Family: Orobanchaceae
Origin, Description & Uses
Orobanche ramosa (branched broomrape, hemp broomrape) is a leafless, obligate parasitic plant native to Macaronesia, the western and central Mediterranean region, and parts of northeastern tropical Africa. It does not photosynthesize and instead survives by attaching to the roots of host plants, extracting water and nutrients directly from them. It is commonly found in disturbed soils and agricultural areas where suitable host plants are present, and it can parasitize a wide range of herbaceous crops and wild species. The plant is small and inconspicuous aboveground, producing thin stems and small flowers, while spreading primarily through very tiny seeds that can remain viable in soil for many years.
Risks & Threats
Although this species is currently not known to be naturalized in the Hawaiian Islands, it possesses traits that are cause for concern and could detrimentally impact tropical island ecosystems if introduced. As a highly specialized parasitic weed, it can severely reduce agricultural productivity by infesting a variety of crop hosts and is difficult to detect early due to its hidden root-based growth. Its long-lived soil seed bank and ability to spread through contaminated soil, equipment, or agricultural materials make it especially challenging to manage once established. For these reasons, prevention is critical to keep it from being accidentally introduced into the Hawaiian Islands or other vulnerable island ecosystems.
High Risk Traits:
- Prefers temperate climates, but tolerant of tropical climates
- Broad climate suitability
- Widely naturalized
- Agricultural weed
- Other Orobanche species have become invasive
- Obligate parasite
- Prolific seeder
- Hybridizes with other Orobanche species
- Self-compatible
- Annual reproductive lifecycle
- Seeds dispersed by wind, water, machinery, and as a produce contaminant
- Forms a persistent seed bank
Low Risk Traits:
- Does not spread rapidly or aggressively
- Not reported to spread vegetatively
