Answer: Unfortunately, I am not aware of anything special you could do except to expose them to some chilling, and that would be pretty tough to do. The acidantheras can be very difficult to rebloom the second year in any case, so their prognosis is not all that great in any case. The dahlias and cannas can be left to limp along as best they can until frost knocks them back and you can dig them. They will do better next year if the weather cooperates, and the longer the season the larger their tubers and rhizomes will be for next year, so it is really better to keep them going as best you can. Having said that, and facing drought myself, I know the feeling of just wanting to throw in the towel on this year and hope for better luck next time. If your emotional attachment and financial investment are not too great, it is always an option to either give them away to another gardener or throw them out. Alternatively, keep in mind that the worst of the heat should be over soon and the fall rains should start and they will thrive on that. Keep watering as best you can, set them in morning sun only so they don't dry out quite so fast, and make sure their containers are large enough to keep their root systems adequately hydrated. Make sure too when you water that you are giving them a good soaking, that the water is going into the soil and not running out between the pot and the soil. If they have gotten really dry sometimes the water just beads up. If this is happeneing, set the container in a pan of water and wait for it to soak up water from the bottom. Then allow it to drain freely so the plant is not left sitting in water. Finally, make sure you are fertilizing them enough. They are heavy feeders, especially so when grown in containers. Use a water soluble fertilizer for blooming plants according to the label instructions. You might also use a kelp or seaweed based nutrient formula and even top dress them with compost periodically. These plants are gorgeous when healthy, and as the weather moderates I would expect them to perk up remarkably. I hope this helps.
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