Answer: Plant marigold seeds in april and begonias in may. Both plants should be up and growing in 2-3 weeks. If you used vegetation killer and it didn't kill off the weeds, you may not have thoroughly sprayed them. Try again in late summer or early fall. This is when plants are doubling their efforts to transport carbohydrates from the leaves to the roots to store over the winter months. If you dose them with Round Up at that time, the herbicide is sure to be translocated into the root system and kill off the roots.
Good luck with your garden.
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