Scotch Broom
Cytisus scoparius

Name and Family

Scotch broom, Cytisus scoparius, is a member of the legume family (Fabaceae).

History

  • Scotch broom originates from Europe.
  • It was brought to North America as an ornamental garden plant in the 1800s.
  • Alternative uses include
    • a coffee alternative.
    • medicinal uses.
    • a source of yellow dye.
  • Today it has managed to escape from many gardens and is a common invader on both the Pacific and Atlantic coasts.
  • In PEI there have been a few sightings of Scotch broom along roadsides and in ditches. However, most are contained in gardens.

Identification Guide

Here are some distinguishing features that may help to positively identify Scotch broom:

  • Effects and Identifying Features
  • Scotch broom is shrublike, growing from 1-3m tall at maturity.
  • The plant’s trunk is covered in a brown bark, while its stems are green (remaining so throughout the winter).
    • Stems are five-angled.
    • Scotch broom’s green branches periodically die back, turning brown, and may regrow.
  • Leaves are small (0.5-1“ long) and of variable shape.
    • Upper leaves are unstalked and simple.
    • Lower leaves are compound with 2-3 leaflets.
  • In June, the plant produces a huge number of yellow flowers.
  • In July, the plant produces hairy, pea-like seed pods which mature from green to black. Each pod contains 5-12 seeds.
    • The plant spreads by explosive dehiscence, which means that as they mature and dry, they eventually explode, shooting seed.
    • A single mature plant can produce over 3500 seed pods.
  • The plant presents a fire hazard due to high levels of volatile oils.
  • The plant’s distribution is currently limited on PEI. Report any sightings of the plant to the PEIISC via peiinvasives@gmail.com, by direct message on social media, or on iNaturalist.

What it does in the ecosystem

  • Scotch broom grows in open areas, in ditches, meadows and yards. 
  • It competes with native species for available light, nutrients and moisture and has no natural enemies on PEI. 
  • It has a deep and extensive root system so it is very difficult to eradicate once it becomes established. 
  • Scotch broom is a prolific seed producer, with a single plant producing as many as 18,000 seeds annually.
    • Controlling a single plant before seed set can reduce Scotch broom’s spread significantly.
  • The plant contains high levels of oils, making it a significant fire risk.
  • Fortunately, Scotch broom is not yet widespread on PEI so we still have a chance to eradicate it or prevent further spread.

Management

GENERAL CONSIDERATIONS

  • As Scotch broom is not yet widespread on PEI, eradication is a realistic possibility. 
  • If you are aware of any Scotch broom infestations on PEI, we encourage you to report them to us on EDDMapS at www.eddmaps.com or at peiinvasives@gmail.com. 
  • Early detection is key to preventing the spread of this nasty invasive, and we can’t do it without your help!
  • Before selecting a control method, consider the size of the infestation, your available resources, and the amount of effort you are willing to expend. 
  • Often, multiple control methods are used simultaneously. 
  • Consider the local ecosystem and what other organisms or ecological processes may be affected by management. 
  • Management should take place early in the season before seed set. (Seeds are set during July – August).

DIGGING/PULLING 

  • Smaller plants can be hand-pulled in loose soils, but larger plants will require digging.
  • Digging is a labour-intensive method for removing Scotch broom, therefore it may not be the best option for large-scale infestations. 
  • Shovels or weed wrenches can be used to remove as much of the plant and root system as possible. 
  • Any digging of Scotch broom should occur before the plant goes to seed, to prevent further spread. 
  • As much of the root should be removed as possible, to prevent shoots from growing. 
  • Digging will disturb the soil and promote germination from the seed bank, making site monitoring necessary. Limit soil disturbance where possible. 

CUTTING AND COVERING 

  • Cutting of Scotch broom produces mixed results and is most successful when combined with covering techniques. 
  • Cutting should occur before plants go to seed and preferably during the summer when precipitation is low. 
  • Cutting during flower but before seed set ensures that most of the plant’s energy is in its aboveground parts, leaving little energy for the roots to work with after cutting. 
  • Plants should be cut down to ground level. 
  • The remaining stump should then be covered in two layers of thick black plastic. The thicker and darker-coloured the better.
  • This covering is intended to prevent any regrowth that may occur at the cut stump from obtaining the light it needs to grow. 
  • Secure the tarp with debris, bury it, or use landscape staples to secure the edges. 
  • Return to the site regularly to ensure no regrowth is occurring and that the tarp is still properly secured. 
  • Some regrowth may occur, but the opaque plastic blocks light and inhibits growth so the plant should eventually die. 
  • 100% mortality should be reached within two years. 

CHEMICAL CONTROL 

  • The Prince Edward Island Invasive Species Council does not offer recommendations for chemical control as a management technique at this time.
  • If chemical control is used, product labels should be strictly followed and considerations for possible environmental damage should be taken into account. 
  • The use of herbicides is prohibited near watercourses and wetland environments in PEI. Please visit https://www.princeedwardisland.ca/en/topic/pesticide-use-and-regulation to learn more about provincial regulations on pesticide usage. 

Disposal, Follow-up, and remediation

  • After work is completed, it is imperative that all equipment be thoroughly cleaned and that all plant parts are removed from boots and clothing before leaving the area. 
  • If the plants have fruit, All branches with seed pods must be bagged and properly disposed of.
    • Bag the plant material in clear plastic bags.
    • Mark the bags boldly with a permanent marker. Write “INVASIVE PLANT” or “SCOTCH BROOM” on the bags. 
    • If the bags are thin, double bag them to prevent accidental dispersal later on.
    • Tie the bags tightly and place them in your usual residential waste collection (THE BLACK BIN)
    • Never place invasive plants into the compost. This may allow them to become established once they reach the heap. 
  • If management occurs before seeds are formed, or if the plants have not yet matured to produce seeds, the most important thing is that the roots of the plant are left in such a way that they cannot root themselves back in the soil.
    • Place plants in a dry location where their roots are not in close contact with the ground. 
    • The PEIISC often hangs buckthorn plants upside down by their roots from nearby trees. 
    • Alternatively, pile the plants on the ground and return to “turn” the pile, preventing rerooting.
  • With any management tactic, it is important not to let any Scotch broom regrow after management efforts. 
  • Return to the site at least every year to treat any new growth that may arise. 
  • Scotch broom has an exceptionally robust seed bank, with seeds that can persist in the environment for up to 80 years! 
  • Replanting the area with native plants after management is a great way to promote habitat regeneration and give any new Scotch broom plants that arise at the site some competition.
  • Plant material may also be burned at your own risk, taking into account all necessary precautions to ensure safe burning.
    • Review local regulations and permitting requirements before conducting any burning to ensure that your burn falls within the limitations of the law. 

Map

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References

Metro Vancouver Scotch Broom Best Management Practices

BroomBusters – Cut Broom in Bloom, Mid-Vancouver Island BC

Scotch broom – Invasive Species Council of British Columbia (bcinvasives.ca)

NCC: Scotch broom (natureconservancy.ca)

Scotch Broom | National Invasive Species Information Center