You know I have the same issue. I am doing an entire renovation for a front yard that's about 25 years old. I sprayed 6 gallons (2 backpacks) on this area. I mixed at 4oz/gal 9label says for hard to control use that rate). I sprayed ivy, azaleas, liriope and some scattered broadleafs 2 weeks ago tomorrow. The whole yard is heavily shaded, only get slight filtered sunlight. I stopped by last Sat and hardly anything. I called the homeowner last night and they said no visible difference! Damn it! I used a PBI Gordon product called Glyphomate. It's 41% glyphosate with a surfanctabnt already mixed in safe for aquatic use (spraying in a yard that drains into a creek) It has to be the shade don't you think? I was thinking of those packets because the % of gly is higher. However, maybe that doesn't matter since it's shaded. Im going back to spray again tomorrow. Maybe I will mix at 6oz/gal?