With a slight chill in the air these past weeks, I thought it was time to introduce some plants suitable for green roofs that will happily show their full colors in the autumn months. My first pick is Aster oblongifolium. Also known as the aromatic aster, this herbaceous perennial is native to the Central and Eastern United States. This wildflower enjoys full sun exposure and grows best in hardiness zones three through eight. Typically growing one to two feet tall, this plant will take on a more bush appearance when compared to other aster varieties. Taking the size of this wildflower into consideration, this perennial should be chosen for a semi-intensive rooftop garden.
The blooms can start appearing as early as August and last into November. These showy bluish-purple flowers have an amber colored center which commonly attracts birds, bees and butterflies. When crushed, this plant will give out a pleasant balsam-like scent, hence the name, aromatic aster!