The Planters are a highly advanced species responsible for creating gigalife organisms. Although humanity found evidence of their existence early in the Commonwealth Universe Timeline, it did not communicate with the Planters themselves until the events described in A Night Without Stars.
Originally, the Sheldon dynasty encountered gigalife on the planet Cressat. Based on the nature of the flora, the discoverers determined that it must have been designed and hypothesized the existence of an alien species they named the "Planters."
During the events of A Night Without Stars, the duplicate of Paula Myo encountered Planters on the planet Trüb. The Planters appear to be intelligences residing within a nanotechnology dust located on that and possibly other planets. They shape the dust as necessary for their purposes, and arrange the planet into artistic structures when not disturbed.
Largely pacifist, the Planters of Trüb simply let their dust fall into dormancy upon conflict with hostile aliens, but reactivated to communicate with Paula and assisted her in rescuing the humans and Vatni of Bienvenido from the threat of the Fallers.
Gigalife appears as a variety of gigantic plant-like organisms, often appearing as floral structures measuring kilometers wide and tall, supported by complex nanotechnology. Upon discovering the gigalife of Cressat, Nigel and Ozzie ordered a careful, noninvasive analysis. (So as not to annoy the Planters if they were to appear). Although this work took more than a century, it ultimately led to a number of nano-technological advances, including biononics.