Effectiveness of Removing Fireweed Flowers
Effectiveness of Removing Fireweed Flowers
A field experiment to test the ability of Fireweed (Senecio madagascariensis) to produce seed after flower removal.
Capacity to Deliver
The issue
Fireweed is a highly invasive weed capable of invading pastures and disturbed wilderness areas. It reduces agricultural productivity, is poisonous to livestock and capable of outcompeting and displacing native flora.
Individual plants are able to produce up to 30,000 seeds in a season and when removed from the soil fireweed flowers will continue to form viable seed. This results in fireweed being a difficult and time consuming weed to control by hand due to the need to remove, bag and destroy flower heads.
Many landcarers would likely have heard the suggestion that removing the flowers from the plant will prevent the formation of seeds and remove the need to bag plant material.
The solution
This case study tested three different methods of hand weeding flowering fireweed in order to confirm whether removing the flower heads impacted the plants ability to form seed after removal.
Groups of plants were hand weeded and stored in separate bags, at room temperature, for 8 weeks using the following methods;
- Removed whole and left intact without removing any flowers.
- Plants bunched and flower heads cut off using secateurs at a level to ensure all flowers are removed.
- All individual flowers removed from branches by hand.
The impact
At 8 weeks all three groups showed the vast majority of flowers forming seed, furthermore, the methods that removed flowers showed no discernible reduction in seed formation when compared to plants left whole.
These results suggest that removing fireweed flower heads does not prevent seed formation and that the bagging and appropriate destruction of flowers is critical to controlling this invasive species by hand.
Key facts
- Fireweed will continue to form seed when removed from the soil, even if the flowers are removed from the plant.
- In order to effectively control fireweed using the hand weeding method, all flowers must be bagged, removed and destroyed appropriately.
- Successful management and control of fireweed requires the use of various methods depending on the individual situation. These methods include various pasture and grazing management techniques, chemical control and hand weeding.