Effects of the non-indigenous shrub Rhamnus frangula L. (glossy buckthorn) on tree recruitment, herb cover, forest floor plant species richness, and R. frangula recruitment were tested in two southeastern New Hampshire Pinus forests using a randomized complete-block field experiment. The treatment, applied in January of 2000, was the presence of well-established R. frangula populations with three levels: R. frangula absent prior to experiment (“uninvaded”), > 90% R. frangula cover (“Rhamnus present”), and removal of > 90% R. frangula cover (“Rhamnus removed”). After 2 years of measurements, Rhamnus present had significantly lower first-year native tree seedling density than Rhamnus removed and uninvaded plots (0.11, 0.40, and 0.40 seedlings/m2 respectively). First-year native tree seedling density in the Rhamnus removed and uninvaded treatments were similar. Neither percent herb cover nor plant species richness were significantly affected by the removal of R. frangula in the two years following treatment. We believe these results indicate that the presence of dense R. frangula inhibits the establishment of tree seedlings. Rhamnus removed plots sampled one year after removal had five-fold greater first-year R. frangula seedling density than the other treatments. However, after two years first-year R. frangula seedling density was similarly low in all treatments (< 0.5 R. frangula seedlings/m2). Control efforts for R. frangula may need to focus on conspecific seedling emergence for at least two years following initial control.