissues (the flowers) are more sensitive to heat than the vegetative tissues (leaves). Since we are using an LED light, it’s easy to manage these heat levels using 2 small fans – one for bringing the cool air in and one for pumping the warm air out. At this stage of the grow, HGH Seeds prefers to keep their temperatures around 74°F with lower and upper limits of 70°F and 76°F.

Flower Week 7 & 8

The flowers are really starting to gain some volume. Between week 5 and week 8 is when the greatest increase in trichome number is observed3. It is during this stage that a grower could alter environmental conditions to manipulate trichome size and number. Trichomes are hair-like outgrowths found on the epidermis (skin) of cannabis flowers and leaves. Trichomes are where cannabinoids and terpenes accumulate. High light intensity is one method of increasing trichome size or number. The Optilux light is particularly good for this purpose because it provides plants with a very high light intensity.

We’re nearing the end of the flowering period. The flowers are continuing to become denser; the pistils are drying out and are darkening to a yellow-orange color. It’s at this time that a grower must start paying particularly close attention to the trichomes. Glandular trichomes can be divided into two secretory phases: mature and aged. Mature trichomes are translucent in appearance and are most active in secretion4. Aged trichomes are yellow/brown and senescent4. Mature glands are known to possess the highest content of the major cannabinoids4.

Flower Week 9

We’re in the last week of flowering, and these plants will be harvested in the next few days. The leaves are beginning to dry up and lose their bright chlorophyll color. The flowers have completely filled out and are dense, heavy, and covered in sticky trichomes. The heftiness of these flowers can be attributed to a combination of genetics, adequate amounts of light, consistent temperatures, and sufficient airflow.

After harvesting, the plants are weighed and then dried upside down in a controlled humidity room. A final weigh-in of the dry and trimmed buds will be completed. This data is presented below and compared to yields obtained with a 1100 W high pressure sodium lamp.

At the same time, HGH Seeds has already begun a new set of clones under the URSA Optilux lights. Next up – some Gorrilla Glue! Although we won’t be focusing this new grow on our website, you can keep up with it by following @URSA.Grow on Instagram!


Typically, HGH Seeds grows outdoors, where the plants have access to the perfect environmental conditions. However, when winter rolls around, they move production indoors into large grow tents. In the past, HGH Seeds used 1100 W HPS lamps for all of their indoor grows. They were happy with their yields, and were skeptical about whether URSA Lighting’s Optilux 640 W LED lights would be able to match the yields they reached with they tried-and-tested HPS lamps.

HGH Seeds implemented URSA Lighting’s Optilux 640 W LED luminaires for the clone, veg, and flowering stages of growth. For this particular strain, the veg time was 4 week and flowering time was 9 weeks. With URSA Lighting’s Optilux 640 W LEDs, plants receive about 1500 μmol/m2s-1 of photosynthetically active light (PAR) for 12 hours a day during the flowering period! These light levels have been shown to optimize cannabis photosynthesis rates.

With these impressive PAR values, URSA’s Optilux 640 W LED light produced identical yields to the old 1100 W HPS lamps! This translates to a savings of about $500 per year on electricity costs – per 4′ x 8′ tent! That’s a 42% reduction in electricity costs! Furthermore, because URSA’s Optilux light is passively cooled, air temperatures and humidity stayed consistent throughout the grow. There were no massive shifts in temperature when the LED lights turned on and off. The ideal air temperature for cannabis photosynthesis is 25°C (77°F), which allows the plant to convert light into sugars at the fastest rate possible. Because LED lights run cool, HGH seeds was able to maintain this critical temperature throughout the grow. With these conditions, flowers become large, dense, and heavy!

LED lights are anticipated to replace HPS lamps in most applications as a result of their reduced electricity consumption, heat generation, and maintenance costs while delivering an improved quality of light. Cannabis growers stand to greatly decrease their energy use. This directly translates into reduced operational costs for the growers and reduced carbon emissions.

“I am very pleased with the yield because the Optilux LED’s consume about half of the power of the old HPS lamps. With the Optilux at 640 W, we got basically the exact same weight we did from the HPS lights that ran at 1100 watts.

– Scott, grower at HGH Seeds


  1. Clarke, R. C. & Merlin, M. D. Cannabis: Evolution and Ethnobotany.
  2. Chandra, S., Lata, H., Khan, I. A. & ElSohly, M. A. Photosynthetic response of Cannabis sativa L., an important medicinal plant, to elevated levels of CO2. Physiol. Mol. Biol. Plants 17, 291–295 (2011).
  3. Happyana, N. & Kayser, O. Monitoring Metabolite Profiles of Cannabis sativa L. Trichomes during Flowering Period Using1H NMR-Based Metabolomics and Real-Time PCR. Planta Med. 82, 1217–1223 (2016).
  4. Mahlberg, P. & Kim, E. Accumulation of cannabinoids in glandular trichomes of Cannabis (Cannabaceae). J. Ind. Hemp 9, 15–36 (2004).

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optilux 640watt grow light

Optilux 640 W

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