Happy Independence Day.

The Denver Post has been running some good stuff on the pot biz in Colorado.

Want to grow your own weed at home? Some basics

So you want to grow pot. Or you’re worried the neighbors will.

Marijuana is the botanical conversation piece that just won’t go away. Reactions to it run a wild gamut: It’s the evil weed or a source of future state tax revenue and entrepreneurial ingenuity. Or it’s the only path left to freedom from pain for some people, and journalists should write about it with the same seriousness that they accord blood-pressure medicine.

If you’re 21 or older, Amendment 64 allows you to cultivate up to six marijuana plants in an “enclosed, locked space” in Colorado. (This is still illegal under federal law.)

UPDATE: Governor’s pot panel recommends allowing only indoor growing

Sounds simple. But growing marijuana isn’t easy, those who do it professionally say.

Growing cannabis from seed is possible but impractical.

Such activities are subject to federal prosecution.

One thing is certain: Legalization is changing the landscape of our state. Maybe not our yards, but surely our headspace, our parties, our neighborhoods and our lives. If we understand the plant, it will help us talk about that change using facts rather than fear or naive enthusiasm.

We went to experts with the questions we felt any gardener and homeowner would have. Our interviewees for this story and video were Kayvan Khalatbari and Nick Hice, co-owners of Denver Relief, a medicinal-marijuana dispensary whose growing facility is home to about 1,900 marijuana plants.

An overview of the basics

Question: Where can Coloradans grow marijuana plants? Can people just stick them in a sunny window next to basil and aloe?

Answer: A big thing to remember with marijuana plants is that they need to flower to produce THC ( tetrahydrocannabinol, the chemical that gets people high) and other medicinal cannabinoids. In order to do that, they need 12 hours of light and 12 hours of total darkness a day.

So the best place to grow marijuana is in a room in the basement with a locked door so light doesn’t inadvertently get in when the plants are “sleeping.” If you don’t have a basement, a small closet with light-leak protection around the door will work.

Q: Is special growing equipment required?

A: All sorts of prepackaged items are available, like grow boxes or grow tents, that are probably best for a small space like a closet, or fo r someone who doesn’t want to get into growing marijuana too intensely.

But if you’re trying to get six plants to be as robust as possible, you probably need to install something that’s more permanent, like a 400- to 600-watt lamp with a hood assembly that comes with a ballast, which you place at least a forearm’s length above the plants.

Keep in mind that the ballast is going to get very hot, so you need to have adequate cooling in the room as well, like a portable air conditioner with a thermostat. You don’t want the room to get above 80 degrees because the hotter it is, the slower the plants grow. The ideal temperature is 75 to 80 degrees when the lights are on and 68 to 74 degrees when the lights are off.

You also have to watch humidity, because every time you water plants in a small space, you’re going to get high humidity. It should be below 50 percent to prevent bud mold or rot.

You can measure humidity with a hygrometer from a hardware or grow store, and reduce it with a dehumidifier or air conditioner.

Q: How would a home grower comply with the rule that limits them to three plants in flower?

A: That means you can grow only three plants if you don’t have two separate growing areas. The reason having only three plants is bad is that you want to keep a rotation going. Or else every time you get done harvesting, you have to go back to a store. If you want a continual supply, you want the perpetualness of having a vegetative stage and a flowering stage going all the time.

Logistics and costs

Q: How much does all this stuff cost?

A: Most grow boxes are $200 to $400, but if you want one with HVAC temperature-control capabilities, it’s pretty pricey — close to $1,000. You can find grow boxes at most local hydroponic stores or grow shops.

A light system and building materials will run $350 to $1,000, and electricity costs per harvest are $100 to $200.

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The Cannabist is currently accepting marijuana gear for review purposes. Submit your glass, vaporizers, pens and more: cannabistcritics@gmail.com.

Q: Where would a home grower get seeds?

A: I actually never recommend starting a marijuana plant from seed, because you have to determine whether the seeds are male or female, which is difficult. Only female plants produce the flowers that are most desirable in terms of cannabinoid content. Male plants are pretty much unusable (for smoking purposes).

The best thing to do is to buy a clone — a cutting from a proven plant. People who have red cards (medical-marijuana cards) can buy clones from medical-marijuana centers and grow their own plants. If you know somebody who grows, it is legal today (under state law) for a 21-year-old (or someone older) with a marijuana plant in Colorado to give another 21-year-old (or older) a clone from that plant.

Q: Tell us about the different strains of marijuana. How would people choose one?

A: There are three types of cannabis — indica, sativa and ruderalis.

Ruderalis is a ditch weed found in Europe with low THC content. The marijuana we’re familiar with is indica and sativa. Indica has higher CBN (a type of cannabinoid) content, which relieves pain and makes you lethargic. Sativa has the highest psychoactive content, is energizing and provides lucid thought. Most everything available today is a hybrid (and) carries the characteristics of both indica and sativa.

Indica-dominant hybrids are good for growing indoors, because they only get 2 to 3 feet tall from the top of the pot, with a diameter of 12 to 18 inches.

Q: Isn’t hemp a type of marijuana? Can that be grown in a house?

A: Hemp is basically a cultivated variety of sativa. For several thousand years, it has been bred for tall growth, fibrous stems and low THC levels. It still has the medicinal cannabinoids, but you need so many hemp plants to get valuable cannabinoid content — more than 100 — that it wouldn’t be worth growing at home.

Care, air and food

Q: What’s next after obtaining clone plants?

A: Place the clone in a pot filled with a planting medium. Although potting soil would technically work, we use a soilless growing media made from coco fiber, worm casings, perlite and vermiculite because it’s developed specially for marijuana, even though (manufacturers) don’t admit that. You can get premixed versions at grow stores — Royal Gold Tupur is a good brand.

A lot of people use hydroponics, where plant roots are free flowing in what is essentially a circulating water bath. But that can be a problem for inexperienced growers, because if you accidentally add too many nutrients to the water, you can burn or kill the plants because the roots suck the extra nutrients right up. Soilless media act as a buffer to protect the roots.

PHOTOS: Images from Denver Relief, a marijuana growing, dispensary, and consulting business

Q: What type of container is used?

A: Many people use 5-gallon plastic buckets, but those create problems because the roots just wrap around themselves and form a large root ball. If you use a 3- to 5-gallon fiber pot, the root sticks through the pot and (the plant) air-prunes itself, while feeder roots grow in the pot. That gives the plant a larger nutrient intake.

Q: How are the plants fed and watered?

A: Most nutrient products in hydroponic stores come with very easy-to-understand directions and a “recipe” and schedule on the side of the package that you can follow. You should also water the plants every two to three days with tap water that has sat in a container for 24 hours to let the chlorine evaporate.

In addition, because you aren’t growing the plants outside where carbon dioxide is abundant, you must supplement the indoor air with it. Many small-time growers use CO2 tanks (similar to those on a soda fountain machine) with a regulator valve. You can get these tanks from grow stores or beverage suppliers. You can also buy automatic controllers for the tanks that release CO2 at the ideal ratio of 1,250 to 1,550 parts per million.

Q: What gets done with the plants after they’ve been potted?

A: Start with clones that are 4 to 5 inches tall, and give them 24-hour light until they reach 9 to 15 inches. If you keep temperatures below 80 degrees, this takes four to five weeks — less if you’re growing hydroponically.

Then you want to throw the plants into the flower cycle (12 hours of light followed by 12 hours of dark). During the second to third week of flowering, prune the bottom third of the plant so it puts its growth energy into the top once buds form.

Q: Then what?

A: Most plants are ready to harvest after 65 to 70 days of flowering. A good way to tell if the plant is harvestable is to get a 45x magnifying glass from a grow store and check out the trichomes on the flowers. Trichomes are the translucent resin glands that contain the cannabinoids. When they turn amber or a milky purple, you know they’re ready. This sounds difficult, but it’s actually pretty easy for the layman to do.

Another option is, if about 80 percent of the flower’s pistils turn orange or darker brown rather than white, then they’re ready to harvest.

Processing the harvest

Q: OK, say a home grower successfully gets three pot plants to the final flowering stage. They’re healthy and producing buds. How are they processed?

A: When a plant is fully mature, some people cut it off at the base, then cut off the fan leaves and hang it upside down. After it’s dried, they’ll trim off all the outer “sugar” leaves (the single leaves close to the bud).

What we think is best is to take down the plant and cut off all the leaves at once. If you leave the sugar leaves on, they may make the marijuana harsher. We trim so the (flower) bud has a clean egg shape, and use (the sugar leaves) to make concentrates to smoke, vaporize or cook with.

Then you hang the plant upside down for about a week, until the stem snaps rather than bends. Conditions should be about 68 degrees with 50 percent humidity. If the plant dries too fast, it locks in the chlorophyll, making it taste like plant material instead of marijuana. If it gets too humid, it can mold.