Can hard water affect my weed?

The quality of water in cannabis cultivation is fundamental. It can make a difference between a large crop or a crop with problems since its inception. Most growers use tap water, which depends on the geographical area can show great variations from one to another. These variations are commonly known as hardness .

Water hardness is the concentration of magnesium and calcium salts in a given amount of water. Hard water has a high concentration of calcium and magnesium and soft water contains very little. Water hardness basically depends on the geological formations that water passes through. Limestone soil aquifers have a higher hardness, and silicate soils have soft water aquifers.

The effects of a hard water or soft water can be checked in our day to day. For example, in hard or very hard water areas, soaps make less foam since calcium and magnesium react with their compounds and cease to be effective. Also in appliances, which have a lower durability in hard water areas due to the lime scale that forms. Even an excess of calcium and magnesium is harmful for our body because it consumes hard water, but also a lack if soft water is consumed exclusively.

The same happens to plants. Calcium and magnesium are two essential nutrients for their development and an excess or imbalance can cause alterations. The continued use of hard waters forms lime inlays in the roots of plants, which means that they cannot absorb nutrients such as calcium, magnesium and phosphorus among others. Excess magnesium is not usually due to the use of hard water, although it can block calcium absorption.

The continued use of soft water, meanwhile, usually causes the typical calcium and magnesium deficiencies. These are accentuated in hydroponic crops, since they are generally two nutrients also present in soils. When a large amount of substrate is used, there are usually no deficiencies throughout the crop. In small pots, the plant comes to consume them quickly. In addition, even when present, in cold and humid climates their assimilation by plants can be reduced.

Today some manufacturers offer special fertilizers for cultivation when hard or soft water is used. But it is not usual, and most of them use minimal amounts of calcium and magnesium. The reason only for not creating excesses of these salts when starting from hard irrigation waters, at the cost of sometimes creating deficiencies if soft irrigation waters are used, either by their nature, or achieved by methods such as landslide or osmosis.


The only solutions are to reduce its hardness with soft water, or completely eliminate the salt content by means of an osmosis filter. Without a doubt, the second option will be the most beneficial in the long run, both for our plants and for our health and that of our appliances. When the crops are small or short-lived, mineral water can be used to mix it with the tap. A bottle may last us one or two weeks. But when the cultivation is continuous, it will not be profitable to have to buy large quantities of water.



The best solution is to use a calcium and magnesium supplement. Most cannabis fertilizer manufacturers market them. The doses to use are generally very low and a pot will last many crops. And the concentrations of both elements are appropriate for the cultivation of this species. Dolomite or epson salts can also be used when preparing the substrate mixture. They are slow-release, will be present in the substrate for many weeks and the plant will assimilate them when needed.

Bud S. Daily

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