new to gardening; planted several cosmos in planters, 3 or so plants per planter. Plants now turning brown and dying; leaves are “crisp” and crumble when touched and stem is hollow? Google suggests bacterial disease. What is happening and can I do anything now or for future, anything to do differently? thanks v. much
I also have this problem with my container cosmos this year. They like hot weather and poor soil. Implies dry soil. I feel that I over watered since I planted them around the base of a hibiscus which likes water. Might you have over watered? Damp soil can increase bacterial activity.
Cosmos likes to be deadheaded frequently to make it flower more. Hate to say summer is nearly over but for this year, cut back and see if it regrows.
I recommend for next summer. New soil but not rich potting soil. Decrease watering and do frequent deadheading. Hopefully they were planted in a sunny spot. When they are well tended you might see self seeding around your garden.