Horrified at that summer forecast? Wondering what happens to mushroom logs or beds outdoors if the temperatures seem like they are approaching bread-baking territory? Most of all, is there anything you can do about it?
How Much Heat Can Mushrooms Handle?
Mushroom mycelium, especially that of many of the mushrooms we cultivate, can tolerate higher temperatures, but by no means thrive in it. Mycelium loves warm temps but not hot; and steadily increases in productive growth until a peak temperature of 77°F is reached. After temperatures edge above that, though, it begins a rapid decrease in productivity until temps reach 104°F, where thermal death becomes possible.
But before you panic at a forecast that threatens to go over 100°F, consider these points:
1. Most likely, your mushroom logs or beds live in the forest. Remember that temperatures in the forest are usually cooler than daytime temperatures measured at any given time.
2. Mycelium growth is beneath the bark and benefits from that protection from hot and cold temperatures. And unless the bark is very thin, mycelium should get a few degrees of heat relief. If you do have thin-barked logs such as small-diameter shiitake logs, make sure they are low to or directly on the ground to protect them from sun. Just remember, if they're directly on the ground, you will want to elevate them back up after the hottest of days pass!
Tips for keeping mushroom logs and beds cool
1. Logs and beds are stacked near the ground or low to the ground, where evaporative cooling from plants and soil can aid in keeping temperatures down. If you have high stacks of logs, bring them down to ground level.
2. Provide additional shade from old window screens, shade cloth, white fruiting blankets, row covers or pine boughs. This can help keep temperatures in a safe range.
3. Create extra evaporative cooling. While just being in a wooded environment naturally provides some moisture movement, a light misting hose or wet blankets over the stacks or piles can help. Heavy watering can be a little risky as it may stimulate unwanted fruiting, but sprinkling with an oscillating or impact sprinkler for a short period (less than 1 hr) can wet log/ bed surfaces and create some evaporative cooling without risking fruiting. Do this daily, especially if your logs are exposed to sunny intervals, until the hottest temps have passed.
Mushroom mycelium is resilient and very possibly will give you a great fruiting response once cooling rains or soaking logs for the time you DO want fruiting to occur.