Planting gardens to support insect pollinators.

Global insect pollinator declines have prompted habitat restoration efforts, including pollinator-friendly gardening. Gardens can provide nectar and pollen for adult insects, and offer reproductive resources such as nesting sites and caterpillar host plants. Here we conduct a review and meta-analysis to examine how decisions made by gardeners on plant selection and garden maintenance influence pollinator survival, abundance, and diversity. We also discuss characteristics of surrounding landscapes and the impacts of pollinator natural enemies. Results from our meta-analysis indicate that pollinators respond positively to plant species diversity, woody vegetation, garden size and sun exposure, and negatively to the separation of garden habitats from natural sites. Within-garden features more strongly influenced pollinators than surrounding landscape factors. Growing interest in gardening for pollinators highlights the need to better understand how gardens contribute to pollinator conservation, and how some garden characteristics can enhance the attractiveness and usefulness of garden habitat to pollinators. Further studies examining pollinator reproduction, resource acquisition, and natural enemies in gardens, and comparing gardens to other restoration efforts and to natural habitats, are needed to increase the value of human-made habitats for pollinators. Article impact statement: Gardens with high plant species diversity and sun exposure, more woody vegetation, and larger size benefit pollinators. This article is protected by copyright. All rights reserved.