One hopes that this could never happen but you could, as a survivalist, find yourself completed devoid of any food in the winter. Here are some suggestions of what you could forage in the wild so that you do not starve.
One food that survives the cold and the snow is the oyster mushroom. They are best in the summer but you can find the fruits growing on a log or a tree stump. Sometimes, if the weather warms, you can actually find fresher mushrooms that are fruiting. Make sure you have a guide on hand so that you do not accidentally pick a mushroom that is poisonous. You can eat these cooked anyway and also use them to make a stock for soup. If there is a dehydrator in your shelter you can also dry them and eat them as a snack.
Another type of edible mushroom is known as Blewits. It is also sometimes called the Blue or Bluebutton mushroom. Field Blewits (Lepista saeve) are often found in parks, gardens and on grassland and they are still abundant from October through until January. They are toffee colored mushrooms that have a floral smell. You can find them beneath snow and frost and they keep well. They cook well as a soup in powder milk.
Nettles are also easy to identify. They are nutritious even if they are all gray and dried up. Sometimes, in the winter, you can find new nettle leaves growing at the base of the plant. When picking these be sure to wear gloves as many of them still have prickles. You can use nettles as a soup stock or make a very nutritious tea out of them.
Chickweed is another option. This is a small plant with a white flower that is usually found at the edge of fields and vegetable patches. They like to grow where there I disturbed grounds. Chickweed is very tasty and tastes like a cross between spinach and watercress.
Yet another standby that is still good in the winter is the humble dandelion. You will not find the flowers blooming throughout the winter months but you will find the leaves in the Spring. During the winter you can pull up the roots and then grind them up to make a primitive yet nutritious coffee. Dandelion roots are very good roasted. You can also fry them in oil and soy sauce to make a delicious dish.