Rattlebox (Scarlet Wisteria) Sesbania punicea
This small tree with beautiful pea-like red-orange flowers comes with a sting. It is poisonous both to animals and to people if seed or plant parts are ingested. It is taking over riparian areas locally in the American River Parkway in Sacramento County were about $300,000 has been dedicated to its control. Sesbania was first detected in California about ten years ago. This South American native looks very similar to a locust tree but only growing 6-10' tall. It is also called red sesbania and rattlebox. Its four-winged seed pods are typically 3-6" long containing 6-10 bean-like seeds. Dry seed pods tend to stick on the deciduous tree. The seeds in the pod will rattle when the tree is shaken. Seed pods also float when released from the tree adding to the dispersal potential of this exotic invader. It is a very serious pest of wetland and riparian areas in Florida, Georgia and Texas.
Sesbania was first detected in Contra Costa County by Bob Case at the Dow Wetlands in Pittsburg in a feeder channel leading into lower Kirker Creek. This plant is considered a noxious weed in California. It is given a "Q" rating by the California Department of Food & Agriculture and as such is considered to have a high potential for environmental damage by displacing native plants and wildlife.
On June 2nd, 2006 Contra Costa County Department of Agriculture in cooperation with Krist Jensen, the Wetlands Manager for Dow, along with the help of high school volunteers from the Athenian School in Danville began an eradication project on the Sesbania. It was found that the infestation was not only in the feeder channel but also in the lower stretch of Kirker Creek. In total the Sesbania was scattered through an area of ¾ mile in length. Knowing that the seed viability can be as long as 30 years for some members of the legume family all seed pods where removed and destroyed on the plants in the upper two-thirds of the infested stretch. Many of the plants and seed pods in the lower third were silted over by the heavy winter run off this year. The extreme lower stretch of Kirker Creek has a high volume of dense vegetative material that we hope will act as a filter to prevent seed from reaching Suisun Bay. The Athenian School volunteers harvested and bagged the bulk of last years seed pods, 95% of which were still attached to the trees. The Agricultural Department completed the seed pod harvesting job.
All of the plants were growing on the channel or creek banks with some trees growing in the creek itself. It was decided to hand-pull all trees and seedlings possible and to cut and treat those that were too large to pull. Amazingly, we were able to hand-pull with the considerable effort of three people trees up to 2" in diameter. Though careful to not strain our backs we did have one mishap while pulling a tree of this diameter growing in about 8 inches of water in the creek. When the tree trunk was pulled from slightly different angles one of our people was thrown off balance resulting in a slow motion back flop into the creek - no injuries just embarrassment! In all 104 trees were hand-pulled. Only a 10-15% of them were seedlings. Seventy-four trees up to 4" in diameter were cut down and the 2-3" stumps were treated with a mixture of Remedy® (tryclopyr) and horticultural oil. All of these were on the dry creek banks.
As with all noxious weeds success can only be achieved through diligent and persistent long-term follow-up and monitoring. We will hand-pull all new seedlings annually prior to seed pod production until the seed bank is depleted. It very well may be a 20-30 year commitment due to the potential longevity of the seed.