You’ll need strong legs and ankles, knowledge of how to navigate and stay safe on the trails, a completely new running wardrobe, and a whole new attitude to race food.
Add some extra distance to your marathon training schedule. You can adjust a marathon plan to a 50K training plan by adding 10 to 15% extra weekly mileage or training time.
It's a significant challenge. A trail ultra can include steep hills, mastering uneven terrain and there can be long sections between aid stations. Some races even start in the middle of the night!
Get some specific trail running shoes and train on the trails. Find some other more experienced runners to train with and get used to navigating and running on uneven surfaces.