5 Things Newbie Cannabis Growers Need to Know
Growing amazing cannabis is not as simple as merely planting and watering. There are many factors contributing to those healthy plants and big buds as Jennifer Martin explains.
Growing cannabis can seem easy at first. Just put the plant in some soil and add water, right? Well, yeah, if you want a little bit of B-grade cannabis. But most newbie growers have their hopes set higher. We all want to see our plants meet their genetic potential. For this, we have to avoid pitfalls and dial things in. Here are five major things that must be handled properly in order to get good results, no matter what your experience level.
1. Size the Container to the Plant
Small plants need small containers, and bigger plants need bigger containers. If you plant a small plant in a medium or large sized container, the media/soil won’t dry out fast enough, and the plant will become waterlogged, which is synonymous with oxygen depletion. With a small container, however, the moisture level will drop more quickly, allowing the wet/dry cycle to happen frequently enough to keep the plant healthy.
You want the container to dry out every one to three days. If it takes more than three days to dry out, then your plant won’t be at its best. If it takes less than one day, it might wilt or die before you get to it the next day.
A good rule of thumb is to plant clones or seeds into three-inch pots, then transplant to one-gallon pots once they are drying out in one day or less, then transplant again into 3-5 gallon containers once the one-gallon pot is drying in one day or less. For most growers, you can finish the plant in the 3-5 gallon container. If you are growing big outdoor plants, you’ll need to transplant at least one more time into a bigger container or soil bed.
The point is, you want the plant to dry out quickly enough to let fresh oxygen into the root zone, but not so quickly that it can die before you get to it each day. Therefore, sizing the container properly is essential to the health and performance of the plant.
2.Use Well-Aerated Media
Another major component of achieving proper drydowns is the aeration of the media. This is equivalent to the granularity of the media, or the amount of perlite or equivalent aeration material that is added. Fifty percent perlite to 50 percent peat or coco is a common ratio for good aeration. You are looking for the water you apply to rapidly sink down through the media. If it pools up on the surface, you need more aeration.
Further, with more aeration, you get quicker drydown, which has the equivalent effect of using a smaller container without actually having to use a smaller container.
3. Bugs and Diseases Are Trying to Get Your Plants and Will Probably Succeed
This is such an unfortunate reality for cannabis growers! Most clones come with bugs or diseases, and sometimes it can take a month or more to realize it, even with careful inspection. Outdoor plants will often attract mites, whiteflies, caterpillars, gnats, and aphids, just because these bugs are common on lots of different types of plants. Even indoor plants can easily get gnats and aphids. Gnats find a way to fly in, and aphids get brought in on ants. Another major source of bug infestations is people. Your friend who is helping you with your garden probably just came from another garden and brought some hitchhikers along for the ride, so seal your rooms well and put people in scrubs and crocs before they can enter. Either that, or keep everyone out (which is much safer, but less fun!).
If you manage to avoid all of the bugs, powdery mildew (PM) is the next threat waiting around the corner. Powdery mildew spores are in the air almost all over the world. Under the right conditions, they are happy to take up residence on your plants, which is a direct threat to your harvest. To avoid PM, you can run a sulfur burner two hours per night during clone and veg stages of growth. Do this when no humans or pets are in the room. Don’t run sulfur past the second week of flower, though, because it will make your flowers smell and taste like sulfur. The positive news is that good air circulation, a clean growroom, and a sulfur burner go a long way to keeping PM out of the room.
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4. Too Little Light is Better Than Too Much
Newbie growers often have the idea that plants like light, so it’s a good idea to give them a lot of it. Quite the opposite is the case. Plants have a certain tolerance for light intensity depending on their age, health, and the amount they are already accustomed to. A general rule of thumb is to start with low light and work your way up, increasing the light intensity (either by turning up the lights, or lowering them closer to the canopy) by 10 percent every few days. Any time plants show stress, reduce the light, even if intense light is not the cause of the problem. Wait until the problem has resolved, then begin increasing it again. The risk of too much light is a lot more catastrophic for your plants than the risk of too little.
5. Last but Not Least — Manage pH and EC
This is the most common oversight of newbie growers, probably because it costs a couple hundred bucks to get set up to do it, but it’s critically important to the performance of the plant.
pH (potential of hydrogen) is a measure of acidity and the root zone needs to be within a certain range in order to properly consume the nutrients. This range is roughly 5.7-6.6, but some cultivars can be more tolerant of wider ranges. pH meters come with sensor probes that have glass bulbs on the end that are sensitive and must always be kept moist. They go out of calibration frequently so they must be recalibrated, using 4.0 pH and 7.0 pH calibration solutions every couple of weeks. If they accidentally dry out, they may never be accurate again, but at the very least, would need to be soaked in calibration solution for an hour and then recalibrated. It’s kind of a pain to deal with pH meters, but the difference between doing it and not doing it is night and day in terms of plant response. You really can’t be a good grower without good pH management because your water, your nutrients, and your media all effect pH, and you can’t trust them to maintain their own balance.
Nutrient levels can be measured by the same meter, and are measured using units of EC (Electrical conductivity). Electrical conductivity is a crude measurement of the total amount of nutrients in your water. Some growers also refer to nutrient levels as PPM but this is a less reliable measure because some EC meters convert to PPM by multiplying by 500, and others by multiplying by 700. It’s becoming more common these days for everyone to use EC so there won’t be any confusion.
Cannabis likes an EC in the root zone between 1.8 and 2.5. It should be kept closer to 1.8 when the plants are small but can be up to 2.5 when they are larger and more mature.
Successful growers monitor their pH and EC with each watering. They keep a log of the pH and EC of the water going into the plant, then collect runoff to see what those readings are coming out of the plant. The runoff reading tells you if you must immediately correct an out-of-range root zone, or if you are in range and can just continue using the same input measurements with the next watering. If the EC of your runoff is below 1.8 or above 2.5, or if the pH is below 5.7 or above 6.6, you should correct your input settings and immediately fix the root zone conditions. If you don’t, the plant’s growth will slow down and it will get sick, and this can happen within 24 hours. This is because it can’t use the water that’s in the container since the pH and EC are not in their sweet spots.
Let’s look at some real-world examples of how to handle out-of-range root zone conditions:
Example #1. If runoff has a reading of 5.4 pH, the mixture to be added should be around 6.4 pH to bring the root zone up closer to 6.0 pH.
Example #2. If runoff is 6.7 pH, the mixture to be added should be 5.3-5.4 pH to bring the root zone closer to 6.0 pH.
Example #3. If drainage has a reading of 1.4 EC, 6.0 pH, the mixture to be added should be about 1.5 EC, 6.0 pH, to bring the EC up above 1.8 EC without changing the pH.
Example #4. If drainage is 1.2 EC, 6.7 pH, the mixture to be added should be about 1.6 EC, 5.3 pH, to bring the root zone closer to its ideal of 2.2 EC and 6.0 pH.
Example #5. If drainage is 3.0 EC, 5.4 pH, the mixture to be added should be about 1.0 EC, 6.5 pH to bring the root zone closer to its ideal of 2.2 EC, 6.0 pH.
I’m sure the prospect of managing and calibrating pH probes, as well as collecting and measuring all that input water and runoff sounds labor intensive, but it really makes a world of difference. Hardly any nutrient/soil combinations maintain pH and EC without regular human intervention, so although you might just be getting started as a grower, wrapping your head around pH and EC management, as well as the other four points above, will quickly bring you to the top of your game and seriously improve your chances of harvesting some great cannabis early in your cultivation career.
Written by Jennifer Martin | Cannabis Cultivation Consultant
Jennifer Martin is an indoor cultivation consultant who specializes in custom nutrients, propagation, and vertical LED facility design. She is the winner of the 1998 Bay Area Cannabis Cup and currently advises and educates cultivators on the West Coast and in Hawaii. She can be reached at cannabiscultivationconsulting.com.