Article by The Rev, Skunk Magazine
HEY HEYEVERYONE; I hope this article finds you all baked and happy. Today I wanted to babble a bit about magnesium (Mg) and cannabis growing. Cannabis is a seriousconsumer of Mg, especially during the flowering cycle, but … too much Mg is highly destructive to your living soil, especially effecting soil structure, which will mess with the aerating abilities of your soil, hence hurting all the soil microbeasties; if the microlife is not happy and healthy, neither are your plants. So, what I’m going to do here is just give you all a rundown addressing Mg, how to safely add it if needed, and how to avoid an Mg overdose. I’ve been doing this growing thing now for almost half a century (44 years) and I am a decent observer of detail and patterns when it comes to cannabis, so hopefully I can help many of you out here. Let’s check this out shall we…
Looking at that photo with those flowering plants 5 days from harvest showing ‘awesome’ Mg deficiency; and I say awesome, because Mg is one of those elements in cannabis that does not smoke well (and is in fact really harsh). So, you always love to see the Mg deficiencies this close to harvest if you are aiming for thee tip-top shelf finished product. You growers that are all tea crazy, using decent amounts of molasses in your teas, you need to know that molasses packs a big Mg punch; so, translated that means you should lay off the molasses usage by about halfway through flowering. You always want to have a grip on all (globally) your mineral type inputs—like the Mg in the molasses—because other elements can get deadly too, fast, when a bit too much is added, like potassium (K), or sulfur (S), as two other examples.
Again, referring to those plants in the photo with the good kindof Mg deficiency, you will see how the larger leaves in about the middle of the plant are really getting yellow/chlorotic. These are classic Mg signs here folks; and those leaves aren’t just yellowing, they show ‘interveinal chlorosis’ yellowing, which simply means that the veins of the leaves stay green while the rest of the leaf yellows between those veins. That’s how you can spot a Mg deficiency on flowering plants especially. It should be noted here that I run rich levels of Mg in my own soil blends, with my largest contributor being dolomite lime. I occasionally need to amend with additional Mg; some genetics just “crave” more Mg than others, so there’s always that to keep in mind.
See in the photo how the tips of the leaves are curling upwards? This is highly likely in my experience to indicate an early stage of an Mg issue. This is what I would call an early warning flag, and no need to fear if you see this, just keep an eye on the newest growth for the next 10 days or so. I normally find this situation fixes itself as the plant and the soil life work in concert to make more of the Mg in the soil available to those plants. Put your thinking caps on and go over everything going into your plants, mineral-wise, and especially Mg & calcium (Ca). Dolomite lime in your soil mix is the best way to proactively handle this. But I have found other ways to amend and check for Mg issues, so let’s have a look at those now.