Calcium is vital to your harvest's proper growth. It facilitates the absorption of other nutrients, preserves cell structure, and facilitates photosynthesis. Thus, a deficiency or lack of the element has an impact on plants' development. Here we give you guidelines to identify the external signs of these alterations, and some tips on how to correct them.
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Like when dealing with a human disease, it is important to pay attention to the symptoms that your cannabis plants exhibit in order to know what is not working. If you have observed small brown or yellowish spots dotting the surface of the leaves, if your youngest plants are curved or taking on strange shapes, they might be sending you an important signal: they lack calcium.
Is calcium good for weed plants?
The signs first appear on buds and the edges of the leaves, but little by little they spread from there. Remember that your whole harvest will not necessarily be affected; although any strain can suffer from a deficiency, some are more sensitive, and certain plants of the same variety can absorb more calcium than others.
The external consequences are just a reflection of what is happening inside: this chemical element is essential for your plants’ development, falling under the category of secondary macronutrients. Don't let that adjective fool you: the fact that they are termed “secondary” does not mean that they are less important to plant growth than those dubbed “primary” (like nitrogen, phosphorus and potassium).
Plants absorb calcium through their roots, later transporting it to all their cells through xylem (the conduits that distribute the nourishment recently received by leaves and stems). Its absorption is very closely related to magnesium and iron, such that a calcium deficiency is usually associated with that of these two elements too. If a plant lacks calcium, neither will it be able to extract the potassium that it needs from the soil.
Too much calcium in your cannabis plant?
Too much is not healthy either, as calcium toxicity in plants will affect the absorption of the other nutrients. Moreover, when the concentration is too great the exchange of gases, taking place through specialised cells in the leaves, is blocked, also leading to the onset of chlorosis (“burned” areas featuring a brown colour) on them.
What do your marijuana plants need calcium for? In their roots, its presence is indispensable for them to acquire the right density and length. Once it has reached the cells, they use it to carry out a range of functions, including photosynthesis, the essential process by which they transform water and light into energy in order to live.
As in human bones, calcium also has structural functions, forming part of cellular walls and functioning like a kind of cement keeping them rigid. Thus, when they lack this “natural cement” the leaves and tips of the roots grow in strange ways, becoming curved or serrated.
Do weed plants need calcium?
Of course, calcium also regulates the action of the plant hormones responsible for the plant’s germination and growth, and stimulates the segregation of the enzymes that protect your cannabis plants from abrupt temperature changes (known as thermal stress).
Thanks to calcium, cannabis plants also have a protective shield against disease. The element participates in the activation of the defence mechanisms necessary to prevent damage from viruses, bacteria and other pathogens that destroy cellular walls.
And here is the really important part: when does calcium deficiency appear? Outdoor crops run a greater risk of suffering this deficiency, unless they grow in low-pH (acidic) soil, like that of a pine forest. This is often where the problem lies: an acidic pH prevents plants from getting all the calcium they need. So, if you are growing in organic soil, you’ll need to check its pH and make sure that it’s between 6.2 and 7.
Hydroponic plants, on the other hand, are more sensitive to a lack of the nutrient, as well as to pH variations. In their case, roots absorb the right amount of calcium when pH levels are from 6.2 - 6.5.
The type of water you use also makes a different. Sometimes tap water does not feature sufficient calcium levels and, if you use osmotic water (with no nutrients) you will need to add calcium and magnesium before fertilizing. The same is true if you use distilled water.
Many fertilisers include calcium in their nutrients, but if it is not enough it is a good idea to add a supplement with calcium and magnesium to your irrigation water, but be careful not to do so during flowering, because they also contain nitrogen, and your plants could absorb too much of the element. Using a calcium nitrate fertilizer is another possibility (while heeding the same warning), or getting one that contains only calcium, like the one you can find at our store.
You can also deliver the nutrient by means of hydrated limestone, which is to be added to irrigation water, or dolomite dissolved in water and applied to the leaves. Use any of the two solutions until the symptoms disappear (you will observe improvement on the new buds, but damaged leaves do not recover).
In order to prevent a lack of calcium it is best if the fertiliser that you add contains this nutrient, and to monitor the pH levels of the water and the substrate. In any case, if you detect a deficiency, the measures that we suggest here will help your plants to flourish, growing green and healthy.