It’s impossible to give an exact timeline for how long plants will take to grow in an AeroGarden. This really depends on the type of herbs that you’re growing in your device. For the most part, you should be able to see germination in less than 14 days, though some plants might germinate in as little as 7 days. Within 4 to 6 weeks, you might be able to harvest some herbs and plants. When it comes to how long you can keep plants in your AeroGarden, there is somewhat of a time limit. Six months is probably the upper end.