Roundup Weed and Grass Killer Super Concentrate is the best Roundup brand concentrate value for really widespread weed problems. For use around flowers, shrubs and trees; on patios, walkways, driveways, gravel areas, and mulch beds; along fences, edging and foundations; as well as large areas such as lawn replacements or garden plot preparation. Rainproof in 30 minutes. Weeds usually yellow and wilt in 2-4 days. Active ingredients: 50.2% Glyphosate.