Frequently Asked Questions

Spawn is the seed of a mushroom crop. It's live mushroom mycelium grown onto a carrier, like millet grain, that gets mixed into compost to start a grow. Good spawn means a strong crop. Bad spawn means problems from day one.

See also: What is a spawn carrier? What is biological efficiency?

Amycel makes the spawn most of the world's commercial mushroom farms start with. We develop the genetics, grow the spawn, and back it up with hands-on support from people who've grown mushrooms themselves. Spawn Mate, our supplement line, is the North American standard for Agaricus production.

See also: What strains does Amycel offer? Are Spawn Mate supplements available in Europe?

Amycel has been producing commercial mushroom spawn since 1979. We started as the spawn operation for Monterey Mushrooms and have been at it ever since. Our production facilities are in California, Texas, and Vendôme, France. Our North American offices are in Pennsylvania and California.

We ship to 37 countries across 5 continents. North America, including the US, Canada, and Mexico, is handled from our Pennsylvania and California offices. Europe, the Middle East, and Africa are handled by our team in Vendôme, France.

Yes. Some Amycel and Spawn Mate products are OMRI listed for organic production. Ask your rep for the full list.

Yes. We have a full production facility and sales team in Vendôme, France. Our EU lineup covers white strains, brown strains, specialty strains, and spawn carriers. Note: Spawn Mate supplements are US only.

Use the contact form on this site or reach out to your regional rep directly. North American growers go through our Pennsylvania or California offices. European growers go through Vendôme. Our reps are former growers. They pick up the phone.

Heirloom and Brawn are both patented brown hybrid strains of Agaricus bisporus, sold only by Amycel. Heirloom is heavy-bodied and built for Portabella, Baby Bella, and Crimini production. Brawn caps tend to run darker and work well across a range of size mixes. You cannot cross-CAC either strain with anything else on the market.

See also: What brown strains does Amycel offer? Are Amycel strains patented?

Exxcalibur is Amycel's newest white hybrid, released in 2023. It combines the body of Phoenixx with the speed of Triple X. Stems are thicker, clumping is reduced, staggering between flushes is better, and pick rates run 20% to 25% faster. It was built for operations feeling the squeeze on labor.

See also: What white strains does Amycel offer? What is biological efficiency?

We offer four white and off-white hybrids. Phoenixx is large, heavy, and productive. Triple X is our fastest colonizer, high density, and works in a wide range of conditions. Delta is a moderate pinner with smooth, round caps that hold well without opening. Exxcalibur is our newest, with pick rates 20% to 25% faster.

We have three. Heirloom is a heavy-bodied brown hybrid built for Portabella, Baby Bella, and Crimini production. Brawn runs darker and suits varied size mixes. Kodiak launches Summer 2026. Taller mushrooms, denser stems, fewer opens, up to 50% less water for the same yield, and built for robotic harvesting.

See also: What is the difference between Heirloom and Brawn?

Kodiak is Amycel's newest brown hybrid, launching Summer 2026. It grows taller mushrooms with dense stems that don't discolor at the cut. Opens drop from around 7% to 3%. It needs up to 50% less water for the same yield. Shelf life is longer. And it was designed with robotic harvesting in mind.

Yes. Amycel's EU product line includes commercial spawn for shiitake, pioppino, yellow oyster, and Karabella, a sporeless oyster developed with Wageningen University. Specialty strain availability in North America varies. Contact your regional Amycel rep for current offerings in your market.

Heirloom is what most portabella growers use. It's heavy-bodied with consistent color, density, and shelf life. Brawn is a good option if you want a darker cap. Both are patented and only come from Amycel.

Heirloom is the go-to for crimini. Medium to dark brown, minimal scaling, and good refrigeration life. Brawn is a solid alternative for a darker result. Both are patented and exclusive to Amycel.

Both are major commercial mushroom spawn companies. Amycel's difference is in the genetics, the substrates, and the support. Our R&D program runs 32 dedicated test rooms, one of the largest mushroom testing programs in the world. Our North American sales team are former growers, not just salespeople. They visit farms and troubleshoot in person.

See also: Are Amycel strains patented? What spawn carriers does Amycel offer?

Yes. Heirloom, Brawn, and select other strains are patented and only available from Amycel. Exxcalibur and Kodiak are proprietary hybrids developed in-house.

Agaricus bisporus is the most widely grown mushroom in the world. It covers white button mushrooms, cremini, portabella, and Baby Bella. All Amycel white and brown hybrid strains are Agaricus bisporus varieties built for commercial production.

A spawn carrier is what the mushroom mycelium grows on before you mix it into compost. The carrier affects how fast the spawn runs, how well it resists green mold, and how evenly it spreads. Common options are millet grain and synthetic substrates.

See also: What is the difference between Millet, Exxpress, and Onyxx?

We offer three substrates plus PAC casing spawn. Millet is our traditional grain carrier. Exxpress is fully synthetic and grain-free. Onyxx is a hybrid of both. PAC is our premium casing spawn and works with all Amycel strains.

Millet is the classic. Small grain size, good even coverage, tried and true. Exxpress is fully synthetic. It runs faster than millet and its formula helps fight green mold. Good for operations cutting back on grain. Onyxx is a hybrid. You get the speed of synthetic with the energy of grain. Your rep can help you pick the right one.

See also: What is Trichoderma green mold? What is PAC casing spawn?

PAC is Amycel's premium casing spawn. You apply it to colonized compost to get even, consistent pinning. It combines high-quality compost and nutrients to work well even when soil moisture varies. Available for all Amycel strains.

Grain spawn uses cereal grains like millet as the carrier. It's the traditional standard in commercial Agaricus growing. Synthetic spawn uses a non-grain mix. It typically runs faster and fights green mold better. Amycel's Exxpress is fully synthetic. Onyxx blends both.

Trichoderma is a competitor mold that gets into mushroom compost and competes with your mycelium for nutrients. It cuts yields and spreads fast. Amycel's Exxpress and Onyxx carriers include formulations that help keep it in check. Spawn Mate's Titanium supplement does too.

A supplement is a nutrient additive you mix into compost to boost yield across multiple flushes. Compost only has so much nutrition. Once it runs out, later flushes get weak. A good supplement keeps your third and fourth flushes worth picking.

See also: What is delayed-release technology? What is biological efficiency?

Delayed-release means the supplement releases nutrients slowly as the crop grows, not all at once. If nutrients flood the compost too fast, it overheats. That kills mycelium and invites green mold. Slow release prevents that. Every Spawn Mate supplement uses it.

See also: What is thermogenesis? What supplements does Amycel offer?

Thermogenesis is what happens when compost nutrients break down too fast and generate heat. Too much heat kills mushroom mycelium and opens the door for competitor molds. Delayed-release supplements control how fast nutrients break down to keep temperatures in range.

Spawn Mate supplements are for commercial Agaricus production in the US. The lineup includes Promycel Gold at 54% protein, the industry benchmark. Titanium at 48% protein with green mold protection. Ultimate at 48% protein, plant-based, runs cooler. SMO PRO 2.0 and SMO PRO 58 for certified organic operations. PG Natural 2.0, also organic compliant. Plus TBS, SM 25, and Spawn Mate II SE, built for specialty crops like oyster mushrooms.

See also: Are Spawn Mate supplements available in Europe? What is delayed-release technology?

No. Spawn Mate is US only. European growers should contact their Amycel EU rep. The EU lineup includes Promycel Gold and Titanium.

High-performance delayed-release supplements can increase yield by 10% to 20% or more, measured as biological efficiency. Results depend on your compost, strain, conditions, and how you apply the supplement. Your Amycel rep can help you build the right program.

At spawning, mixed into the compost at the same time as the spawn. Or at casing, added during the casing layer stage for a late boost to later flushes. Many commercial operations use both.

Protein concentration tells you how much nitrogen and energy the supplement gives your mycelium. Higher protein means more fuel for dense, heavy caps. Spawn Mate supplements range from 27% protein in Spawn Mate II SE for specialty crops, up to 58% in SMO PRO 58 for high-yield organic production.

Biological efficiency, or BE, measures how much fresh mushroom you get compared to the dry weight of the substrate used. It's the standard way to measure crop performance. A good supplement program is the fastest way to improve it.

Slow or incomplete spawn runs usually come down to three things: compost quality, spawn rate, or the carrier substrate.

Poor compost preparation, low nitrogen levels, or inconsistent moisture can all slow colonization. The wrong spawn carrier for your conditions can too.

Exxpress and Onyxx both run faster than millet and can help in operations where spawn run speed is a persistent issue.

If you are seeing slow runs consistently, compost analysis is the fastest way to find the cause. Amycel provides complimentary compost analysis for its customers using near-infrared technology.

See also: What is the difference between Millet, Exxpress, and Onyxx? What is Amycel's grower support?

Inconsistent pinning is usually a casing issue.

Uneven moisture distribution, poor casing quality, or inconsistent application of casing spawn are the most common causes.

PAC, Amycel's premium casing spawn, is specifically formulated to promote even pinning across variable soil moisture conditions. CO2 levels and temperature breaks at the right time also play a role.

If pinning is uneven across your beds, your Amycel rep can walk the grow room and help identify the cause.

See also: What is PAC casing spawn? What is Amycel's grower support?

Cap quality in commercial Agaricus production is affected by strain selection, humidity management, harvest timing, and supplement program.

Strains like Delta produce smooth round caps that hold without opening, making them ideal for fresh market quality standards. Exxcalibur produces thicker stems and cleaner caps with better staggering between flushes.

On the supplement side, Spawn Mate supplements include lipids and micronutrients that improve cap whiteness and shelf life alongside their yield benefits.

If cap quality is inconsistent across flushes, the issue is often nutrition in later flushes rather than strain performance.

See also: What white mushroom strains does Amycel offer? What mushroom supplements does Amycel offer?