Al from Camarillo writes
Annual blue grass is invading my rose bush planters.
Grass Out Max (Clethodim Herbicide) is a great choice for killing annual blue grass (poa annua) in ornamental beds as long as the non-target plants are well established. Per the product label, be sure to use a non-ionic surfactant with at least 80% active ingredient, although crop oil surfactants are not recommended around flowers to prevent sensitivity. Please review the product label before application. If you are only experiencing problems in planters, then you may need to examine whether weeds are coming up from the ground below them, in which case you should move and/or add a barrier under or inside the planters. Transplanting or changing the potting soil would also ensure no new growth of unwanted plants.
Answer last updated on: 01/29/2016