One sign of an inexperienced grower is the tendency to blame outside forces for existing plant problems. Rare viruses and difficult-to-pronounce diseases usually top the list. Blaming rarities takes the attention away from the grower, and re-directs it to forces that are seemingly outside of the grower’s control. If upper management has no previous cultivation experience, they have no reason not to believe their Head Grower, so they grab a blank check and head down the rabbit hole together in an attempt to stop the mysterious forces from killing their crop.
The reality is that 95% of plant problems are due to sub-optimum growing conditions. Viruses or funky diseases seldom show up on their own and decide to decimate a crop. Rather, the grower allows the cultivation environment to slip outside of the optimum parameters for healthy plant growth. Insects, fungus, viruses and bacterial infections attack weak organisms first. By forcing a plant to grow in less-than-optimum conditions, a grower decreases the plant’s ability to resist attack.
Here are the 5 most critical growing parameters to keep in mind:
1. Sunlight. Cannabis thrives on direct sunlight, and a crop should receive a minimum of 6 hours of direct sunlight per day. Light intensity should be in the range of 800 to 1200 micromoles for excellent flower production. If you’re not reaching these levels, consider supplementing natural sunlight with grow lights.
2. Temperature. The optimum temperature range for cannabis is 20 – 30 degrees Celsius, or 68 – 85 degrees Fahrenheit. Night temperatures should not regularly dip below this level, and the heat of the midday sun should not exceed it. Of course, cannabis can grow outside of this temperature range, but growth will be slower, the yield will be less, and the plant will be more susceptible to disease infection.
3. Irrigation. The goal is to irrigate plants when they need water. Although this sounds simple, over-watering and under-watering are two of the most common causes of plant stress. Too much water will suffocate the root system since the overabundance of water in the substrate depletes oxygen. On the flip side, allowing a plant’s substrate to go too dry will cook the roots and render them useless. Irrigate a plant when the substrate dries down to 50% of the weight of a fully irrigated pot.
4. Airflow. Regular air movement prevents the creation of stagnant microclimates around the leaf. If the air is still, there is no exchange of C02 and the photosynthetic process will be compromised. Also, regular air movement is critical to help prevent the germination of fungal spores on the plant. Use circulating wall-mounted fans, vertical airflow fans, horizontal airflow fans, massive air extractors or just a good old-fashioned nice breeze to help guarantee adequate airflow throughout your crop.
5. Water quality. Irrigation water should have a pH in the range 5.8 to 6.2 for hydroponic operations, and slightly higher for organic cultivations. Electrical conductivity should range from 0.5 for recently rooted cuttings, up to 3.5 for healthy flowering plants. If pH values are outside of this range, the plant cannot consume the nutrients in the substrate. If the electrical conductivity is too low or too high, the plant will begin to cannibalize itself for food, or exhibit stalled growth as a result of nutrient toxicities. Keeping your irrigation water within the ideal range will give your crop the best chance possible of avoiding insect or disease attacks.
The next time your Head Grower starts blaming mysterious forces for a crop failure, remind them to circle back to the basics. Most likely, mysterious forces aren’t killing your crop. It’s your grower.