Overfeeding cannabis, improper pH levels, and other stresses on your plants can result in a nutrient lockout. Whether it’s salt buildup from nutrients or pH levels that prevent absorption, a nutrient lockout results in a buildup of nutrients in the soil while the plant cannot access them.
By paying attention to the trichomes on your plants, you’ll be able to tell when your plants are ready for a flush. If flushing two weeks prior to harvest, you should begin when you start seeing the first trichomes turn milky.
Flushing your plants will remove excess buildup of salts and nutrients while helping to restore the soil’s pH balance. This will allow your garden to resume absorbing nutrients and grow at a healthy, successful rate.
Think of it as someone changing their diet. You can fill your fridge with new types of food, but you might find yourself running out of room if you never removed the old food. By removing the old food, you are clearing a path and starting anew.
Once again, flushing cannabis simply involves running pure water though the soil or medium. When trying to stop a nutrient lockout or when switching nutrients, perform a flush by excessively watering your plants with water that has a pH level between 5.5-6.5 (for hydroponics) or 6.0-6.8 (for soil). Fully saturate your pots, and repeat 15 minutes later. The flush should clear any blockage and make room for your new feeding schedule.
There are three primary instances when flushing your cannabis is appropriate:
The only time flushing is not encouraged is when you are growing in amended organic soil. This is because your soil already holds all the nutrients the plants need to thrive. By flooding the soil, you can wash away and damage the complex ecosystem that you’ve worked so hard to develop in the soil itself. Furthermore, these plants almost always receive pure water during waterings. The nutrient uptake by plants in this environment is natural, diverse, and easy for the plant to process.
Once you’ve properly flushed and harvested your garden, it’s important to dry and cure the cannabis correctly. It is through a quality flush and a long cure that your cannabis will be able to fully express itself.
Trevor is a freelance writer and photographer. He has spent years in California working in the cannabis industry.
Flushing is when you stop feeding your cannabis plants nutrients and give them water. The process is generally as easy at it sounds, but it's crucial to know precisely when and how often to flush.