More often than not, people use grain spawn to inoculate straw. Why not sawdust spawn? No reason in particular, but let's explore it a little bit below.
For anyone who is not familiar with the process, let's briefly explain. Chopped straw is pasteurized (cooked) in hot water to reduce the amount of contaminates it may contain (ie. molds, bacteria). After the straw drains and cools it is inoculated (planted) using oyster mushroom spawn (seed). After only a few short weeks beautiful oyster mushroom emerge, and can continue doing so for 2-3 months.
Here at F&FP our most popular type of spawn is called grain spawn. We use it when we can, but there are times when grain spawn becomes scarce here for our own use due to customer demand. When grain is in short supply we turn to the next best thing...sawdust spawn!
Which is better?
As with most things, there are pros and cons to each.
Grain spawn is easier to break up, and is easier to pour. A gentle massage of the bag will get the job done. Sawdust spawn on the other hand, requires a firmer hand. If you have some pent up frustration we suggest you choose sawdust spawn. The oyster mycelium does a fine job of turning tiny sawdust particles into one solid brick that is easiest to break up with a firm fist. Do, however, be careful not to break the spawn bag.
Sawdust spawn has the advantage when it comes to spawn run time (time until full colonization). While grain particles are larger and cover a larger surface area individually, there are not as many inoculation points as there are when sawdust is sprinkled throughout the straw. On average we have mushroom pin formation two days earlier when using sawdust spawn.
Whether using grain or sawdust we have gone to using a 5-10% inoculation rate. We recommend 10% when just starting out. That is, 5% of the weight weight of the straw is the weight used in spawn. Bags of grain come in 4 lb. units and can plant about 4 sleeves (polyethylene 4 mil bags). Large bags of sawdust spawn come is 5 lb. bags and can plant 5 1/2 sleeves.
Now for the big question, which type of spawn produces more mushrooms? We have seen some impressive numbers (in terms of yield) when using both grain spawn and sawdust spawn. On the opposite end of the spectrum, we have also seen low yields from both types. Most of the time my diminished yields are due to other factors including (but not limited to) dirty straw, humidifier issues, or fungus gnats. So truly in this case, it's a matter of personal preference.