Interference to Hardwood Regeneration in Northeastern North America: Assessing and Countering Ferns in Northern Hardwood Forests

The extremely dense shade cast by spreading ferns, particularly hayscented, New York, and bracken ferns, interferes with the survival and development of tree seedlings in northern hardwood forests. Excessive bracken frond litter and hayscented fern root mats can also prevent adequate germination and seedling development. In addition, the herbaceous cover may harbor detrimental small herbivores, while large ones often preferentially browse seedlings that grow through this layer. Increased understory light levels after an overstory disturbance, abundant soil moisture, fire, and herbivory promote ferns, whereas excessive and repeated cold or drought deter fern development and propagation. The most promising control methods repress ferns until seedlings cast adequate shade to inhibit further development of the fern layer. When ferns cover more than 30% of the understory, well-timed applications of either glyphosate or sulfometuron methyl have successfully controlled hayscented, New York, and bracken ferns. Two carefully timed mowings annually for at least 2 years have also provided long-lasting control on level, accessible sites. Deer populations must be reduced where browsing prevents development of desirable plants.