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You may have heard all the buzz surrounding coco coir and its new role in horticulture. Many are finding success using coco coir as a soilless growing medium in hydroponic systems, and home gardeners and farmers are catching on. Coco coir is starting to rival peat moss as a favorite growing medium for our treasured seeds and seedlings.
With the current environmental debate concerning the sustainability of peat moss, now is the time to consider coco coir as a sustainable alternative to peat moss.
Coco coir’s superior moisture-holding capacity, aeration, and antifungal properties make the coconut byproduct an excellent choice for seed starting. With the proper additives to improve nutrition, coco coir can be the foundation for healthy seedlings.
What is coco coir?
Coco coir is a byproduct of the coconut industry. Coir comes in three types – coco pith, also called coco peat, has a similar consistency and texture to peat moss. It’s a very absorbent medium and is excellent for seed starting, so long as it is mixed with something else to improve drainage and aeration.
Coir fiber has a somewhat stringy texture and is an excellent medium for potting soil. Coir fiber’s fibrous consistency allows for good aeration but isn’t fine enough for seed-starting mixes.
Coco chips resemble wood chips and are a chunkier coconut byproduct. Coco chips serve a similar purpose as pine bark in potting soil mix – the large pieces create air pockets that create drainage and aeration.
Advantages of using coco coir
The increased attention around coco coir has motivated some interesting studies about the coconut byproduct. What follows are several proven advantages to using coir over peat moss.
The primary reason that many gardeners are turning to coco coir is from a sustainability standpoint. Peat moss, a favorite of gardeners worldwide, is a diminishing resource. Sphagnum peat moss is formed over thousands of years in Canadian bogs. Unfortunately, peat moss is being harvested from the bogs faster than nature can replenish it.
Eventually, peat sources will run out and gardeners will have to find an alternative potting soil medium. By choosing to purchase coco coir, you are taking action to protect the world’s natural resources while simultaneously upcycling a waste product.
Sterile growing medium and neutral pH
Because of the way coco coir is processed, it is a sterilized medium. Whereas some potting mixes containing peat and compost may contain fungal spores or bad bacteria, coir doesn’t carry these potential problems. Coco coir naturally has antifungal properties, which is helpful in protecting seedlings from damping off.
According to coir.com, coir’s pH level is essentially neutral:
Unlike traditional acidic peat moss with a pH of 3.8-4.0, coir’s neutral pH of 5.5-6.8, makes it an ideal accompaniment to garden beds, containers, and greenhouses. Since most vegetables prefer a pH anywhere between 5.0-7.0, coir makes an ideal medium that won’t interfere with and may balance pH.²coir.com
A neutral pH s ideal for many seedlings. But for those gardeners who want to experiment, coir’s pH level can be easily adjusted. Simply add compost or soil sulfur to acidify the coir, or add lime to make the coir slightly alkaline, depending on the specific needs of your plants.
More forgiving of watering issues
Many gardeners have found that coco coir is more forgiving of watering issues than peat-based potting mixes. HortGrow has stated that coir holds 10 times its weight in water, meaning that plants growing in coco coir need to be watered less frequently¹. Overwatered coir is also less likely than peat to result in seedlings damping-off.
Disadvantages of using coco coir
With everything, it’s a matter of weighing the pros and cons. There are many benefits of using coco coir for seed-starting, but there are a few disadvantages as well.
There’s no way around it – coco coir is more expensive than peat moss. Like most sustainable alternatives, you may pay a little more for doing a good service to the environment. The cheapest way to buy coir is to buy in bulk – so consider going in on a few bales of coco coir with your gardener friends to save money on this excellent growing medium.
Coco coir has no nutritional value – it’s made from the middle, fibrous part of the coconut, which doesn’t contain any minerals or nutrients. While coir’s composition makes for a sterile growing medium, that also means that gardeners must add the amendments that plants need.
For seed starting, the low nutritional content isn’t so much an issue – seeds don’t need to be fertilized initially, as the seed already contains all the nutrition it needs to sprout. But this does mean that seedlings started in coco coir can’t stay in coir very long before they need to be transplanted or fertilized.
Seedlings left too long in coir will be leggy and show signs of a nutrient deficiency through yellowing of leaves. Malnourished seedlings will have a weaker root system, so either transplant seedlings using a different potting soil mix or apply a balanced fertilizer at the cotyledon stage to boost seedling health.
Coconuts are usually rinsed in saltwater as part of their processing. As a result, most coco coir has a high salt content. Be sure to rinse coir several times in water to wash away the salt before using coir to start seeds. Salt interferes with the roots’ ability to absorb water and nutrients like calcium, magnesium, and iron, which could be detrimental for your vulnerable seedlings.
How to start seeds in coco coir
Starting seeds in coco coir is essentially the same as starting seeds in a peat-based seed-starting mix. There are a few minor differences worthy of note.
Hydrate the coco coir
Coco coir, like peat moss, needs to be hydrated prior to use. Unlike peat moss, coco coir is not hydrophobic, so rehydrating bales of coir is relatively easy. Simply put a bale of coco coir, or a piece of a bale, in a large container and add water. Stir and fluff the coir until the mixture is universally moist. The coir doesn’t need to be dripping or soggy–if it is overhydrated, simply transfer the coir to a container that allows it to drain.
Fertilize your seedlings
Coco coir has no nutritional value, so seedlings will eventually need to be fertilized to promote healthy growth. Wait until seedlings are past the cotyledon stage and have developed their first set of true leaves. Fertilize seedlings any earlier and they likely won’t be able to metabolize all the nutrients they’re receiving.
Coco coir recipes
As more gardeners are choosing to use coco coir in place of peat moss, more coir “recipes” are becoming available. University extension offices are great resources for everything from seed-starting mixes, to potting soil mixes specific to vegetables.
A general rule of thumb for making seed-starting mix from scratch is to use some combination of coco coir, compost, perlite or vermiculite, and trace minerals or a balanced fertilizer. University of Oregon horticulturalist Brooke Edmonds recommends
- 1 part coco coir
- 1 part compost
- 1 part sand, vermiculite, or perlite³
Hydrate coir and mix with the compost and other ingredients.
For seed starting
Finer-textured coco pith, or coco peat, is just perfect for starting seeds. Its moisture-holding capabilities and lightweight consistency allow seeds to have the moisture and sunlight that is often required for germination.
For better drainage
Seeds require constant moisture to germinate, but once the seeds sprout, you’ll want to back off on the watering. Coco coir is known to hold moisture, so add perlite, a volcanic rock that improves drainage and aeration. A cheaper option to perlite is coarse sand.
For better nutrition
Eventually, your seeds will sprout and produce beautiful seedlings. To keep these seedlings happy and healthy, they are going to need a nutritional boost, as coco coir doesn’t have any minerals or nutrients available for absorption. When seedlings have grown their first set of true leaves, they are ready to be treated with a balanced fertilizer and a healthy serving of compost.
If you’re one of those gardeners who like to have a little more control in your garden, make your own fertilizer blend to use in your coir-based mixes. A common recipe is to use equal parts rock phosphate, greensand, bone meal, and kelp extract to add essential nutrients. This fertilizer blend won’t be water-soluble, so you’ll need to mix it in with the coco coir for the plants to be able to absorb it.
If you are striving to be a more environmentally conscious gardener, then it may be time to start using coco coir in place of peat moss. Coco coir in its various forms is an excellent substitute for peat in seed-starting mixes and potting soil mixes. With the addition of a few amendments to improve nutrition and drainage, coir is an excellent growing medium for seed-starting.
¹ HortGrow Solutions, “The Expert Way to Hydrate Coco Peat,” www.hortgrow.com, Oct 20, 2018. https://hortgrow.com/blogs/blog/the-expert-way-to-hydrate-coco-peat
² Coir.com, “Best pH for Coco Coir When Growing Vegetables,” www.coir.com,
³ Kym Pokorny, “Set seeds on the right path with homemade planting,” www.oregonstate.edu, Jan 17, 2020, “https://today.oregonstate.edu/news/set-seeds-right-path-homemade-planting-medium
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