Which Growing Medium Should I Choose?

COCO COIR – most suitable for: container gardening • drip systems • raised beds

Coco coir is made from the husk of a coconut. Coco can vary in appearance and type and may be purchased as pith, fibers or chips. Each coco blend varies from manufacturer to manufacturer. It may be heavy in fibers, light in fibers, contain chips, contain no chips, etc. Coco may just be the most forgiving grow media out there. Like soil, it acts as a filter for nutrients – this useful feature helps restrict nutrient burn to your plants. Additionally, coco coir has excellent water retention properties allowing you flexibility in your watering schedule. It holds on to water allowing a buffer if you forget to water your plants one day, but at the same time, coco makes it difficult to over-water your plants. Unlike potting soil, coco has a sponge-like quality that discourages compaction. It also has a great oxygen to water ratio and is naturally pH neutral. When choosing a brand of coco, you will want to look one that has been properly buffered and rinsed. Coco is known to bond with specific minerals and manufacturers have offset this with rigorous washing and buffering processes. When mixed with perlite, Hydroton or Growstones, coco is a preferred media.

ROCKWOOL – most suitable for: all types of gardening and hydroponic techniques

Over the years, rockwool has been a favorite growing media of many gardeners. Because of its clean, sustainable and easy-to-use qualities, rockwool is widely used in commercial hydroponics. It usually comes in the form of a block, but can also be found in bales and small cubes. Rockwool has a high water absorption capability, but like coco coir has great oxygen to water ratio – this helps keep plant roots happy and thriving. Rockwool can work as an aeration amendment to soil and has become a popular choice for soil or peat gardeners. Generally you do not want to re-use rockwool.

PERLITE – most suitable for: amending soil or coco

Perlite should not be used as a standalone grow media, but it is a wonderful media amendment. When blended with soil or coco, perlite provides excellent media aeration, does not affect water retention and helps to keep soil from compressing as it breaks down.

CLAY PEBBLES (HYDROTON™) – most suitable for: amending soil or coco • NFT systems • flood & drain systems • aeroponics • aquaponics

Clay pebbles (or Hydroton™) can be used as a standalone media or as an amendment to coco or soil. Because clay pebbles are easy to clean and re-use, they are popular among hydroponic growers. Similar to perlite, clay pebbles do not hold water well, therefore the use of clay pebbles allows gardeners who want to create an aggressive feeding schedule water as often as they like. Because of their low water retention, clay pebbles also act as a great media aerator while not affecting media moisture levels. While there are advantages to the low water holding capacity of clay pebbles, this may also be their biggest fallback. If for some reason, your pump fails and your plants don’t get watered, they are likely to be dead in a short time. It is wise to monitor your watering systems when using clay pebbles to avoid under-watering your plants.

SOIL – most suitable for: container gardening • drip systems • raised beds

Soil is the most common and most familiar growing media to both the hobbyist and professional grower. Potting soil tends to be the most affordable and easy to use. It can also create a great support system for large plants when planted in a suitable container with a premium blend. Not all soil or potting mixes are created equal. When shopping for
a potting soil, you want to consider factors such as aeration, fertilizer content, amendments, etc. The majority of the potting soils available are peat-based soils. Peat is not necessarily the best standalone grow media, but when mixed with quality amendments and charged with nutrients, it can be a good choice. Keep in mind that peat tends to break down and will compact, not allowing for adequate drainage. This will create a favorable environment for harmful pathogens and can restrict oxygen availability to plant roots. You want to look for a mix that is blended with perlite or some other amendment to help create a good oxygen to water ratio. You will also want to look at what fertilizers are mixed into the potting soil. Most added fertilizers and organic additives will be time released and should last you a few weeks. It is important to look at the manufacturer’s recommendations on when to start fertilizing your plants. If you choose to use a potting soil that contains only a few additives, there are several quality dry amendments available. Many potting mixes are pre-mixed with fertilizers and organic additives and are ready to use out of the bag. Pre-mixed blends will typically still require supplemental fertilization after the first few weeks. You want to be careful not to over water your soil. Overwatering can be detrimental to your plants. Even though the soil on the top of the container appears dry, it does not necessarily mean that it is time to water. To check for adequate moisture, lift up your container to check the weight – a heavier container can be a good indicator of moist soil. If you are still unsure, you can check the deeper soil with your finger or you can purchase a moisture meter at almost any garden store.