Once mastered, growing plants in coco bricks is rewarding for hobby growers who value the quality and taste of fresh, home-grown produce with maximum harvest weights. Here are some tips to get you started.
Preparing Coco Bricks
Before using coco bricks, you must expand them by soaking them in a wheelbarrow, bucket or tub. Once the bricks have expanded, it’s a good idea to flush out the medium in case there is any salt remaining in them, unless you have purchased a pre-washed and buffered coco growing medium. Once you have expanded the bricks, let them dry out. You can do this in your growroom—simply spread the bricks on a tarp and turn your lights on.
If you have a lot of potting media to mix, I recommend using a cement mixer. To help with aeration, I add perlite, but it also needs to be washed before using. You may need to increase the ratio of coco-to-perlite to help retain more moisture. In my mixes, I like to use 50% coco, 30% perlite and 20% vermicompost. The more perlite added into the ratio, the quicker it will dry.
You can increase the percentage of coco in your mix to help retain water, or you could add more perlite to decrease water retention. If you are growing in large pots, try adding some worms into the medium with the vermicompost. Adding an inch of perlite on the bottom of the container and an inch on the top of your medium is also a good idea.
Watering and Feeding
Coco bricks hold a lot of water and salt, so big pots can create issues with overwatering and EC toxicities. Frequent dry periods are important to ensure optimal growth rates. This can be achieved by using a run-to-waste system and growing in shallow, rectangle-shaped pots. In a run-to-waste system, once you have your irrigation system calibrated, the growth rate is excellent.
A digital timer will help you achieve the correct watering intervals. Try flooding the grow medium for one minute, then irrigating with 10% of the runoff from the pots for the vegetative stage, and 20% of the runoff for the flowering stage.
Another option is to set up a gravity-feeding watering system set on a constant slow drip. Hand watering works as well, although this method won’t allow you to achieve the frequent wet/dry periods needed to optimize growth.
If it’s really hot outside, this may affect your indoor garden if you don’t have an effective cooling system. Plants require more water than food in hot temperatures, just like humans. In this situation, make up your plant food mix in a 2-L ice cream container, then freeze it for 24 hours. Drop the entire frozen ice block into your reservoir filled with pure water so the food can be accessed slowly.
When growing with coco, a pH of 6 in the vegetative stage and 5.8 in the flowering stage is optimal and tap water quality is important. If you cannot find a source of clean or soft-to-medium water, you should mix RO water with your hard water to make it softer. The ideal EC of your water is between 0.2 and 0.6.
EC Toxicity Troubleshooting
The key to success with coco growing is to monitor EC levels in the growing medium, as salt buildup is a common problem. You can get a meter that measures EC from your local retail shop. Try feeding followed by water in a continuous cycle to keep EC levels down, otherwise flushing is necessary.
Flushing needs to be done four weeks into the vegetative stage at the very latest, or immediately when an EC toxicity is detected. To flush the medium in a run-to-waste system, if pots are not too heavy, you can carry them to the bathroom and run water through them until the EC reads neutral. Using free-draining pots makes this process easier.
Doing a Core Sample Analysis
The EC of the runoff water in your run-to-waste tank does not accurately measure the EC levels in your growing medium. You must do a core sample analysis to figure out what’s going on in the grow medium itself. To do a core sample to determine your medium’s EC levels:
- Punch deep into the center of pots where the roots are most abundant and take material from several areas around the pot to get an average sample. Don’t worry about breaking a few roots here and there. You can use a trowel, fork or spoon if necessary.
- Take a handful of the growing medium and place it in a small bowl.
- Irrigate the sample with small amounts of demineralized water until it is wet enough that, when squeezed in your hand, it has excess runoff.
- Fill a measuring cup with demineralized water to 5 fl. oz.
- Add your core sample of media to the water so the level in the measuring cup reaches 8 fl. oz.
- Stir and allow to sit for two hours.
- After the two hours are up, stir again and use a strainer to filter the liquid from the solid into a separate container.
- Once this is done, you can check the EC and pH of the media to determine what is actually happening in the root zone. This will allow you to correct your feeding strengths and pH levels if they are too high or too low.
- Backfill the hole you made in your medium with pure worm castings.
If you’re experimenting with organic additives, coco is a good medium to use, as it is a natural material. Here are a few options I’ve been experimenting with:
- Using fish tank water alongside your usual feed schedule provides essential nitrates and other nutrients for plant growth. Plan for about three goldfish per plant and the appearance, taste and yield size of your produce will increase. If you have the resources, an aquaculture system will provide you with fish to eat while you grow organic produce.
- Pulverized, acidic volcanic rock can provide essential macro- and micronutrients for your plants.
- Seaweed extracts provide a range of micronutrients and beneficial elements to plants, and can be easily hand-watered into your feeding schedule.
- Try this unique, organic fertilizer when plants are first flowering: run about 7 lbs. of potatoes through a grater, squeeze all the juice out and separate it from the pulp. Throw the pulp in the compost. The liquid is a powerful bloom fertilizer.
- Another great additive for plants in the bloom stage is fresh fish blood added directly into your reservoir.
- In the final two weeks of flowering, feed the plant nothing but water, although flushing with a molasses solution can provide some organic nutrition.
It’s now time to sit back and enjoy high-quality, bountiful harvests!