What is spawn to bulk?

The spawn rate, the amount of spawn as a percentage of the bulk substrate, trades cost against speed. Cornell's Small Farms Program says more spawn makes the mycelium grow through faster, but the substrate "likely will not produce a larger amount of mushrooms", so you spend more on spawn per pound. For a new grower, it adds, a high rate "can really boost the success rate" (Cornell).

A Penn State trial on an oyster species shows the speed gain. Spawning at 3.75% of wet substrate weight brought production a mean 9.2 days sooner than 1.25%. Yield peaked at 3.75–5%, so a very low rate can cost some yield too (Penn State, via PubMed).

Use more spawn on pasteurized or other non-sterile substrates than on sterilized ones.

Bulk substrate	Spawn rate	Source
Pasteurized straw, oysters	5–10% by weight or volume	UF/IFAS
Non-sterile substrates in general	5–20%	GroCycle
Fully sterile substrates in general	1–3%	GroCycle
Pasteurized cottonseed hulls and straw, oyster	Top yield at 3.75–5%	Penn State
Supplemented sawdust, shiitake	One 5-lb bag per 200 lb (2.5%)	Cornell

The shiitake row comes from a Fungi Ally trial reported by Cornell: one 5-lb bag of spawn colonized anywhere from 100 to 200 lb of substrate in about 8 weeks, but at 250 lb, colonization slowed and contamination rose. The percentage is our arithmetic. Our pink oyster grain spawn guide works out about 4–5% for sterilized sawdust from vendor figures.

A ratio says the same thing: 1 lb of spawn to 10 lb of substrate is 1:10, or 10%. Weigh both, or measure both by volume; the two don't give the same number.

1. Break up the spawn before you open it. GroCycle shakes jars "to break the grains apart, then mix them into your bulk substrate" (GroCycle).
2. Work as clean as the substrate needs. Straw and logs are fine to inoculate in open air with a clean table and hands. Supplemented sawdust, such as Master's Mix, needs a lab-like setting (Cornell).
3. Spawn straw as soon as it drains and cools, mixing it in bulk or in layers (UF/IFAS).
4. Mix the spawn through. In the Fungi Ally bags, spawn shaken through 5-lb bags colonized them in 14 days; spawn left on top took 24 (Cornell).
5. Incubate. UF/IFAS runs oyster straw bags at 75–77°F (24–25°C) for two to three weeks, until the whole bag is white (UF/IFAS).

Our grow timeline lists colonization times by species.

• A warm incubation room. Cornell says incubation shouldn't go above 80°F (27°C) and is ideally around 70°F (21°C). The core of a 5- or 10-lb sawdust bag can run 10–15°F warmer than the room, so 80°F outside can mean 95°F inside (Cornell).
• Cutting spawn too fine on a first grow. Cornell suggests starting high, then lowering the rate as you dial in the process and watching whether colonization slows (Cornell).

In Hypha, each bulk block gets a reminder to move into fruiting, then flush reminders.