Despite the importance of grow media to a garden, few growers think much about grow media storage.
The most important point, regardless of media type, is to keep grow media dry and free from contaminants. But many factors contribute to keeping media protected and safe for your plants.
Let’s look at considerations for storing grow media based on media type.
Soilless mixes consist of a base media and usually additives such as pH adjusters or an initial nutrient charge. The two most common base components are peat moss and cococoir. Both need the same storage conditions: insulation from extreme heat and cold, and protection from spills and contamination. While the base itself does not go bad, per se, it may contain additives that can degrade over time.
- Peat moss typically has a recommended shelf life of six to 12 months.
- Coco coir-based media usually have a shorter recommended shelf life of three to nine months, depending on the manufacturer.
Inert grow media has no cation exchange capacity (CEC), meaning it is incapable of holding positively charged ions and does not bind nutrients for later use. These grow media have a long shelf life and are not usually subject to temperature, but they do need to be protected from spills and high humidity.
- Rockwool comes in many sizes and shapes that are shipped in different configurations. It can come as individually wrapped slabs, or cubes or bulk packed without wrapping. Wrapping offers partial protection against contamination, but not total.
- Perlite and vermiculite are common grow media that are typically sold in large bags. If the entire bag is not used at one time, be sure to securely tape-seal the remainder to prevent contamination.
Rock dust is commonly sold under names including glacial rock dust or Azomite. These products contain sources of magnesium and calcium; traces of potassium, cobalt and iron; and possibly many more micronutrients—depending on the source. Although rock dust typically does not need protection from heat or cold, it does need to be kept dry, as the fine powder clumps together when wet. Also, be sure to keep it away from contamination sources. Typically, these products have an unlimited shelf life when stored correctly.
Living grow media ingredients are finickier when it comes to storage conditions than other types of grow media. In addition to being kept dry and away from contaminants, the following components also need to be protected from extreme temperatures and humidity. They have a limited shelf life and need to be used before expiring.
- Root zone inoculants, such as fungi, bacteria and nematodes, will die in high temperatures and most need protection from freezing conditions as well.
- Earth worm castings, being a diverse colony of microorganisms, also need to be protected from extreme temperatures.
- Guanos will decay if exposed to high temperatures or humidity for long periods of time.
- Indoors in a clean, separate room from grow spaces is the ideal location to store grow media. Temperature and humidity can be controlled, and exposure to contamination can be minimized.
- Greenhouses are usually fine to store most growing media. Just make sure to store the media away from the rest of the grow to prevent possible cross-contamination.
- An outdoor shed is an option for storing inert grow media. Never put grow media that contains inoculants, nutrients or buffers into an outdoor shed, as they should not be exposed to extreme temperatures.
- Outdoors in direct sunlight is never a good option for any grow media. In addition to the heat exposure, everything from bugs to animals can get into the media.
Additional Tips for Grow Media Storage:
- Don’t buy too much grow media unless you have a suitable storage location available.
- Never store any grow media directly on the floor-ever. At a minimum, use a pallet. Remember, water spills/floods are inevitable in grow facilities.
- Immediately tape all tears in wrapping, boxes, etc., to prevent contamination.
- When in doubt with older grow media, contact the manufacturer to see if it is still good, or go with the old phrase, “When in doubt, toss it out.”
- Read the label. Most good soil-blending companies will indicate where and how long to store their products.
- Knowing your media’s source is critical since some grow media has an expiration date. Knowing how long it spent in transit to you is also important. Typically, manufacturers sell to distributors, who sell to retailers, who then sell to you-the customer. All commercial grow facilities that rely on perishable grow media would do well to develop direct relationships with the manufacturers when possible. This will eliminate holding times at distributors and guarantee the freshest products possible.
Christopher Sloper is a self-proclaimed gardening geek both indoors and out. From corn to cannabis, he has grown it all-for decades. His education consists of a Bachelor of Science in Chemistry and a Master of Business Administration. Not only can he grow, but can market, sell and strategize. He’s the CEO of Technical Gardener Inc., a full-service horticultural consulting firm and the author of “The LED Grow Book,” now in its second edition.
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Mycorrhizae seems to be a very important additive for cultivators, as nearly two-thirds (64%) indicate they incorporate it into their growing media. Other top additives-although all used by less than one-quarter of respondents-include lime, fertilizer starter charge and controlled release fertilizer. Nineteen percent utilize wetting agents, and 8% use water-absorbing gels.
What cultivators pay for their growing media is just as diverse as the types of media they utilize in their facilities. Seven percent say they don’t spend anything on growing media annually-perhaps some of those respondents rely on field soil, and others indicated they grow aeroponically (without any media). Just over one-third of cultivators spend a bit more ($4,999 or less). Growers who spend between $10,000 to $19,999 total 15% of respondents; and 10% of respondents shell out more than $100,000 annually on their growing media.
The three top growing media challenges among research participants include: shipping/freight costs (22%), receiving inconsistent product from manufacturers (20%), and determining correct nutrient mix/supplementation (15%).
Growing Media Quick Tips
Survey participants shared quick tips about how to best optimize your media’s use.
“Store data, keep track of every detail.”– Tim Schimmel, Kind Farms
“Make sure not to overfertilize, which leads to nutrient lockout.”– Scott Holland, Willow Industries (formerly Durango Organics)
“Get to know your manufacturer and the processes they used.”– Preferred to remain anonymous
“Educate yourself on how to control your medium’s air/water ratio and prevent salt build-up.”– Cody Fasbinder, Urban Greenhouse
“Manage media pH/EC levels through testing and manipulating feeding schedules.”– Preferred to remain anonymous
“Dialing in the correct amount of time that soaks the grow media to maximize the time between feedings is key.– Jerome Jabson, Natural Green ReLeaf
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Cultivators across the board understand that the media in which their cannabis grows is much more than a plant holder. It’s the vessel in which roots take in essential nutrients and ever-so-important H2O. In other words, media is a vital component to plant health.
However, it’s noteworthy to mention that media is not a one-size-fits-all growing element. Depending on your operation’s goals, budgets and environment, the right growing media for you may differ from your fellow cultivators. Maybe you’ve found rockwool to be your go-to option, or you’re experimenting with hydroton (hydroponic grow rocks), or even learning that a mix of peat in combination with other media types has proven to be your plants’ best bet for high quality. Perhaps you want a media option that can be recycled in your grow, or peace of mind by starting fresh with new product at the beginning of every plant cycle.
But even beyond that crucial product selection, you may also find uniqueness in the challenges you face, from understanding the media additives required to keep nutrients and pH at desired levels, to ensuring there’s enough aeration in your media to keep excess moisture at bay.
To shed light on these topics and more, Cannabis Business Times studied readers’ media preferences and practices for this first-of-its-kind “Growing Media Guide.” In this report, we share how cultivators purchase and think about their growing media. We’ve also recruited cultivators and plant experts to share important considerations when making media selections, growing media tips relating to care and storage, and more.
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While options abound when it comes to media selection, the majority of cultivators who participated in the study (72%) use just one to two mixes throughout their grows. Twenty-two percent work with three or four media options, and about 7% use five mixes or more in their cultivation operations.
Less commonality exists among growers’ buying practices. While nearly half (47%) say they purchase standard mixes from growing media manufacturers, many cultivators prepare custom mixes either in conjunction with their manufacturer, or in house. One-quarter of respondents implement manufactured mixes as well as their own in-house mixes. Cultivators who rely solely on their own growing media mixes in house comprised 19% of our research sample.
As far as where cultivators obtain their growing media of choice, most purchase directly from a growing media manufacturer (41%) or from a local retailer (42%), and 18% rely on a regional distributor to supply their mixes.
And regarding locations from where peat is sourced, 34% of cultivators choose peat from the U.S. Just under a quarter of respondents said they source their peat from Canada, and 5% have their peat shipped in from Europe. However, 36% of cultivators report that they aren’t sure where their peat is manufactured, so those numbers could fluctuate with more information.
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