Table of Contents:
- How to Grow Cannabis 101: An Introduction to Cultivation
- Cannabis Greenhouse vs. Indoor Grow
- Minimizing Indoor Grow Costs
- How to Maximize Cannabis Yields
- Cannabis Greenhouse Construction Process
- Cannabis Cultivation Equipment
- Planning a Cannabis Cultivation Facility
- The Unique Challenges of Cannabis Cultivation
- VPD Dehumidification & Cannabis Cultivation
- Light and PAR
- Cannabis Irrigation
- Top 20 Cannabis Growing Questions – FAQ
- Glossary of Terms: Cannabis and Hemp Extraction
- Industry Resources
Top 20 Cannabis Growing Questions – FAQ
Answers to Frequently Asked Questions about Cannabis Cultivation
Got a question about growing cannabis? Which grow method is better, indoor grow, hybrid, old school greenhouse or sun grown? What equipment is most vital to a successful grow operation? The answer may be here! The following are the top questions that our in-house cannabis cultivation experts are asked on a regular basis.
1. Should I grow my cannabis or hemp in an indoor grow, outdoor sun grown, or hybrid greenhouse?
The answer to this question is “it depends”. In that, it depends on so many other factors but the most important factor is the answer to yet another question:
- What’s your end-product?
If you start with the end result that you’re seeking the answer will reveal itself. For example:
- If you’re growing industrial hemp for fiber on a large scale, you’ll probably want to go for either open-air, sun grown or large-scale greenhouse
- If you’re seeking to produce high-potency THC cannabis, then a fully enclosed indoor-grow may be ideal
- If you’re wanting to reduce electrical costs and grow craft-style cannabis strains with an emphasis on terpene-rich flavors, you may consider a hybrid indoor grow/greenhouse facility with shade systems to make the most of natural sunlight
2. Should I grow cannabis from seed or clones?
Cannabis or hemp plants can be grown from either seed or clones.
Clones are produced by taking a cutting from a mother plant and allowing it to grow roots resulting in genetically identical, all-female plants with vigor and predictable traits.
In comparison, feminized seeds may be less expensive than clones but have a greater chance of producing male and/or hermaphroditic plants. This means that hemp grown from feminized seed needs careful inspection to remove any male plants, increasing the cost of labor and production.
Both feminized seed and female clones have advantages and disadvantages that should be considered before investing in either.
3. How much pesticide do I need for my cannabis plants?
Ideally, you want to reduce the need for pesticides by taking precautions to prevent any insect penetration into your crop to begin with. But if you do get an infestation, there are several steps you can take.
With an indoor grow or greenhouse hybrid facility, you can take the following steps:
- Ensure all windows, roof vents, or external door openings are covered with insect screens
- Use a HEPA intake filter on all HVAC ducting
- Include a ‘decontamination zone’ at the entryway of your greenhouse or indoor grow
- Use peer reviewed and approved organic pest control sprays
- Place a physical barrier over your grow medium, for example a two-inch layer of sand, perlite, or other similar product to prevent insects from laying eggs in the soil to end their life cycle
4. How much fertilizer do I need for my cannabis plants?
The amount of fertilizer you’ll need will depend on the growth stage of your cannabis or hemp plant.
Seedling or Cutting Stage: Use minimal or zero fertilizer during the seedling stage. Rooted cuttings are often deficient in nutrients. Feed both cuttings and seedlings very gently with a 1-1-1 balanced formula at about 100 ppm for each once there is adequate root development.
Vegetative Stage: During the vegetative stage, the plant will require a base nutrient that is higher in nitrogen and lower in phosphorus and potassium. N-P-K where the number in the N position is higher than the others (i.e. 12-6-6).
Flowering or Budding Stage: Flowering cannabis plants need more potassium (and less nitrogen) to promote the growth of the desired big sticky buds or resinous flowers. During the first two weeks of flowering, most growers feed their plants with a 5:7:10 fertilizer.
5. How much light do I need for my cannabis plants?
There’s no definitive answer to how much light your plants need because plants need different amounts of light during each growth stage. However, there are some general guidelines as to how much light they will need in each stage. Cannabis plants have four roughly distinct growth stages:
1. Germination stage (seeds sprout at 3-10 days)
- Keep in a cool dark place away from direct sunlight or artificial light
2. Seedling stage (seedling grows at 2-3 weeks)
- 16~ hours of light a day (indoors)
3. Vegetative Stage (seedling grows at 3-12 weeks)
- 12-18 hours of light a day (indoors)
4. Flowering (buds/flowers through to harvest at 8-16 weeks)
- 12 hours of light and 12 hours of uninterrupted dark each day
6. What kind of growing medium should I use for my cannabis plants?
You can grow cannabis or hemp plants in a variety of mediums:
- Soil/Compost: the simplest and traditional way to grow your plants, this method delivers high-quality and high-taste end products. It may not deliver the highest yields but a more natural terpene-rich high
- Coco/Perlite: A mix of coco and perlite delivers the benefits of a hydroponic grow with the ease of a soil grow. But you will have to closely watch your pH levels because it’s less forgiving of mistakes than soil
- Rockwool: is an inert rock material that appears similar to wool. It’s made from basalt rock and has excellent water-retention abilities
- Hydroponics: plants grow in a small amount of rockwool with roots reaching down into a liquid solution of water and nutrients
- No medium at all: plants are suspended above a liquid nutrient solution
7. What yield and CBD/THC ratio might I expect from my plants?
This is the big question and once again, it all depends.
For an example, we can look into UDAF records, there were over 3M hemp plants grown in Utah in 2019 when hemp was first legalized. An estimated 800,000 pounds of biomass was harvested that year. The “dry flower” yield ranged from 0.75 to 1.5 pounds per plant.
State tests measured an average CBD content of 5.3% with an average THC content of 0.28%. This means the average CBD/THC ratio was about 20 to 1. Most varieties that have been studied in controlled environments have a similar ratio.
8. How do I sell my hemp or cannabis for processing?
If you’re not running a fully verticalized operation you’ll need to source a processor to buy your plants. Ideally, organize a buyer before you start planting. This should be obvious but is often forgotten in the excitement to grow your favorite strain. It pays to do your research and find out the answers to questions like:
- Which strains are in demand in today’s and tomorrow’s market?
- Is there someone located nearby who I can sell my biomass to? (You don’t want to have to transport your biomass across state lines for example, because in the US this is still illegal, even from one legalized state to another!)
- Can you set up the terms of the sale before you even begin planting?
9. Why is it so important to choose female plants above male plants?
Female hemp and cannabis plants are preferred in the industry because male plants produce pollen that fertilizes female plants which causes seed production. This stage of plant development reduces the number and density of flowers and therefore cannabinoid production—the highly sought after THC and CBD-rich oil.
Also, keeping female plants in a state of ‘frustration’ away from male plants helps encourages them to produce more of the famous sticky, trichome-rich buds (flowers).
10. How and when can I detect plant gender?
Both male and female plants can be identified at the pre-flowering stage.
Female flowers have two white hair-like structures protruding from them which very obviously differentiates them from males early on. In comparison, male flowers are round, lack the white hairs, and typically occur in dense clusters.
Male plants will produce pollen for a span of two to four weeks. If a male plant is spotted in your crop it needs to be removed and destroyed immediately to prevent pollination of the females.
11. How long should my cannabis plants germinate and propagate?
If you have prepared your grow medium correctly and your seeds are in a cool dark place, you should see tiny stems sprouting from the soil within 4-7 days. When the stems of the seedlings reach 2-4 inches, they need to be transplanted into larger pots so that the roots have room to spread out and down.
12. When should I switch my cannabis plants from the vegetative growth stage to the flowering stage?
When your cannabis plant has moved from germination to propagation, this is considered the beginning of its vegetative growth stage. In this stage, it’s important the plant focuses on developing healthy stems, leaves, and roots. Plants should be kept in their vegetative stage for about 60 days to give the plant ample time to focus on storing energy to promote maximum yields, and to acclimatize to its growing conditions. After these 60 days, the plant should have considerable shoots and roots systems, and is now ready to be switched to its budding/flowering stage.
13. Does frost affect CBD, CBG, or THC levels?
Surprisingly, unlike most cultivated plants, hemp and cannabis withstand mild frost quite well. A study at the University of Vermont in 2018 tracked the difference in temperatures and resulting CBD levels of hemp plants. They discovered that though uncovered hemp plants experienced below-freezing temperatures several times throughout the study, the overall CBD concentration was unaffected. They also found that frost and cold weather can cause the plants to change color, but this has little to no impact on CBD or THC levels (Darby, 2019).
14. What should my target pH and EC be?
Cannabis and hemp does best in soils with a pH ranging from about 6.0–7.0.
The perfect EC level for cannabis or hemp plants is around 0.5-0.8 until about 13-16 days post-germination. This number should be progressively increased to 1.1 towards the end of the growth period.
During flowering stage, plants need more nutrients so your EC should be between 1.2 and 1.5, and maintaining it there until the fattening period, where it should be increased to 1.8 / 2.1. Any higher EC levels than 2.5 are known to reduce crop yield.
15. How do I mitigate odor when growing cannabis?
Odor mitigation is a critical factor when it comes to growing cannabis or hemp indoors in a greenhouse or an indoor grow facility. Not only will you foster positive relations with your neighbors but you’ll also enhance the security of your facility. There are several things you can do to reduce the odor inside and outside your facility:
- Use a carbon filter to literally ‘scrub’ plant smells out of the air before it’s extracted into the surrounding area. Carbon filters should be part of every ventilation system.
- Ventilation: draw in 20% less air than you extract to maintain negative pressure.
- Ozone generators can also be used to remove odors via oxidation.
- ONA blocks, gels, and sprays are the best odor neutralizers to use outside your growing area.
- When your plants are flowering keep a close eye on heat and humidity to reduce the release of odors.
16. What is the ideal relative humidity for cannabis plants?
The recommended relative humidity (RH) for a flowering cannabis plant is 40-50%. Moisture is reduced to this level mainly to prevent the growth of mold that the plant is very vulnerable to at this stage. Learn more about relative humidity here.
17. How do I know when my plants are ready for harvest?
The best way to tell if your cannabis or hemp plants are ready to harvest (both indoors and outdoors grows), is to inspect their stigma, the hair-like strands that cover buds. These hairs will turn from white to orange and begin to curl. Additionally, the trichomes (the resinous glands) will turn from clear to opaque, then amber in color.
Waiting to harvest until approximately 70% of trichomes have turned amber is ideal to ensure a higher concentration of CBD and THC (cannabinoids).
18. What is the best harvesting method?
Hand harvesting of THC- and CBD-rich cannabis is the tried and true method that has been used for thousands of years. Ideal for both indoor grows, greenhouses, and hybrid facilities, hand-harvesting is still the ideal method for most growers even though it is labor-intensive.
Modern machine harvesting is only viable in large-scale, outdoor sun-grown of hemp crops. The typical method used is straight combining where the combine header is lifted to cut the crop just below the seed head, which typically is the top one-third of the plant (top 60 to 90 cm or 23 to 35 in.).
19. What is VPD when growing cannabis?
Vapor pressure deficit (VPD) is a measurement of the difference between the moisture (water) in the air versus how much water the air can hold in total.
When your goal is to produce a quality cannabis crop, VPD dehumidification is a critical factor in your growing SOP (standard operating procedure) because it’s essentially the shortcut to ensuring your cannabis will grow at just the right humidity levels. Learn more about VPD here.
20. What is the most important piece of equipment that I need in my indoor grow space?
The most important piece of equipment you’ll need in your indoor grow or greenhouse facility is environmental controls automation equipment. This is because automation ties all the various systems (irrigation, cooling, heating, ventilation, etc.) together to ensure that they all run smoothly and with the least amount of human intervention.