Finally, there is a type of cutting back that has nothing to do with removing old flowers or leaves. Some plants, especially fall bloomers, will grow tall and gangly and not be able to support themselves. This photo show New England Asters that are growing tall, but not filling out. Once these plants set flowers they will fall over. To encourage the plants to become stockier, cut the plant by 1/3 once it has reached about 6-8 inches in height. This should cause it to send out more stems. Let it grow about a month and then cut it back by 1/3 again. Now your plant should grow into a full, stocky plant with multiple stems and multiple blooms. The flowers may be a bit later than if you hadn't cut, but there will be more.