Mark, I would say to try foliar spraying them instead of watering with it. It is done by many rose/garden people. Try a 1/2 tablespoon per gallon foliar spray one time and then again 7-10 days later. Using epson salts in soil can change the soils ph. So I would stick to a foliar spray , also it is highly soluble so it makes an exellent foliar spray. Also when You foliar spray you will know that your plants will have "instant access" to the epson salts micro-nutrients. I should have told you this when I recommended epson salts but didnt even think to mention it. Well now you know! Hope it helps.