The coir plugs are produced from coconut husks and are considered a renewable resource. They have a neutral pH and don’t seem to affect the pH of the water. Peat plugs are produced by stripping layers or mining bogs. In the last decade ecological questions have arisen about this practice. Peat has a low, or acidic, pH. Obviously, the pH should be adjusted for the different conditions. Coir has some of the same qualities of Oasis, a foamed plastic used as starter cubes. Clones do best in both coir and the plastic cubes at a pH of 6.3.
Peat cubes lower the pH of the water so the pH should be raised to 6.4 or even 6.5. To find out exactly what pH to use, check the peat’s pH. Figure out how much lower than 6.3 the peat measures. Then raise the water’s pH by that amount. Finally, after watering, check the pH of the drain water. It should be about 6.3. If it’s off, tinker around with the irrigation water pH, until the drain water does measure 6.3
Many people use Rockwool starter cubes for cloning. They are made from spun basalt rock. There are ecological problems related to their disposal. A lot of used rockwool winds up in dumps. Rockwool has a very high pH, especially when it’s new. I found that it produced spectacularly when it was buffered in a low pH water, 5.8, for at least 12 hours before it was used. The irrigation water was adjusted to 6.1.
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