Growing Marijuana in Coco Coir: Insider Secrets

Coco coir is a popular root zone media choice for growing marijuana. It can be easy to use, and some growers use it for more than one crop, which saves money. But it can sometimes cause problems for your marijuana plants—harming growth rate, potency, yield and your bank account—until you master these important coco coir facts…

Marijuana Coco Coir Fact #1: Coco Coir Manufacturing Standards

As with manufacturers of gardening soil, soilless mix, and rockwool, there are multiple coco coir manufacturers—and only a few make quality grow op products. Coco coir comes from coconut husks. The quality of the coco coir depends a lot on where and how the husks are sourced. The quality and age of the husks are also important. Some coconut husks are loaded with sodium and toxic contaminants from ocean water or storage ponds. Other husks are too green and immature to be processed into quality horticultural material.

When coconut husks aren’t processed properly by washing them with fresh water at the right temperatures and for long enough, and by carefully treating and drying the material after washing, the resultant coco coir can cause nutrients problems that harm or kill your plants.

What’s more, coconut husks have to be expertly processed so they break down into “coco peat” fibers with the right water-holding, aeration, internal consistency, and durability for marijuana plants. The processing must be done using professional facilities, methods, and materials. If not, you see inferior coir that tends to become waterlogged or break down quickly, leading to drowning marijuana roots.

During horticultural coco coir media manufacturing, husks and fibers must be washed and treated correctly or the finished product can cause unsolvable nutrients problems involving nitrogen, calcium, iron, magnesium, potassium, sodium, and chlorine.

And coco coir must also be graded, packaged, shipped and stored correctly so it works well for your marijuana garden.

You’re probably wondering what’s the best coco coir brand. I’ve tested all major brands and many off-label brands, and have experienced intermittent or pervasive problems with all of them, including Canna and Botanicare. It doesn’t help that there are significant variations in coco coir quality batch to batch, even from the same manufacturer.

Ask your hydroponics store what brands of coco coir they most recommend. But no matter what they recommend, take a look at this next fact…

Marijuana Coco Coir Fact #2: Wash & Test Coco Coir

No matter what a hydroponics store or coco coir manufacturer tells you about the quality, pre-washing, processing, and usefulness of their coco coir product, it’s best to wash and test it yourself before you use it. What I do is buy the smallest amounts possible of the top two coco coir brands recommended by my hydroponics store. Then I test the products using the following method:

  • Put the coco coir in a two-gallon bucket that has holes in the bottom, and place that bucket inside a five-gallon bucket.
  • Using reverse osmosis water, pour 2.5 gallons of water at pH 5.7-5.9 through the coco coir, collecting the runoff water in the five-gallon bucket.
  • Test the parts per million and pH of the runoff water.
  • If the parts per million reading is higher than 450 ppm, and/or the pH is wildly out of range, repeat the experiment to see if you can get runoff water that’s less than 450 ppm and within pH range.
  • If you rinse your coco coir more than three times and it’s still showing 450 or more ppm, and/or the pH is out of range, don’t use that coco coir.
  • This rinsing and monitoring process take times and you may go through several brands of coco coir before you find a quality product. When I rinse coco coir and the runoff pH is within range and the runoff parts per million is below 300, I feel I can trust that coco coir.

However, because batch quality varies, as soon as you find a test amount of coco coir that has low runoff parts per million and acceptable runoff pH, go back to the supplier and buy a lot more of that product if the storeowner tells you the batch he has now is the same batch as the coir that tested well. If it isn’t, you’ll have to test the new batch.

Marijuana Coco Coir Fact #3:  Buying the Best Form of Coco Coir

Beyond finding properly-manufactured coco coir that performs well in runoff pH and ppm tests, you want to buy coco coir that has the right consistency and configuration. Coco coir comes in a variety of configurations, including condensed bricks, loose fiber, coco peat blocks, and coco coir fibers mixed with perlite.

The best way to grade coco coir’s usefulness in your grow op is to wash and measure it, and to physically handle and visually examine it. You’re looking for dark, clean, golden-brown fibers with the consistency of moderately-dry soil. The coco shouldn’t have clumps or fine powder.

Many marijuana coco coir growers use coco in raised grow tables for sea of green marijuana gardening while others uses it in individual pots. I don’t pay the extra price for coco coir that comes with perlite, but especially if I’m growing in a grow room that tends towards high humidity, I might cut the coco with 10% coarse perlite. Bricked coco is usually cheaper, but harder to work with. I suggest loose fiber.

And again please remember to first buy a small amount, so you can thoroughly inspect the coco before you buy the larger amount you’ll use for your season if you find that the coir is high quality.

Marijuana Coco Coir Growing Fact #4: Watering Coco Coir

Coco coir retains water well—too well if you’re a marijuana grower who tends to overwater. On top of that, coco coir’s appearance isn’t a reliable way of knowing when it needs more water. Coco coir should be watered when it’s 50-70% dry. But how can you determine the dryness of your coco coir?

One method works only if you’re growing in individual pots:

  • Water until about 15-20% of the water runs out the bottom of the pots and the coir appears to be thoroughly wet.
  • Weigh the pots and record their weight. If they’re evenly watered, they’ll all weigh about the same.
  • When you think 50-70% of the moisture has left the coco coir root zone, weigh the pots again.
  • The difference between the initial wet weight and the current weight is used in a percentage calculation to determine how dry the coco has become.

If you’re growing in a grow table or don’t want to weigh pots, get a tensiometer. A tensiometer is the only root zone media moisture measuring device that really works. Most soil moisture meters don’t. A tensiometer accurately measures soil water tension, which tells you the effort required by your marijuana roots to extract water from your root zone media.

Tensiometers are relatively inexpensive and can be used in coco coir, soil, soilless mix, and other root zone media. Take a look at these instructions for using tensiometers in agriculture. There is a learning curve, but you’ll be glad you’re using a tensiometer.

Two other things to know: Coco coir is particularly sensitive to salts and contaminants, because it has chemical and physical properties that interact with water and whatever’s in it in ways that no other marijuana root zone media does, so always use reverse osmosis water.

Please be careful not to overwater. Coco coir is like a sponge. Too many coco coir users drown their cannabis roots, which is especially bad for tender seedlings and clones that don’t yet have fully-formed root systems.

Marijuana Coco Coir Growing Fact #5:

Use Marijuana Coco Coir Nutrients

If you use regular hydroponics nutrients or organic nutrients with coco coir, you’ll almost certainly see crop problems. I used to hate coco coir, until someone explained to me that it was the fertilizers I was using, not just the coir, that caused the problems.

Fortunately, one hydroponics nutrients company employed its team of plant scientists, soil scientists, chemists, and professional hydroponics growers to intensely study coco coir and design and manufacture the only hydroponics nutrients feed program that consistently works well in marijuana coco coir gardens.

Growers using other nutrients brands see growth, yield, and potency problems, especially because coco coir tends to lock out magnesium and calcium crucial for photosynthesis and bud development in bloom phase.

I finally discovered that Advanced Nutrients Sensi Coco and Connoisseur Coco pH Perfect coco coir base nutrient work best in my coco coir grow ops. One reason is these are the only base nutrients that contain sufficient pH buffering and other features that eliminate problems cannabis growers experience with all other nutrients brands in coco coir.

Before Sensi and Connoisseur pH Perfect coco coir base nutrients became available, growers struggled with bizarre nutrients-related plant problems, forced to use cal-mag supplements that created more problems than they solved. Growers also harmed their marijuana plants with repeated flushing, trying different nutrients parts per million concentrations, underwatering, and overwatering.

According to the manufacturer, the Sensi and Connoisseur coco coir base nutrients eliminate coco grower problems because they contain the proper forms, ratios and amounts of calcium, magnesium, iron, and potassium for coco coir.

Another reason marijuana coco coir growers get faster-growing plants and bigger, more potent buds when they use Advanced Nutrients coco coir hydroponics base nutrients is that pH Perfect formulas automatically balance your nutrients water and root zone to the ideal 5.7 pH so your cannabis plants easily absorb all the nutrients elements they need.

High-yielding bloom boosters and other products in the Advanced Nutrients line-up are fully compatible with Sensi and Connoisseur coco base nutrients.

If you’re not using coco coir because you tried it and had nutrients issues or overwatering problems, or because you’re satisfied with the marijuana root zone media you’re already using, you can use Advanced Nutrients coco-specific fertilizers and quality coco to get the following benefits:

  • Coco coir holds water well, so you water less, and less frequently.
  • Coco coir is an ideal host material for beneficial, root-enhancing microbes.
  • Coco coir can sometimes be recycled for use in multiple crop cycles. Use Sensizym to cleanse coco coir of organic root zone debris so the coco can be safely reused.
  • Coco coir’s favorable oxygen/water ratios provide more oxygen to roots and prevent waterlogging (as long as watering is done properly) which increases growth rate and bud yield.
  • Coco coir is a mostly-inert medium that works well with hydroponics and organic nutrients. If you want to grow organically using coco coir, use Iguana Juice and other organic supplements—they’re made specifically for cannabis and work well in coco.

There are many marijuana growers who won’t use anything other than coco coir. For them, and for anyone who hasn’t yet used coco, mastering the facts in this article guarantee you’ll be harvesting big, sticky yields from your marijuana coco coir garden.