How to Water Cannabis in Coco

Watering Coco: Watering Can and Cannabis Plants

How should you water cannabis in coco? How much, how frequently, and what do you pay attention to? This coco watering guide answers all your questions about how to water cannabis in coco. I include specific advice about how much water for each event and discuss how to determine your coco watering frequency. I also include a coco watering schedule to help you set the timing of multiple daily events.

Feeding and Watering Coco is "Fertigating"

When we water plants in coco, the water should always include nutrients. Therefore, we are “fertigating”, which simply means combining fertilizers with the irrigation water. Proper fertigation strategy is the central key to obtaining the best results from your coco grow. In “Principles of Fertigation”, I lay out the 5 key principles:

  • Principle 1: Fertigation is a Balance: Proper fertigation strategy balances the Nutrient Element Ratio (NER), which controls plant nutrition and the Electrical Conductivity (EC), which controls osmosis.
  • Principle 2: Always Fertigate: Add nutrients to all irrigation water! To maintain the balance between NER and EC, nutrients must be added to all irrigation water at the correct ratios and doses. The feed chart determines the ratio, and EC determines the dose.
  • Principle 3: Always Fertigate with 10-20% Run-off: Run-off carries away the excess salts and allows you to maintain a consistent root zone EC. Proper run-off practices are discussed below.
  • Principle 4: Fertigate Frequently: Do not let your coco get dry! One of the key benefits to growing in coco is that it enables high frequency fertigation. This article discusses just how frequently it should be.
  • Principle 5: Manage Electrical Conductivity (EC): You need to monitor the EC of the nutrient solution you are adding (inflow) and the EC of the water that drains through and ends up in the saucer of each plant (run-off). As discussed in our tutorial “How to Manage Run-off EC”, The critical number is the difference between the two. As explained below, fertigation frequency is one of the main ways that you maintain that difference in the acceptable range.

Coco Watering Guide

This coco watering guide explains in detail how to put these principles into action and water cannabis in coco like a pro. It explains:

  • The basics of watering coco
  • How to determine your coco watering frequency
  • The best coco watering schedule
  • And, how to handle run-off

To become a master of watering coco, be sure to read our articles “Principles of Fertigation” and “Understanding Osmosis and EC”. Also see our tutorials, “How to Set EC Targets”, “How to Mix Nutrient Solutions”, and “How to Manage Run-off EC”.

Watering Coco

Whether you water with an automatic watering system or by hand, certain principles should guide your strategy for watering coco:

Quantity is Determined by Run-off

You should always provide enough nutrient solution to each plant to produce 10-20% run-off. Under high-frequency fertigation, the quantity needed to produce run-off should be consistent. It should also be small. As discussed further below, the ideal quantity of water per event is about 5% of the volume of the growing container. This is ideal, but whenever you are watering coco, always provide enough water to actually produce adequate run-off from each plant.

Watering Coco is Best in Intervals, Not Continuous Drip

Watering coco frequently is best. However, it should not be continuously watered. Nutrient solution should be applied during events followed by an interval to air-out. The interval can be as little as 3-4 hours during peak needs, but water should not be continuously added to coco.

Ensure Complete Saturation

Every time you water cannabis in coco, the entire volume of the media should be saturated. If the media is not thoroughly saturated, salts will build up in the dryer regions and can burn your plant. Remember evaporation leaves salts behind and run-off flushes these salts. Therefore, it is important to flush the salts with each and every watering by properly saturating the media

Hand Watering: You should apply nutrient solution slowly and give it time to properly soak in and saturate the media. If you apply nutrient solution too quickly, it may not properly saturate the entire volume of the media.

Automatic Watering: Be sure to set up drippers that can properly distribute the water. See our tutorial, "How to Manage Automatic Watering Systems".

Coco Watering Frequency

There are three main ways to determine your coco watering frequency:

By Look and Feel:

The surface of the coco should never get dry! If you are familiar with growing in soil, you will certainly feel like you are over-watering in coco. When you are watering coco, it should still be moist from the previous watering. If the surface of the coco is dry, your coco watering frequency should be increased. The surface of the coco should never become so dry that it turns lighter brown.

By Volume of Water Needed:

You should water cannabis in coco frequently enough that about 5% of container volume produces run-off. This is less water than most growers assume. Quantities are small because frequency is high. Since you are never giving the coco much time to dry out, there is never going to be much capacity for it to hold more. As an example, in 5 gallons of media, it should take about 1 quart of water to achieve adequate run-off. If it requires more than 1.5 quarts to produce adequate run-off, coco watering frequency should be increased.

By Monitoring EC:

Early in the grow, you should use look and feel along with volume to determine your coco watering frequency. However, as the plant becomes established and is growing rapidly, you can also consider EC. When the difference between inflow EC and run-off EC becomes too large, watering coco more frequently is the preferred way to lower it. Obviously, there are limits to this, but it is difficult to overwater mature plants in coco/perlite. See our tutorial, “How to Manage Run-off EC”.

Start with DAILY watering:

You should water cannabis in coco at least once per day. For this reason, it is important that plants are always in appropriately sized containers. I start plants in pint sized containers and water the small seedlings once per day. After about a week, I transplant to half-gallon containers. Once they are established in the half-gallon containers, I begin watering twice per day. In final containers, plants may stay at twice per day through the rest of the vegetative period or increase to 3x daily watering depending on container size, climate, lights, and relative humidity. Tracking EC and run-off will allow you to determine when to increase your coco watering frequency.

Increase Frequency During Flowering:

The plant's water needs increase during flowering and your coco watering frequency should increase as well. You should plan to increase to 3-5 times per day. The specific frequency for your grow depends primarily on container size. If you use larger containers you can reduce your frequency to only twice per day. However, in coco, the best results come from small containers with more frequent watering. Three to five times per day may sound like a lot of water, but with such frequent watering the amounts required at each event are very small.

Coco Watering Schedule:

This coco watering schedule is designed to help you set the timing of multiple daily watering events. For timing the events, one hour of “lights on” is equivalent to two hours of “lights off”. Timing for these events works best as I describe below.

Light Cycles and Coco Watering Schedule:

Your coco watering schedule depends on the light schedule that you are using. In the cannabis community, light timing is expressed as a fraction with “Lights on” time over “Lights off” time.

  • 24/0: Lights are on 24 hours and off 0 hours
  • 18/6: Lights are on 18 hours and off 6 hours
  • 12/12: Lights are on 12 hours and off 12 hours. 12/12 timing is used during the flowering period with Photoperiod plants.

How to Handle Run-Off

When you are watering coco, each event should produce 10-20% run-off. This section of the coco watering guide, explains what you should do with it.

Remove Run-Off Quickly

As run-off emerges from the bottom of the pots, it should be removed as quickly as possible. If pots are allowed to sit in their own run-off, the water will reabsorb into the coco. When this happens, salts will accumulate in your coco and quickly burn your plants.

I recommend using plant elevators to raise the pots within the saucer. This prevents the re-absorption of run-off and increases drainage and airflow. To remove the waste water from the saucers, I strongly recommend elevating them and installing drain lines. We have complete plans and instructions for making “DIY Self-Draining Saucers”.

Measure the EC of the Run-off

Measuring and responding to run-off EC is the key to manage your grow like a pro. Reliable meters are available for as little as $10-$20. I use this Hone Forest EC meter and I have verified it’s accuracy against other meters. The technology involved is simple, so you do not need to invest in an expensive EC meter.

To know how to respond to run-off EC numbers, be sure to read our tutorial “How to Manage Run-off EC”.

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Author: Dr Coco

I am a university professor and have taught courses in horticulture. I am coco for cannabis and I hope you are coco for cannabis too :) Grower Love!