ECOLOGICAL THREAT : dry to mesic prairies and stream banks are vulnerable to be Siberian elm invasion. Thickets of seedlings soon form around seed-producing trees bare ground areas animal and insect mounds and other disturbed areas. Wind carries seed to distant areas where new colonies can form. This tough exotic survives under conditions not easily tolerated by other species allowing it to take advantage of open ground and resources otherwise used by native plants. Fast growing seedlings of Siberian elm quickly overtake native vegetation especially shade-intolerant species compounding the problem.