Introducing our new column about cannabis cultivation: Renowned grower Jorge Cervantes will answer readers’ questions and give advice on all things related to the cannabis plant. Got a question for Jorge? Email him at firstname.lastname@example.org.
Editor’s Note: Laws for cultivating cannabis vary from state to state and city to city — before germinating any seeds or planting any clones, take care to learn what your local laws are.
Question: In Colorado, we can grow cannabis at home legally. But we have to do so indoors. But I’ve started to take my plant (packed into a reusable grocery bag filled with soil) into the backyard with me on sunny afternoons to soak up some rays as a respite from the grow lights in my basement. Is that mix of grow lights and natural sun good for my plants?
Answer: Yes! Your plants love you for the natural sunlight too! Natural sunlight contains a much broader spectrum of light than most indoor grow lights. While most sunlight consists of infrared and visible light, there is a small but important percentage of ultraviolet (UV – UVA, UVB, UVC) rays. This is the portion of the spectrum that gives us a suntan. Plants love it too, but, like humans they must become accustomed to it over time.
Setting plants out for a few hours in full sun works well, but keep an eye on them for the first week. Moving plants into bright sunlight that contains UV rays is a big shock for young tender plants and they require several days to “toughen-up” to the outdoor weather.
You might try setting them out in the shade or partial shade for the first 2-3 days. They should be able to take full sun for 4-5 hours within a week. By the end of two weeks they can take full sun all day long.
Inspect plants regularly and control for diseases and pests. Soft indoor leaves are easy-to-penetrate by pests. Once plants toughen up, diseases and pests find them less tasty.
Be gentle with the thin-skinned reusable grocery bag. The soil can shift in such a bag and when it does roots get broken. You might consider placing the grocery bag into a more rigid container that will prevent against jostling the soil around.
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Shade the container from bright sunlight. Soil temperatures near the perimeter of the container can rise to more than 140 degrees in a short time of sunbathing. Many cannabis roots encircle the perimeter of containers, and the hot temperatures cook roots.
Roots start to rot when dead and moist conditions prevail. Plants are then shuttled into a cool basement grow room where conditions for disease are perfect. Once the rot sets in, associated bacteria, fungi, etc. start to colonize the roots and soil and attack other roots. Most often gardeners do not notice the problem until it is advanced, and the problem is easy to misdiagnose.
Shield plants from wind if necessary. Indoor plants do not develop a strong stem and when placed outdoors, it takes about a month for plants to grow more cellulose to strengthen stems. A little bit of wind is good for plants, but too much will dry them out quickly. For example, I had to give plants seven times more water when growing 1.5 miles from the Mediterranean Sea because of the constant wind. Once I set up a wind-block made from permeable shade cloth, water consumption went from two gallons per plant to one-half-gallon per plant.