A nice addition to the Alchemical Powders (and to the Inventory of Gardening Vendors) would be Powder of Startling Toxicity.
Simply put, this amped up version of Tree Poison that will destroy every Tree IN YOUR OWN YARD.
It won't work in public streets, or in other people's back yards. Only the owner of the house is able to deploy this highly toxic concoction.
Why would anyone even want this? Well, if you have ever moved into a previously occupied house and the trees growing there are not the trees you want to grow, you are faced with going through the process of killing each and every single tree individually, administering the poison, having to sit by as the helpless tree screams out for antidote. Once you have killed the first tree you get to move on to the next tree and do it all again. And depending on how many patches you have, maybe again and again.
So Powder of Startling Toxicity is a faster, perhaps slightly less painful way of clearing out the backyard of a new house, or for when your needs change and your current trees must go. I'm sure TS would come up for a slightly more over the top comic-tragic animation for the slaughter of multiple trees at once but in the end it would save time (the guilt buff would still happen but it wouldn't matter since you wouldn't need to poison any other trees in your yard) and hopefully lessen the distress that many Glitchen feel every and every time they pop the cork of that little brown bottle of Death.