Long story short: yes, you have to soak Cedar planks before cooking with them.
The good news is soaking a plank for 15 minutes is the optimal soaking time, so by the time your grill is preheated and food is prepared, you’ll be ready to start cooking!
What if I don’t soak my planks?
If you don’t soak your planks you run the risk of your plank lighting on fire, as you’re basically putting a dry piece of wood on a hot grill. Grilling with a dry plank won’t give as much smoky flavor to the food you’re cooking, since much of the flavor comes from the water evaporating out of the plank as it’s exposed to the heat of your grill. With a soaked plank, the food on the plank will pick up the flavors as they leave the plank, which is why we recommend keeping your grill closed as much as possible.
We did our research
Our Executive Chef Matt did a deep dive into the subject and ranked the flavor achieved from planks that weren’t soaked at all to those that were soaked for an hour. As you can see in his results below, 15 minutes of soaking resulted in the most flavor, with the least amount of time spent.
If you want to have soaked planks ready to go at all times, a great trick is to soak a couple of planks and freeze them in a freezer bag. Make sure to put parchment paper between the planks to keep them from freezing together. When you want to use a plank, just take it out of the freezer and it’s ready to use.