By leaving the fronds from last year's ferns, you are increasing the organic portion of the soil. Ferns love moist, shady areas with highly organic soil, so anything you can do to increase the organic matter will encourage them, as well as holding moisture. Leave the old fronds this fall; they will help insulate the plants as they catch snow. In addition to leaving the old foliage to improve the soil, go a step further and add 2 to 3 inches of bark or wood chips to protect the crowns (next year's growth) which are exposed above the ground level. In the spring, carefully prune off the old fronds, avoiding the tight clusters of "fiddlehead," the new growth not yet emerged. Also in the spring, apply a bit of balanced fertilizer, (10-10-10) to ensure the plants have adequate nutrition.

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