key growing information

Oyster Mushrooms from Sawdust Spawn | Key Growing Information

How to grow oyster mushrooms from sawdust spawn on logs, stumps, pillars, beds or in containers: spawn care, timing, substrates and tree species, inoculation, moisture, fruiting, harvest, pests and safe eating.
By Hensley’s Seed Co.

Oyster Mushrooms from Sawdust Spawn | Key Growing Information

Oyster mushroom sawdust spawn.

CULTURE:

Sawdust spawn lets you grow oyster mushrooms on logs, stumps, pillars (also called totems), in beds or in containers. Logs, pillars and containers are all common for commercial growing, while stumps and beds make good use of spare corners. Pillars and beds suit beginners since they need no special tools. Mushrooms need plenty of moisture, so pick a spot that's easy to reach and check, shaded at least part of the day all year, and ideally close to water. Different climates may call for adjusted methods, and some options are covered below.

SPAWN STORAGE:

Take the spawn bags out of the shipping box as soon as they arrive, and untuck them so the filter patch is exposed and air can move. If mushrooms have already started forming on the filter patch, remove them gently without tearing the filter or bag. Mushrooms grow from mycelium, a mass of whitish threads; in a spawn bag it can look like fuzzy mold, but that's healthy growth. Fresh spawn works best, but if you must wait, refrigerate it for up to 6 months. Keep the bag sealed until the day you inoculate, since opening it early greatly increases the risk of contamination.

DAYS TO MATURITY:

Oysters colonize fast: logs, stumps and pillars may fruit in 6–12 months, containers in as little as 10 days to 3 weeks, and beds started in spring in 2–4 months. Timing always depends on conditions, substrate, species and the spawn-to-substrate ratio, and fruiting begins only after the mycelium has fully colonized the substrate. Small logs colonize faster than big ones, and stumps can take longer.

SUBSTRATE SELECTION:

Oysters are especially vigorous and grow on many substrates in containers or beds. Straw is the favorite, but sawdust, wood chips, farm waste and more also work. Our chart, Substrate Types for Growing Mushrooms , has more detail. Fresh substrate is less likely to carry pests and competing fungi than material that has aged.

TREE SELECTION FOR LOGS, STUMPS, OR PILLARS:

Certain trees suit certain mushrooms better. Oysters do best on aspen, cottonwood, tulip tree and willow, but grow on a wide range of trees. Our chart, Suitability of Tree Species for Growing Mushrooms on Logs for details. Healthy trees with sound bark can be cut any time of year except in spring, from bud swell until the leaves are fully out, when the tree is putting its energy into new growth. The best time is the month before buds swell.

LOG INOCULATION:

For logs, cut trees at least 3" across into the lengths you want. Inoculate within a week or two of cutting, unless you can keep the logs frozen and moist, for example under snow in a northern winter. With a 12 mm bit, drill holes 1" deep every 4–6" along rows 2–3" apart, offsetting the rows in a diamond pattern down the log. Break up the sawdust spawn, then load an inoculation tool by jabbing its tip into the spawn a few times, line it up with a hole and press the plunger to push spawn in, leaving it level with or just below the bark. Repeat for every hole. Brush or dab melted wax over each filled hole to keep the log from drying out and to keep contaminants out. In dry climates, wax the cut ends too.

PILLAR INOCULATION:

For pillars, cut a larger-diameter tree into at least two 6–18" sections plus one 2" slice to use as a cap. As with logs, inoculate within a week or two of cutting unless the wood can stay frozen and moist, such as under snow in a northern winter. Set a piece of cardboard on the ground and spread a 1" layer of spawn in a circle about as wide as the logs. Stand a 6–18" section on it, add another 1" of spawn on top, then stand the next section on that. Finish with a last 1" of spawn and the 2" cap. You can stack as many sections as will stay stable.

STUMP GROWING:

Freshly cut stumps of a suitable tree can also be inoculated with sawdust spawn, and they can keep producing far longer than logs. Follow the log method, with two extra steps: first girdle the stump by stripping a ring of outer bark around its base so it doesn't sprout suckers, and when inoculating, drill holes in the cut top of the stump as well.

CONTAINER INOCULATION:

Containers work indoors or out. Oysters fruit from either the sides or the top. For side fruiting, use a container with side openings, such as a milk or bulb crate, or drill holes; for top fruiting, the open top is enough. Half-inch holes let mushrooms fruit while limiting moisture loss during colonization. Clean the container first to lower contamination risk; you can also pasteurize the substrate with hot water or with cold water and hydrated lime. Start with moist substrate, ideally about 50% moisture, meaning it weighs about twice its dry weight. Break up the spawn and mix in ½ to 1 full bag per 5 gallons of substrate; more spawn colonizes faster and more reliably and is the better choice for beginners. Fill the container, either mixing thoroughly or alternating layers of substrate and spawn.

MUSHROOM BED INOCULATION:

Oysters also grow in outdoor beds, between garden rows, or anywhere you have enough suitable substrate. Coverage depends on bed depth and spawn ratio, but one bag of spawn generally does a bed about 4' x 4'. Clear the site of unwanted plants and debris. You can soak the substrate first, water between layers, or water everything well at the end. Start with 1" of substrate, crumble spawn over it, breaking up big chunks, then keep alternating 3–6" layers of substrate with spawn until the spawn runs out or the bed is deep enough. Finish with a layer of substrate to protect the spawn.

COLONIZATION:

Keeping moisture up matters most between inoculation and fruiting, while the mycelium grows but no mushrooms show yet. Let this stage happen out of direct sun. For pillars or containers, a tarp, straw mulch or similar cover helps hold moisture; take it off when pins (baby mushrooms) start forming on the surface. Keep logs near the ground but not touching it, and stack them closely so too much airflow doesn't dry them out.

CONSIDERATIONS FOR FRUITING ON LOGS:

Once logs are fully colonized, which sometimes shows as mycelium on the cut ends, rearrange them for better airflow and easier picking. The first fruiting happens on its own. After that, for more regular harvests, you can "force fruit" logs by soaking them in cold water for no more than 24 hours, which you can try with oysters, though it works best with Shiitake. Leave about 8 weeks between flushes when forcing.

HARVEST:

Clusters grow fast near maturity, so check at least once a day. Twist or cut each cluster off at the base of the stems, picking just before the caps flatten, while the edges still curl under. Overripe mushrooms bruise easily and don't keep as long. Fading, discoloration or loss of firmness are signs they may be past their best, as flavor and texture decline with age.

PRODUCTION WINDOW:

How many flushes you get depends on the substrate's type and density, the conditions and the species. On logs, bigger diameters mean a longer production window, and stumps and pillars, being wider still, can produce much longer than logs. In the North, a handy rule is one year of production per inch of log diameter; in mild areas with a longer growing season, expect less. Containers and substrates vary too much to predict yield reliably. Beds can keep producing for a few years if you add enough fresh substrate each year.

PESTS AND DISEASE:

Mold can grow on sawdust spawn damaged in shipping or on mushrooms stored too long; never eat moldy mushrooms. Spreading diatomaceous earth on beds or around the base of logs helps against slugs. Animals are usually a minor problem and rarely take the whole crop, and row cover such as Agribon-15 helps keep them off. Picking young also tends to mean less pest damage.

CAUTION:

Always cook mushrooms thoroughly. When trying a species for the first time, eat only a little to check for allergies. Logs or substrate kept outdoors are more likely to be colonized by other fungi, so be sure of a mushroom's identity before eating it, as it could be a local wild species.

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