Honestly, after thinking about it, I may just use Roundup. Here's the situation: I should have sprayed last year, but I never expected such quick regrowth. I only had the timber heavily thinned two years ago in winter (Jan-Feb). Normally you have weeds and "food stuffs" in a timber cut area for three summers. But with a winter cut, and most of the sites being wetter north-facing slopes that had a lot of white oak (best growth conditions), now the third summer is already a complete canopy of hardwood saplings. No food stuffs or grasses in the area because the hardwood regrowth has already canopied out 5-6 feet high. The only plant that could keep up with the growth was blackberry, so there's a lot of blackberry mixed in. The canopy is already so complete that no spray is going to hit the ground. Most of this heavily thinned timber area (100 total acres broken into 7 patches) is just going to be allowed to go through the normal regrowth process, which is usually 3 years of summer food stuffs (weeds and newly sprouted saplings), followed by 3 years of complete canopy hardwood saplings (great cover) followed by another 10 years of moderate cover as all those hardwoods grow into pole timber stage. But I would like to create some small patches mixed in with all this regrowth that stays in the very early stage of growth (that first 3 years of food production).
I have been looking at "selective" herbicides because I didn't want to kill off any grasses that have filled in. But the regrowth has been so fast saplings have already choked out all the grasses and broadleaf weeds. I'm thinking of just going non-selective with Roundup simply to kill out some 1/2 to 1 acre patches in these big areas of regrowth. Plus, Roundup is a heck of a lot cheaper than the expensive selective herbicides.