Analyzing When You Should Cease Nutrient Supply to Cannabis Plants

When it comes to cannabis cultivation, providing ample nutrients is essential to get the most out of the crop. For growers, it’s important to know when to stop nutrient supply to their cannabis plants in order to maximize production and harvest the most potent flower. In this article, we’ll discuss strategies for determining when to end nutrient input in cannabis cultivation.

Macronutrients vs. Micro-Nutrients for Cannabis Cultivation

It’s important to differentiate between macronutrients and micro-nutrients when discussing when to cease supplying nutrients to cannabis plants. Macronutrients, including nitrogen (N), phosphorus (P) and potassium (K), are primary nutrients required for healthy growth and development. Micro-nutrients, such as zinc, boron, manganese, and iron, play an important role in the growth of cannabis plants. These micronutrients are especially important during the flowering stages of development but can be beneficial at any stage.

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Signs the Plant Needs Nutrients

A key part of determining when to end nutrient supply to cannabis plants is being able to recognize signs the plants need more nutrition. For example, yellowing, fading or spotted leaves may indicate that the plants need more nitrogen or other macronutrients. Stunted growth and/or yellowing stems may indicate a lack of potassium and phosphorus.

Additionally, signs of nutrient deficiency vary depending on the type of plant and its growth stages. A general rule of thumb is that cannabis plants in the vegetative stage require more nitrogen, and plants in the flowering stage need more phosphorus and potassium. Growers should also keep an eye out for signs of nutrient burn, which can be identified by discolored and burned tips on the leaves.

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Daily Maintenance and Monitoring

Growers should maintain a regular schedule of monitoring their cannabis plants for signs of nutrient deficiency and nutrient burn. They should inspect leaves for discoloration and/or signs of burn as well as examine the stems and ensure that growth is consistent. Furthermore, growers should ensure that their nutrient solutions are balanced by keeping their pH levels in the optimal range (5.5-7.5). Maintaining daily monitoring and maintaining a balanced nutrient concentration is essential for getting the most out of cannabis crop production.

Testing Nutrient Salinity in Reservoir

Growers should also measure the salinity of their nutrient solutions on a regular basis to ensure that nutrient concentrations are in the optimal range. Excessive salinity in the solution can also result in nutrient burns and/or deficiencies. EC (electrical conductivity) and PPM (parts per million) tests should be done to measure salinity. Growers should ensure that the PPM isn’t over 800 in each reservoir, and their EC should be between 1.0-3.0.

Ending Nutrient Supply and Flushing the Plant

When it comes to determining when to end nutrient supply, growers should consult their local grow experts and/or their nutrient manufacturer’s instructions. Generally, growers should cease product input 1-2 weeks before harvest in order to achieve optimal bud development. After ceasing nutrient input, the plants should be flushed with a plain pH-balanced water for 3-4 days in order to remove any excess salts in the growing medium.

Harvesting and Drying

After flushing the plants, growers should move on to the harvesting and drying stages. Harvesting should take place when buds are fully developed and reach the desired levels of trichome and cannabinoid development. After harvest, the buds should be dried for about one week in order to maximize potency and taste. Finally, the buds should be cured for 4-6 weeks to facilitate optimal qualities and aroma.

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The Importance of Macronutrient Input

It’s important to remember that macronutrient input is essential for healthy plant growth and good harvest quality. Without proper nutrient input, plants will likely suffer from nutrient deficiencies that can drastically reduce yields or produce inferior buds. Because of this, it’s essential for growers to ensure their plants have access to the right amount of N-P-K throughout the growth cycle.

Nutrient Uptake and Ratio Timelines

Determining when to cease inputting nutrients to cannabis plants should also take into account uptake rates and timeline ratios. Generally, a grower should input nitrogen every 2 weeks, and phosphorus and potassium every 3-4 weeks. Additionally, the nutrient solution should be changed every 7-14 days. By doing so, a grower can ensure their plants receive the optimal amount of nutrition for healthy growth and maximum yield.

Soil Nutrient Availability

On the other hand, soil cultivation has more gradual nutrient availability, and generally doesn’t require changing of the nutrient solution as often. This can be an advantage; however, soil relies more heavily on amendments and dissolved organic material as a source of nutrition. Additionally, soil nutrients are released slowly, which can increase the risk of nutrient deficiencies or burning if not monitored properly.


In summary, determining when to end nutrient input to cannabis plants requires a combination of daily monitoring, soil fertility tests and knowledge of nutrient uptake timelines. Furthermore, growers should use a combination of macronutrients and micro-nutrients to ensure their plants are receiving adequate nutrition. Finally, they should take into consideration the typical nutrient uptake timelines and cease nutrient input 1-2 weeks prior to harvest to ensure maximum bud potential.

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