Every professional grower knows to flush cannabis plants with plain water before harvesting. But when’s the best time to flush, and how much time should be spent doing it?
Flushing is a simple process for both soil-grown and hydroponic plants, and it can make a big difference in the taste, purity and smoothness of cured flower. Whether you are entirely organic or use chemical nutrients, a plant will taste best and smoke smooth when the time is taken to flush.
Flushing also lets the plant use the storehouse of nutrients, minerals and salts that are left over each time it gets watered. These leftovers help fatten the buds as the plant puts this stored energy to good use.
On the other hand, not flushing your plants can leave behind trace elements that can make the product harsh. Some nonorganic nutrients can mask the real taste of the strain if not fully flushed out. Flushing is especially important if you make concentrates, since any leftover salts, nutrients and minerals will be concentrated down to the oil.
The question of when to flush and for how long becomes each grower’s choice, based of what they want in the final product. It depends on your choice of nutrient lines and their application strengths. The shortest amount of flush time would be seven to 10 days, which can still leave trace minerals in the final product. So, the best practice for flushing is to begin no more than 14 days before harvest. This will give your plants the maximum amount of time to feed on their reserves. But flushing longer than that can sometimes cause issues with loss of potency and weight.
Flushing for the last 14 days can start from the time you see that all or most of the trichomes are cloudy. If you want a more “couch lock” product, start your flush as soon as you see some amber color in the trichomes. For a more energetic high, initiate the flushing when you see that a majority of trichomes have turned cloudy. This will allow the buds to finish before you see any amber during the final days.
Mark your grow calendar when you initiate the process. Use your handheld microscope (a must-have tool for this time in your grow cycle) to watch the resin turn more cloudy or more amber. After ten to 14 days, you should be ready to harvest.
There are products (such as Clearex) for flushing plants that are in nutrient lockout during flowering, or in other emergency situations such as over-fertilizing. But for your final flush, using plain water is helpful in bringing the overall costs down for the last few weeks of each cycle.
Simply put, you should use with reverse osmosis-cleaned water that has been pH balanced. This allows the plants to use the nutrients left over efficiently. Water as you usually would, but don’t add nutrients or additives. If you are a hydro grower, fill your reservoir as normal and change your tank every four to eight days so that the water remains clean.
During this period, your plants are no longer being fed nutrients during your water cycle but are pulling them, first from the soil, then from the roots and finally from the bigger fan leaves. When the flushing process has reached the fan leaves, they will begin to yellow and turn lighter as they send the stored nutrients to the flowers.
The flowers will fatten up during these last few weeks while flushing; this can be up to 25 percent of the final weight. As they finish, the roots and “water leaves” send energy reserves to the flower. Each flower uses these stored reserves to make more resin, weight and potency.
Also, as you count down the days to harvest, continue to love and pay attention to your plants. The end of an excellent harvest is about simplicity, as you let the plants do what comes naturally at the end of each flowering cycle. Focus on keeping the buds in good shape as they become denser but more susceptible to molds and mites.
And have patience. Being patient is paramount to bringing in a clean, smooth and healthy product every time.
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