Well, the plants you bought were grown from seed, so it sounds encouraging. Typically annuals have a short life. They're genetically constructed that way. Their life can be lengthened by growing in certain climactic conditions. Some annual flowers have longer lives than other annual flowers. Marigolds and zinnias keep on growing and flowering until a hard frost here, provided they are deadheaded on a regular basis. Flowering for annuals indicates to the plant that it's time to die, because to flower and set seed is the main point of its purpose.
