- This plant has a Plant Risk Evaluator rating of No PRE Rating
This is a plant that goes by several scientific names, including Genista racemosa (an illegitimate name), Cytisus x spachianus, Cytisus racemosus, and more! Common names include sweet broom and Easter broom. Like other broom species, it is a member of the pea family (Fabaceae).
Native to the Canary Islands, sweet broom is an evergreen shrub with upright branches that arch as it matures. It produces fragrant flowers in late spring. It adapts to a wide range of soil and moisture conditions and thrives in poor, infertile soil. Some list this plant as a cross between Genista stenopetala and Genista canariensis, both of which are native to the Canary Islands (Missouri Botanical Garden).
Sweet broom has been touted as a sterile, non-invasive substitute for invasive broom species. Genetic research by Annabelle Kleist and Marie Jesenuik at the Department of Plant Sciences at the University of California, Davis concluded that "a proportion of invasive plants are likely hybrids between "French broom" and a currently sold ornamental plant "sweet broom"" (Kleist & Jasenuik, 2011). The so-called sterility of sweet broom may be the result of self incompatibility because most sweet broom sold is propagated vegetatively, meaning they are one to few clones of each other. Viable seed may not be produced between plants that are so genetically similar. It may be fertile if planted near other related broom species, but this is far from proven. Sweet broom is quite innocuous unless planted near a naturalized population of Genista monspessulana (French broom).
If you want to be cautious, do not plant it if you live in a place where other broom species have invaded wildlands and could possibly hybridize with sweet broom. If you want to be very cautious, use an alternative plant.
Why is this plant not included on the invasive plant list?
Not enough is known about whether this plant is actually hybridizing with French broom (Genista monspessulana), as explained above. Not enough information is available to conduct a valid screen using the Plant Risk Evaluator. A plant must either have a High Risk score from the Plant Risk Evaluator or be on the California Invasive Plant Inventory to be on the plant list. Sweet broom does not meet either of those criteria.
For more information about this plant, please see the following resources:
- Missouri Botanical Garden
- Origins of invasive French broom in California (Kleist, 2010)
- Beautiful but ecologically harmful shrubs get a foothold in California forests, by Jeannette E. Warnert, from the Green Blog
- A molecular phylogenetic analysis of invasive and ornamental brooms and their relationships within the Genistoid legumes. A Kleist, M. Jasenuik/Molecular Phylogenetics and Evolution 61 (2011) 970-977.