TL;DR:

The Ironhead method has proven to be one of the best schedules of coco coir nutrients for growing marijuana, for its fast growth rates, no deficiencies and high yields. Based on General Hydroponics Micro, Bloom and Cali-Magic this guide will walk you through the setup required and feeding schedule for the optimal way to grow marijuana in coco coir.

Best Nutrients for Coco Coir - Ironhead Method

The Ironhead Method is an advanced feeding method designed for growing cannabis in coco coir. Initially posted in 2015 on Grasscity and updated in 2016, the Ironhead Method was created based off the Lucas Method for growing in hydroponics and the work done by GratefulH3ad for growing in coco coir. Since 2015, the Ironhead method has gained a lot of popularity, and has become a leading method for growing Cannabis in coco coir.

If your plant is still in the seedling stage, check out the 5 steps to get growing in the seedling stage article.

Materials

Pots

The standard for soil and coco coir grows are fabric pots, because they help to aerate the root system, they are convenient to ship and they are easy to store. Here is an example of what you might want.

When growing with coco coir, you want to aim for 10% runoff each watering. You also want to make sure the plant is never sitting in runoff. This is generally whats used to avoid your plant from sitting in its runoff.

Coco Coir Mix

Ironhead suggests a mix of 50/50 coco coir to perlite.

• When buying coco coir, there are many things to consider - what the manufacturing conditions were like, whether its been washed, whether its been pre-treated with cal/mag etc. The summary is, the gold standard for coco coir is Canna, where you can buy dehydrated coir bricks or bags. They are high quality, and all you need to do to add nutrient solution and start growing - no need to wash, pre-treat etc. If you are want to save some money and buy a cheaper coco coir, make sure to follow these instructions on how to wash and buffer coco coir.
• When buying the perlite, you should get one without any added nutrients. Often times, perlite without added nutrients is sold as “organic”. Here is a good choice for perlite without added nutrients.

Getting growing

Starting seeds and seedlings (weeks 0-2)

To get started with your seeds, see our article for tips on germinating cannabis seeds. A classic way to transplant seedlings after they’ve germinated is using plastic solo cups with holes cut in the bottoms to allow for drainage, though any small pot will work. Ironhead says he only “bottom feeds” the plants until they have 3-4 sets of leaves. By this he means place the cups/pots in a tote and fill the tote with nutrient solution. In my experience this isn’t completely necessary, but while watering you just need to be careful with young plants. You should start the plant with full strength vegetation nutrient solution.

Vegetation (weeks 2-5)

Feed once per day, and aim for 10-20% runoff per feeding. Its easiest to make a large batch of nutrients (like 5 gallons at a time) to make watering each day quick and easy.

Base Nutrients

• General Hydroponics Micro 6 mL/gal
• General Hydroponics Bloom 9 mL/gal
• General Hydroponics Cali-Magic 1.5 mL/gal

Supplementary Products

• House & Gardens Drip Clean 1 mL/gal
• (Optional) SM-90 5 mL/gal - Nutrilife pulled this from shelves, and its very difficult to get now. You won’t have any problems if you don’t have this. Hydroguard is a good alternative, that will accomplish a roughly similar effect.

After 3-4 sets of leaves

• (Optional) Root Excelerator 1mL/gal
• (Optional) Photosynthesis Plus 7.5mL/gal

Flowering (weeks 5-10)

Same as before, feed once per day and aim for 10-20% runoff per feeding. Its easiest to make a large batch of nutrients (like 5 gallons at a time) to make watering each day quick and easy.

In flowering, the base nutrient levels are adjusted and additional products are added to enhance bud and terpene production. Being plain watering feedings every 3-4 days.

Base Nutrients

• General Hydroponics Micro 4 mL/gal
• General Hydroponics Bloom 10 mL/gal
• General Hydroponics Cali-Magic 1.5 mL/gal

Supplementary Products

• House & Gardens Drip Clean 1 mL/gal - Used to reduce salt build-up within the growing medium, and keep things flowing well.
• (Optional) SM-90 5 mL/gal - This is a “wetting agent’ which encourages new root growth, but also is good for combating bacteria and pests like Root Rot, Aphids, Thrips, Whiteflies, spider mites and White Powdery Mildew. Nutrilife pulled this from shelves, and its very difficult to get now. You won’t have any problems if you don’t use this. Hydroguard is a decent alternative, that will accomplish a roughly similar effect. The instructions on the bottle for Hydroguard are good enough - 2 mL/gal.
• (Optional) Photosynthesis Plus 7.5mL/gal 2 times a week - Contains healthy bacteria and fungi which will develop a symbiotic relationship with the root system of your plant. Is beneficial for your plant, but Hydroguard can also be used for this application.

Additional products for flowering specific

• Canna Cannazym 5mL/gal
  • Breaks down dead organic matter in the root zone, converting into nutrients the plant can use.
• General Hydroponics Floralicious 1mL/gal - This is a good bloom enhancer, but be sure not to get the Floralicious Plus because it provides too much Nitrogen for your plant.
• General Hydroponics FloraNectar 2.5mL/gal, 5mL/gal at week 4 - Contains sugars including molasses as well as Magnesium Sulfate. Enhances trichrome production.
• General Hydroponics KoolBloom 2mL/gal, on day 7 of flowering - Improves bud growth and weight (bulking formula).
• (Optional, debated) General Hydroponics FloraKleen 10mL/gal for last 2 weeks - There are many debates within forums whether a flushing with pure water (or FloraKleen) in the last 2 weeks is necessary. Some say it puts unnecessary stress on the plant towards the end of its life, and others say it flushes out the stored salts in the plant improving taste. Personally I would say if you do decide to flush, use normal pH balanced tap water instead of buying another product - but IronHead himself recommends FloraKleen!

FAQ

Q: Is Coco Coir better than soil?
A: If your goal is to produce the largest yields as fast as possible and dont mind the slight additional work and costs involved, yes coco coir is better than soil. If watering your plant daily, and mixing nutrients sounds like too much work, you are likely better off using plain soil.

Q: What are the best nutrients for Coco?
A: There are many formulas for growing plants using coco coir, primarily because most hydroponic formulas can be used with slight modifications. With that said, the Ironhead method is the best nutrition schedule we’ve found for growing marijuana in coco coir. Check out our guide for growing marijuana in coconut coir using the Ironhead formula.

Q: Which Coco Coir is best?
A: We always recommend Canna dehydrated bricks which is some of the highest quality coco - it comes pre washed and pre-buffered so you can start growing right away.