# Banker plant

> A non-crop plant kept in the grow to host harmless alternative prey or pollen, breeding beneficial insects continuously so they are ready when pests arrive.

- Canonical: https://genetixbay.com/knowledge/glossary/banker-plant.html
- Also written: banker plants, banker plant system, open rearing system
- Glossary category: Pests and diseases · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

A banker plant is a non-crop plant placed among or near the crop to support a breeding population of beneficial organisms. The classic system is cereal plants such as barley or wheat infested with bird cherry-oat [aphid](https://genetixbay.com/knowledge/glossary/aphid.md) (*Rhopalosiphum padi*), which feeds only on grasses and cannot attack the crop. [Parasitic wasps](https://genetixbay.com/knowledge/glossary/aphidius.md) such as *Aphidius colemani* breed on those aphids and then hunt crop aphids. Flowering plants that provide pollen support predators such as [Orius](https://genetixbay.com/knowledge/glossary/orius.md).

## In practice

Banker plants make [biocontrol](https://genetixbay.com/knowledge/glossary/biological-control.md) self-sustaining rather than relying on repeated purchases. In cannabis they suit greenhouses and long-running mother rooms more than short sealed indoor runs. They need replacing every few weeks as the cereal ages, and they must be scouted like any crop so they do not become a source of pests. Choose host aphids that cannot use cannabis; the [rice root aphid](https://genetixbay.com/knowledge/glossary/root-aphid.md), for example, also uses grasses and cannabis roots, so not every grass aphid is safe.

## Don't confuse with

- **Trap crop**: a plant that lures pests away from the crop.
- **Companion planting**: a broader garden practice with weaker evidence.

## Related terms

[Aphidius](https://genetixbay.com/knowledge/glossary/aphidius.md), [Orius](https://genetixbay.com/knowledge/glossary/orius.md), [Preventive release](https://genetixbay.com/knowledge/glossary/preventive-release.md), [Biological control](https://genetixbay.com/knowledge/glossary/biological-control.md)

## Read more

- [Aphids on cannabis: species, life tables, population growth and IPM](https://genetixbay.com/knowledge/pests/aphids.md)

## Sources

1. UConn IPM. Aphid Banker Plants. https://ipm-cahnr.media.uconn.edu/wp-content/uploads/sites/3216/2024/08/aphidbankerplants.pdf