The Ardennes forest is mostly made up of connifers (pine trees). The trees will remain green all year and the ground in the forests is covered with a light red/brown blanket of fallen 'needles'. Ferns and Blueberry bushes are also very common in the forrests.
If you look at a map of Belgium, the area between the towns of Malmedy, Spa, Verviers, Eupen and the German border at the East, is marshland . A lot of tall grasses cover the very spongy ground; connifer forests are also common in that area. In fact, it's not recommended to go outside the main roads without a 'local' and lives are lost every year with tourists disappearing in the marsh...