Pacific poison oak, commonly known as Toxicodendron diversilobum, is a versatile plant native to the Pacific Northwest region of North America. Its leaves, particularly when they change color in the autumn, have a distinctive look that is easily recognized by many people. In this guide, we will delve into the natural history, ecology, reproduction, and potential risks associated with Pacific poison oak, as well as provide information on how to identify and manage this plant.
Natural History and Habitat
Native to the Pacific Northwest
Pacific poison oak is native to the coast of the Pacific Ocean, from British Columbia in Canada to northernCalifornia in the United States (US). It grows in a wide range of habitats, including mixed evergreen forests, woodlands, chaparral, and riparian areas, from sea level to an altitude of around 1500 meters (5000 feet). The plant is most common below this elevation.
Growth and Leaf Characteristics
Pacific poison oak is a perennial shrub or sometimes a vine that can grow to be 3 to 10 feet tall. Its leaves are composed of three leaflets, each about 1 to nearly 6 inches long, and are alternate on the stem. Initially, the leaves are glossy and reddish, which changes to a dull or shiny green by midsummer, and then they transition to yellow or brilliant red before falling in the fall. This color change is one of the easiest ways to distinguish Pacific poison oak from other related species.
Ecological Importance and Uses
Resilient Species
Despite being ailing to humans due to contact with the plant's urushiol oil, Pacific poison oak plays a vital role in the ecosystem. The树下 provides habitat for several species of birds, insects, and small mammals. One study highlighted the importance of these oak woodlands to the abundance and variety of bird species in the cottonwood/poplar oak woodlands along the Sacramento River in California.
Pioneer Species
Pacific poison oak is a pioneer species, commonly sprouting in areas recently disturbed by fire or human activity. By stabilizing newly disturbed soil, it facilitates the establishment of other plant species, a process known as succession.
Reproduction
Strategies for Propagation
Pacific poison oak has two primary strategies for reproducing: vegetative sprouting from rhizomes and root crowns, and sprouting from seed. The plant blooms from March to June and produces small, greenish-white flowers that mature into oval, greenish-white fruits in the late summer. These fruits persist into the fall and winter.
Dioecious Plant
Pacific poison oak is dioecious, meaning that male and female flowers are produced on different plants. This allows for more efficient pollination and seed production in regions where pollinizers are scarce.
Health Risks and Safety Precautions
Allergenicity
Contact with the urushiol oil from Pacific poison oak can cause a severe allergic reaction in most people, leading to an itchy rash. The oil can also be ingested through the skin and inhaled as smoke. If you think you may have come into contact with the oil, remove your clothing and wash your skin immediately.
Safety Precautions
Given the potential for serious allergic reactions, it is crucial to avoid contact with Pacific poison oak and Western poison-ivy plants. If contact is inevitable, wear heavy gloves, plastic bags, and eye protection, and seek medical attention immediately.
Identifying Poison Oak
Visual Detection
Pacific poison oak can be distinguished from other species by its leaves, which are typically three-lobed with an oval shape. During the autumn, the leaves can change from green to brilliant red, yellow, or scarlet. New leaves may be shiny and reddish.
Managing and Controlling Poison Oak
Mechanical and Cultural Control
机械控制
可以通过挖掘或者手工拔除来移除中毒的根和茎。在湿润的土壤中，根部较容易挖出，但在干燥和硬的土壤中几乎无法工作。可以切断生长在树上的有毒橡树枝条。
除草
通常除草并不是控制中毒橡树的有效方法，除非你频繁重复。切掉植物会让水分暴露，可能会吸引可能的接触者。
在发芽后的最初两个月内，大多数中毒橡树或有毒毛茛种子苗都有了坚实的根系，单靠割除顶部是无法控制的。如果在第一年结束时只有顶端留下了一些幼苗，这些幼苗会持续存在多年，因为只要有能结种子的植株在附近，它们就能存活下来。
一次耕作几乎没有什么作用，但如果进行多次耕作以准备苗床和种植一年或两年的栽培作物，则可以控制中毒橡树。
生物控制
虽然一些动物，如绵羊和山羊，可能会吃掉中毒橡树或有毒毛茛，并可能限制这些植物的数量，但除非它们持续密集地放牧几年，否则这些杂草是不会被消除的，也不会阻止它们的传播。
化学控制
几个常见的灌木管理除草剂可用于控制中毒橡树或有毒毛茛。具体的建议将取决于所涉及的土类型（小林地、商业森林、公共娱乐区等）。请咨询相关资源以获取更详细的信息。有许多产品带有各种商标名称可供用户使用，但这些含有以下活性成分或其混合物的产品可以很好地控制中毒橡树和有毒毛茛：草甘膦、麦草畏、2,4 D、三氯吡氧乙酸酯、甲基磺隆、烯草酮和氨基环己醇。带有一个星号的活性成分是供家庭/非商业用户使用的。
除草剂的施用时间取决于施用方式。对已建立的植株进行叶面处理应该在晚春季或初夏（大多数地区6月）进行，在毒橡树或有毒毛茛叶完全展开之后。任何叶子的再生和漏掉的植株都应该在同一年的秋季重新喷雾，因为在落叶前。除草剂可能在有敏感植物的地方飘散，如果风吹的话，可能还会挥发并在温暖的气候中飘到其他地方。在敏感区域施用时需要小心；只对所需的植物进行施药。
中毒橡树和有毒毛茛也可以通过冬季对较低茎（基部树皮方法）施用除草剂和辅助剂来有效控制，这是在树木落叶和休眠期间进行的，那时很少有其他观赏植物或其他有价值的植物在积极生长，可能会因不小心或意外喷药而受到伤害。同时，叶子脱落的茎提供的可能性更少让施用者接触到植物释放出的油。
由于大多数多年生杂草和不需要的植被，需要多次应用多年才能完全控制。有关更详细的建议和特定的使用率，请参考《太平洋西北部杂草管理手册》。
Resources and References
- 中心疾病控制事实表。有毒植物。
- 格拉德曼(A.C.)2006年。毒橡树皮炎：毒葛、橡树和漆树。荒野与环境医学17(2):120–128。
- 霍华德，珍妮特L. 1994年。毒橡树属。在美国农业部森林服务，落基山研究中心，火科学实验室的火效应信息系统在线。[生产者]。
- 英格里斯(R.J.)2012年。毒橡树属。在美国农业部森林服务，落基山研究中心，火科学实验室的火效应信息系统在线。[生产者]。
- 国家首都中毒控制事实表。毒葛、毒橡树和毒漆树：预防与治疗。
- 普雷瑟(T., M.米勒, 和 A.霍尔廷)。2018年。控制问题杂草。在：帕西尼(E.)编辑。《太平洋西北部杂草管理手册》在线。[在线]。俄勒冈州立大学出版。
关于作者
该文档由Stevefromdodge（创作者）撰写。
