We have field, once a horse pasture, now being overgrown with many (~100) black walnut saplings, some 10 feet tall. we want to remove the them. Our plan is to chain saw at the base and paint the cut stump with glyphosate. When to do? Spring? What concentrate glyphosate? More than one application? What to do with cut saplings? Burn or Recycling Center? Thanks in advance for any advice.