Micronutrient deficiencies in cannabis – these sorts of deficiencies aren’t as important as macronutrient deficiencies, but they’re still essential for your plants to be healthy. There are many kinds of micronutrients but some of them are more common than others, and others are rarer in as far as deficiencies but you still need to know how to recognize those deficiencies.
Micronutrients in cannabis are calcium, magnesium, iron, manganese, copper, zinc and boron. Each one of these minerals is essential for your plants for many reasons; photosynthesis, transporting nutrients around the plant and for symbiotic activities – plants can’t photosynthesize without magnesium, but an excess of magnesium can block the potassium needed during the flowering period.
Your plants need all of these minerals in the perfect quantities, which can be hard to achieve but if you can recognize the deficiencies then you can easily correct the issue before it gets bad. Generally, your plants will show symptoms on the all of leaves when they’re lacking micronutrients, from the biggest to the smallest leaves, which is how you can tell that the issue is with micronutrients rather than macronutrients.
We’re going to go through a list of the different micronutrients, how to recognize deficiencies and how to fix them.
Micronutrient deficiencies in cannabis:
Calcium: This deficiency is easily spotted; it shows up through yellow spots or stains that are brown around the edges, and if you don’t stop it in time, the leaves will dry up and fall off; this will also cause vegetation or flowering to stop too, depending on which phase it’s in. This can happen due to not having enough calcium in the soil, which can easily be solved by adding some calcium into the irrigation water as a micronutrient or through a natural fertilizer like dolomite. You’ll need to catch this deficiency early as when it advances it is easily confused with potassium deficiencies, although potassium stains always appear on the edges of the leaf whereas calcium deficiencies can show up on any part of the leaf.
Magnesium: Magnesium shows up as yellow stains on your plants, similar to calcium however the brown edges don’t appear until it’s very advances. It doesn’t tend to have many negative effects and it’s hard to catch in time – the plant sucks the nutrient from the leaves very slowly, so the actual deficiency itself shows up extremely slowly too. It would be fatal for your plants to have this deficiency at the beginning of the flowering period as this is when your plant needs magnesium the most. If it shows up towards the end of the grow then you shouldn’t worry as it’s quite normal. It can be fixed by adding some magnesium to your irrigation water or adding Epson salts to the soil. If you’re using osmosis water, then you’re better off using Epson salts in the soil once they begin flowering to avoid any sort of magnesium deficiencies.
Iron: This deficiency tends to show up on the smallest leaves, and they tend to suffer from chlorosis or a discoloration of the entire leaf save the veins; they will slowly turn yellow until they fall off. It’s quite hard for your plants to develop this deficiency, but it does happen more frequently in mother plants or plants that suffer a lot of stress during the vegetation period like plants that are pruned a lot or plants in SCRoG systems which involve bending the branches. Basically, any plants that get much too stressed out can develop this deficiency. The solution is that, if you know you’re going to be stressing your plant out, make sure to give it a fertilizer rich in iron in your irrigation water before stressing the plant out to make sure that is has enough iron so that it doesn’t need to take any from the leaves.
Manganese: Manganese is present everywhere in your plants and is directly related to nitrogen absorption – a lack of this nutrient will cause your plants to stop absorbing nitrogen which can be devastating for your plants. It also affects the creation of proteins in your plants so the growth period will slow down quite a lot. The plant will begin yellowing all over, and although it might look like it’s losing all of its nutrients it’s just nitrogen. This can make for some horrible flavors in your weed if it happens towards the end of the grow. You’ll notice the plant getting yellow from the edges of the leaves towards the inside, leaving the central vein in the leaf green. You can fix this deficiency by enriching the soil with a fertilizer rich in manganese during the growth period, and a little bit at the beginning of the flowering phase.
Molybdenum: Molybdenum is the substance that fixes nitrogen to the plant, and your plants really don’t need much of it. It tends to be in boosters used at the start of the flowering period which helps stop growth and push the plant into flowering. It’s rare for plants to show deficiencies of this micronutrient, although it can appear in grows where the pH isn’t properly adjusted and the soil is too acidy. If your plants show this deficiency during the flowering period then the leaves will go yellow just like a manganese deficiency, although these leaves will rot and dry up. You can fix it by applying the micronutrient alongside a fertilizer rich in phosphorus which will help it to be absorbed. If you use it during the pre-flowering as a flowering stimulant (that contains molybdenum of course) then you’re guaranteed a successful grow without any nasty surprises.
Copper: Copper is a mineral that’s directly related to the plants’ immune system, especially when it comes to fungi. If your plants show a deficiency of this mineral then fungi like oidium and botrytis will be all over your plant as soon as they can. You can tell this is happening because your plants will look droopy even if you’ve watered them, and new sprouts on the plant will dry up and fall off. If you don’t catch this one fast enough your plant will turn to dust within days, especially if it’s very new. You can use a foliar spray rich in copper like some fungicides – this will fix the deficiency and protect your plants from fungi.
Zinc: Zinc is an indispensable mineral in your cannabis plants, as it’s needed to create chlorophyll and that obviously has repercussions for the entire plant, especially during the vegetative phase. This tends to occur in plants where the soil has a high pH level and in grows where too much flowering fertilizer has been used. If you wash the roots out too much this can also happen. The best way to solve this deficiency is to spray your plants just once with some liquid zinc solution. Make sure not to spray too much as an excess can be toxic for your plants. It’s detected generally through a complete stop in growth, the leaves get long and thin. You’ll need to take care with this mineral.
Boron: Boron is fundamentally involved in creating the plant’s cellular walls, so small deficiencies are easily distinguishable in small sprouts that haven’t grown yet. These deficiencies cause brown stains, kind of like burns or rust stains. This tends to happen in grows where too much growth fertilizer has been used, and the excess nitrogen blocks the absorption of boron. It also happens in grows where the substrate has gotten too dry, which makes boron rise to the top in the soil and the roots can’t get to it to absorb it. Plants that get a decent amount of boron and a pH between 5 and 7 should have a decent flowering period, a nice calcium absorption and the buds wil get even fatter.
Now you know what kind of micronutrient deficiencies that your plant can have, how to prevent them and what you can do to solve them if you catch them too late. Keep in mind that excesses of certain nutrients can cause deficiencies, but that’s a topic for another article.
- The Stag
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