Grow Food, Not Lawns Growing Shiitake Mushrooms is Easier Than You Think Did you know that shiitakes are easy to grow in the home garden? Well they are and they only require a few items beyond the spawn (seeds). But before you jump into the fungus business, there are a few things you will need to know. 1. Shiitakes will produce 6 to 18 months after inoculation and will continue to produce for four to six years.