Abstract: A hillside planter dam enabling a user to cultivate plants on a sloped or otherwise irregular grade has an overhanging funnel, a lateral sidewall, a trowel portion, and a main axis. The overhanging funnel provides a flared structure suitable for gathering rainfall and directing the flow of said water to the interior of the lateral sidewall. The lateral sidewall defines a retention structure defined concentrically about the main axis, terminating in the trowel portion opposite the overhanging funnel. The trowel portion defines an edged formation tapering from the lateral sidewall towards the main axis, wherein the trowel portion defines a similar overall form to a conventional gardening trowel. In at least one instance, a user may employ the hillside planter dam as both a hand tool and a fixed installation, wherein the overhanging funnel may be used as a handle to affect the placement of the trowel portion.