PittMoss has emerged as an alternative to peat moss as a growing medium and potting mix — and that’s great news for gardeners who wish to break their peat habit in favor of a sustainable product. Here to explain what PittMoss is, how it’s made, and the advantages of using recycled materials is Dr. Charles Bethke, a horticultural soil and nutrition consultant.
Charles is the director of research development for PittMoss, and back in the 1980s and ’90s, he worked in the same capacity at Michigan Peat Company. He grew up in the substrates and greenhouse growing business and got his start doing soil experiments in his dad’s greenhouse when he was 8 years old. He earned a bachelor’s degree in soil science and agronomics from Michigan State and a master’s in soil fertility from the University of Missouri-Columbia before returning home to work on the family farm. In time, he decided he liked the scientific side of the horticulture industry and went back to Michigan State for his Ph.D. in plant physiology and nutrition.
After obtaining his doctorate, Charles became the technical director for Michigan Peat Company, one of the largest peat harvesters and peat processors in the United States. Over the course of 14 years in that position, he saw more greenhouses than you could imagine and helped countless growers solve problems. Charles next became a consultant. He was at a trade show in 2014 when Mont Handley and Mark Goldman from PittMoss, knowing his reputation, came up to him to show off their fluffy gray product made from paper and cardboard.
“I saw that and I felt it, and I looked at it, and I said, ‘I wanna be involved in this,’ when they told the story,” he recalls. Now his job is to make sure PittMoss substrates work well for most gardeners.
Charles has come a long way from being 8 years old and experimenting with using sawdust in potting mix. It didn’t work well and he ruined the hardwood floor in his bedroom, but he learned then that nitrogen was needed to complement all the carbon in sawdust.
“I’m not a young chick, but I have a philosophy: ‘When you’re green, you grow. When you’re ripe, you rot.’ So every day we start something new, and we learn more, and by learning, by doing, we keep young,” Charles says. “And, of course, all gardeners are like that. Everybody knows that every year is a new start.
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Before proceeding any further with our discussion of PittMoss, I want to take a moment to remind you that I have a new book coming out this year, and it’s available for pre-order now. The title is “The Vegetable Gardening Book: Your complete guide to growing an edible organic garden from seed to harvest,” and I’m very excited for you to read it. It’s chock full of insider tips and new-to-you information that will help you step up your gardening game and tackle challenges.
The First, Second & Third Paradigms of Substrates
Substrate is the material that an organism grows on or gets its nourishment from. So in the case of a potted plant from a nursery, the substrate is potting mix. In hydroponic growing, popular substrates include stone wool, phenolic foam, coir (coconut fiber) and expanded clay pebbles. In mushroom farming, a few popular substrates are pasteurized straw, sawdust and manure.
The “first paradigm in substrates,” as Charles calls it, is to take garden soil, add materials to it to modify it, mix it up, and shovel it into pots. “That’s the way the world has worked for many, many years,” he says. “And then the discovery of Sphagnum peat as a substrate came about through actually some very creative work.”
Their research was sponsored by an attic insulation company, Zonolite, which made vermiculite and thought it had a future as a growing medium.
Charles says Sphagnum peat was a miserable product on its own because of its low pH — it is too acidic for most plants gardeners grow. Sphagnum peat also held too much water, he says, but in time developers learned to add lime to raise the pH and to add various nutrients and aggregates for a better product. “That was the second paradigm,” he says of the peat era.
Now comes the third paradigm: Using recycled and waste materials such as coir, pine bark, wood fiber and paper.
PittMoss, created by Mont Handley, uses waste paper and waste cardboard. Charles explains that Mont was a hobby gardener with a sensitivity toward the environment. Mont saw that paper and cardboard that was ending up in landfills could instead be used as substrate.
Mont began experimenting with paper about 30 years ago, trying many things, including putting paper in his mother’s blender and fiberizing it, Charles says. “He pursued the USDA to see if he could get some funding to demonstrate that it would work and that the glues on cardboard and inks on paper were all okay, and he got a fund for that. They did a bunch of research with tomatoes and demonstrated it was good, and he looked at about 20 different paper sources and glue sources, and it worked well.”
Mont called his product “New Peat,” and it didn’t develop into much — the idea just sat on the shelf for a while. Mont’s life moved on, but in retirement, he picked the idea back up again.
The name “PittMoss” came about because it is manufactured in Pittsburgh, Pennsylvania. It’s taken quite some time to get it off the ground, an effort that was boosted when Mont appeared on “Shark Tank,” the television show in which entrepreneurs pitch their products to celebrity investors.
How PittMoss Is Made
Natural fibers, or plant fibers, are known as lignocellulosic fibers in the science community. They contain cellulose and lignins.
PittMoss starts with “fiberizing” the lignocellulosic fibers in paper into small fibers that are then reagglomerated, or reformed. “Because they’re reformed, we can then structure the particles to outperform other things,” Charles says.
Unlike coir and peat, in which what you get is what you get, PittMoss can be engineered to meet the requirements of various applications.
PittMoss can control the internal porosity — the ability to hold air and water — of its different products. Controlling the particle size of PittMoss influences gas exchange and the amount of water that drains out.
“By the internal porosity and the external size of the particles, we then can create a good air-water management system for an application,” Charles says. “So that becomes critical to the different products we make.”
Some PittMoss products come raw, leaving it up to the customer to add nutrients, while others are fully nutrient balanced, such as PittMoss Plentiful, which contains compost, fish emulsion and poultry manure, and it contains microbial inoculum, which helps plants take up nutrients more effectively.
PittMoss is rich in labile carbon, which is carbon that is readily available to microbes to be turned into food and fuel.
PittMoss is environmentally compatible: It doesn’t leave behind white specks, pieces of plastic or toxins.
And lastly, Charles says PittMoss is designed to be aesthetically desirable, so consumers will want to put their hands in it and plant in it.
Choosing Paper and Cardboard for PittMoss
Paper, for the most part, is clean and pesticide-free, even more so than peat moss, Charles says. Peat moss is out in the open and gets dust and pesticides that are carried in the air. But paper and cardboard come from the inside of trees. Paper processing is very clean these days and the ink used is primarily soy-based. “There’s a lot of standards by the EPA and others to keep ink from being a toxic material,” he points out.
Some paper, especially glossy paper, is a composite of paper and clay.
“The clay is not a problem in terms of the quality and purity, but it is something we have to be sensitive to when we process because it can change the way the conglomerate particles come out,” Charles says.
Sometimes, in the art field, glossy paper has varnish on it. Glossy ink also often has varnish in it, and some varnish is OK but other varnish can be bad, according to Charles. PittMoss just avoids glossy print material altogether.
For the most part, the glue in cardboard tubes and corrugated cardboard is an all-natural material, which is good, but that natural material may also contain micronutrients, such as boron, which will end up in finished PittMoss.
PittMoss uses a lot of post-industrial (rather than post-consumer) cardboard from remanufacturers, which Charles says is very clean. “Post-consumer is really a problem from the standpoint of the mixture of products you get in,” he adds.
PittMoss works with brokers that deal in recycled materials. He says the best quality of paper is primarily newsprint — the type of paper that newspapers are printed on. The offshoots and offcuts from newspaper printing have no ink on them, making them the cleanest and easiest to work with for PittMoss’ purposes.
Substrates made from cardboard rather than paper can be more rigid, but softer, because cardboard is a thicker fiber.
PittMoss is exploring using lignocellulosic fibers from agricultural production in the future. That includes wood fiber, sugar cane, industrial hemp, bamboo and Miscanthus grass. Charles notes that when they get into using agricultural products, they will have to test for and screen out materials that have been treated with pesticides.
Another concern with using organic substrates, in general, is human pathogens that can arise from composting that was not properly done. When PittMoss uses compost in products, the compost must meet USDA standards.
The U.S. Department of Agriculture’s Partnerships for Climate-Smart Commodities program is offering $1 billion for pilot projects to create market opportunities for commodities produced using climate-smart practices.
PittMoss is one such climate-smart commodity because it both replaces the use of peat and reuses recycled materials. Meanwhile, digging up peat from peat bogs releases carbon that had been sequestered over the course of hundreds of years.
As Dr. Merritt Turetsky pointed out in our conversation about peat moss and sustainability, peat moss may be effective in the horticultural industry but it is not the most climate-smart thing to continue using.
“It was the right thing for its time and place, and now it’s time to move forward,” Charles says of peat.
PittMiss isn’t heated or cooked at all, so the process of making it emits hardly any carbon. And it’s made from crops that took carbon out of the atmosphere as they grew. When PittMoss decomposes, some will remain in the soil for years and years as carbon-rich humus.
PittMoss for Different Applications
PittMoss Plentiful was designed for gardeners. It’s all-organic and intended for easy, all-natural growing. More research and development went into Plentiful than other PittMoss products, according to Charles, because it’s designed to support a thriving biome of beneficial bacteria and mycorrhizal fungi. That creates a good environment for roots to proliferate in.
That thriving biome needs airspace for rapid growth and respiration to take place, so Plentiful is engineered to have large particles for adequate airspace.
The pH in Plentiful is between 5.5 and 6.5. Charles says pH between 6 and 7 seems to be the most optimal for most beneficial microbes.
“You can’t depend on the microbes to do everything. You have to have the raw materials in there,” Charles says, explaining that poultry and cattle waste products give a good complement of minerals, carbohydrates and microbes.
“Making good potting soil with biology is like making fine wine,” he points out. “You have a period of fermentation and a period of aging.”
One set of microbes works well during composting and development, and second-stage microbes work on aging the compost. So when buying Plentiful, holding onto it for a while rather than using it right away can yield better results. It will age in the bag.
When using Plentiful in a container, it will be six to eight weeks before any nutrients need to be added. After that time, some of the minerals will be drawn down and in need of replacement. But Charles warns not to overdo it.
“Plants want to live,” he notes. “So if you keep it a little bit hungry, it’s going to develop its root system and everything to make it thrive.”
He says a plant will translocate its nutrients and its energy to where they will benefit the plant the most. “If it’s in low light, it’ll make large leaves and spread them out. If it’s got low nutrition, it’ll make more roots to go and forage more for more nutrients.”
For example, Charles experimented using poinsettias and found that when fed a low rate of nutrients, the plants had large and vast root balls.
PittMoss Performance is supplemented with minerals and slow-release coated fertilizer rather than organic materials.
PittMoss Prime is just the fibers. Charles says the “mad scientist” — the person who likes to get creative — enjoys using Prime and mixing it using the knowledge they have obtained.
Seed Starting with PittMoss Requires Some Knowledge And Restraint
Across the board, PittMoss products are designed for 4-inch pots and deeper, not shallow seed-starting trays. “Shallow containers get waterlogged because they don’t have the depth-of-gravity pull on these pipes in the soil,” Charles says.
A seedling blend needs air exchange between 8% and 20% in a shallow container, he says. Because existing PittMoss products can be overcompressed easily, they don’t work well in seed-starting applications.
A good gardener will know not to overpack PittMoss, but a true seed-starting product needs to be fine textured and needs to hold up to people who will abuse it, pack it and overwater it. “We are working on those things, but the fibers have to be more resilient against compaction,” Charles says.
Performance is a little high in nutrients for most seed germinating, but Plentiful has a very good nutrient balance for germination, he says.
Hydraulic Conductivity and Tortuosity
Tortuosity is the difficulty that water has in getting from one side of the substrate to the root.
“You want the water to be able to get to the root and get to the microbes around the root, and when it’s growing rapidly and aggressively in the heat, that area right adjacent to the root is going to dry first,” Charles explains. “And then the far edges are going to have water, but it has to get to the root. So the rate at which it gets there is important.”
When a growing medium has good hydraulic conductivity, a gardener does not need to water multiple times a day in the heat. Just once a day will be adequate. If there is good hydraulic conductivity, when the area around the root dries out, water will move there from other areas in the container.
Water PittMoss Less
“People who love their plants will water ’em to death and love ’em to death,” Charles says.
He typically sees this in the early season or mid-season, when it’s not as hot and drying out doesn’t happen rapidly.
Because PittMoss holds water so well, it’s recommended to water half as much or even two-thirds less than you would water conventional potting mix. He also notes that PittMoss tends to dry on the surface and act as mulch while there is still a great supply of water beneath.
Other PittMoss Blends
PittMoss offers two peat-reduced blends and a peat-less blend containing coir.
PM1 contains 30% PittMoss plus Sphagnum peat moss, perlite and a wetting agent. Perlite, or “white specs,” as Charles calls them, “are there for aesthetics. They don’t do much,” he says. Growers, in a survey, preferred a mix with white specs, 90 to 10, over one without, he adds.
It’s great in hanging pots because it will keep the pots moist when the owners go away for the weekend and aren’t around to water.
PM2 is similar to PM1 but it contains 25% pine bark. It is heavier and is better for nursery cans and containers that you don’t plant blowing over in the wind.
COCO Complete is a peat-free coir and PittMoss blend using coir from Mexico. Mexican coir is not loaded with sodium like coir from the Far East often is, and it also travels less to get to PittMoss’s manufacturing facility.
Because coir is naturally high in potassium, PittMoss can use coir in up to 30% of the mix before the potassium level gets too high. Before adding any more coir, it must be flushed of potassium, but that requires a lot of fresh water.
PittMoss is basically sold out of COCO Complete through June due to supply-chain issues, Charles says. “It’s one of the best performers compared to some of the peat-based mixes,” he says.
“We have to keep in mind that we’re having a lot of fun doing these things and everything we do in the garden has an impact, especially on our neighbors’ water and on our neighbors’ land. … you cannot damage the soil or damage the land and then leave,” Charles says. “I mean, that’s irresponsible …”
I hope you enjoyed my conversation with Dr. Charles Bethke. If you haven’t listened yet, you can do so now by clicking the Play button on the green bar near the top of this post.
Have you tried PittMoss as a peat alternative? Let us know your results and experience in the comments below.
Links & Resources
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joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
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