Sandi, I learned long ago to get my potted plants off the ground. I literally grow hundreds of tropical plants under large oaks and cedar trees. I build platforms out of 2x2" and 2x4" treated pine. The platforms are anywhere from 18"W x 24"L to 24"W x 36"L. I simply cut 2-3 pieces of 2x2 (depends on how long the platform is) the width of the platform. Those 2x2's will become the "feet" that rest on the ground. The 2x4's are the platform. Thus, the platform will hold plants approximately 3.5" above the ground. That stops all tree-root invasion.
