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ph levels for germinating cannabis seeds

Photo: yellowing, leaf curl, circular burnt spots on leaves, and leaf drop are typical symptoms from water with a high level of sodium.

Failure to adjust the pH to the desirable range will result in several negative symptoms, that will range from mild to chronic, depending on the severity and duration of the pH imbalance:

For germination and seedlings you should always use high quality water: “soft” mineral water with pH 6.5 and low levels of sodium is best. The pH should be adjusted to the ideal range with vinegar so that there are no salts which can inhibit germination or damage the seedlings. In hydroponics a very weak nutrient solution of EC 0.6 mS/cm (or 600 µS/cm) is usually used. For germination pure water is also sufficient until the seedling appears.

All of these factors influence how the pH should be adjusted and how it changes in the containers or tank over a period of time. A fluctuation of one full point in hydroponics can usually be tolerated by cannabis as long as the pH is stabilized to the ideal range within 24 hrs. For best results the pH should therefore be monitored daily in a system with large fluctuation.

Photo: this is a standard colour chart for a liquid pH tester. The optimum pH range of water for cannabis cultivation in soil is a light green colour that indicates pH 6.2-6.5

Tap water can be “hard” from high levels of calcium (Ca) and magnesium (Mg). The pH is in this case very alkaline. Chlorine is another common additive which causes stunted growth in plants and acidifies the soil. If your tap water smells from chlorine you should fill warm water into a bucket and let it sit for a few hours so that the chlorine can evaporate.

In the world of plants each plant species is perfectly adapted to a certain pH range of the soil or water. Hobby gardeners are usually familiar with the different pH requirements of various plants like rhododendron, roses, or conifers, and buy special soil mixes and regulate the pH of water appropriately.

In the world of cannabis growing, pH affects and is affected by everything. Indeed, the entire process of growing plants is a study in the physical dance of pH balance. Read on for an in-depth overview of pH as it relates to growing quality cannabis.

Hydro and soilless grows are a different beast when it comes to pH. If you grow soilless, say in coco, the optimal pH level at the root zone should be somewhat lower than in soil, between 5.5–6.5. The same goes for all methods of hydro.

What Is Soil pH?

Using natural fertilisers like compost, worm castings, and bone meal creates a breeding ground for healthy bacteria and fungi that keep the conditions of your soil optimal, so there’s usually no need to monitor the pH of your soil as closely as you would otherwise.

The benefits of caring for and maintaining your plants’ pH is pretty straightforward; you’ll have healthier plants that demonstrate more vigorous growth and, as a result, produce better harvests. Plus, you’ll also ensure that the time and money you’ve spent fertilising your plants is paying off.

In more scientific terms, pH level has to do with the concentration of hydrogen ions, say in the water you give to your plants. The pH scale is logarithmic to the base 10, which means that water with a pH of 6 is already 10x more acidic than water with a pH of 7.

pH Up is a strong alkali formula for raising pH. The one from General Hydroponics is made from a base of Potassium Hydroxide and Potassium Carbonate.

pH Down is an acid based formula for lowering pH. General Hydroponics up/down is made from a base of Phosphoric Acid.

As explained above, adjust the pH of your solution a little at a time. Try to use only either Up or Down. If you overshoot with one and then have to readjust with the other you can end up unnecessarily stressing your plants. Mix up a little of the required pH adjuster in a separate jug. Then add them a little at a time to your reservoir. Allow time for the whole reservoir to even out and settle. Better to get it right with 3 slight adjustments than have it wildly swinging up and down.