already using dolomite lime as a magnesium source. Soil that measures a pH above ‘7’– or one that is high in potassium (K) and/or calcium (Ca), which compete with magnesium for uptake by the plant – can be replenished via applications of the salts. Such soil may not react as well to a direct granular or dissolved application; plants grown in this soil tend to respond much better to a foliar spray or full watering with Epsom salts.
Large-scale outdoor growers in the Pacific Northwest (and gardeners in the Southeast) often struggle with depleted local soil that must be turned and treated before cuttings or seeds can be planted. Prepare your substrate by mixing in one teaspoon of salts per gallon of soil, then planting seeds, seedlings or clones – magnesium sulfate can account for faster germination. If you prefer, you can wait until your seedlings are a few inches tall, then water them all with a highly-diluted Epsom salt solution. Cuttings – which can be notoriously difficult to root in their new environment, depending upon strain and clone health – may potentially take hold more quickly and experience less shock as a result of this soil treatment.
Dosage for Dissolving Epsom Salts in Water:
Smaller-scale and indoor growers benefit more readily and consistently from dissolving the salts into water rather than soil. In a watering can or barrel, combine up to two tablespoons per gallon of water – first mixing the salts with a bit of warm water to thoroughly dissolve them. This can be given to the plants every four to six weeks, if necessary.
To apply a foliar spray, dissolve up to one tablespoon per gallon of water and spray Cannabis plants at the beginning of each cycle or when needed, focusing the majority of the fine mist upon the underside of the leaves. Avoid spraying your plants past the first few weeks of flowering, or while the lights are on; if you must spray them during the ‘daylight’ cycle, allow the plant to cool down before and after – and dry off – before turning the lamps back on. It is more effective, however, to spray the plants when both they and the room are cooler in temperature.
Epsom Salts to Revive Mothers or Root-Bound Plants:
When plants remain for too long in the same pot, they can suffer from salt buildup and become nutrient-locked and/or potbound. An easy and gentle Epsom salt solution will dissolve the accumulated salts and allow the plant to regain healthy circulation by unclogging its root cells. This is especially effective in plants that require direct sunlight – a category in which Cannabis is firmly listed – due to the importance of magnesium sulfate in photosynthesis.