Poison oak is similar to its close relatives poison ivy and poison sumac because they are all members of the same botanical family. The most common type of poison oak, known as western poison oak, grows most commonly along the Pacific coast in Oregon, Washington, and California. It can grow as a small shrub in open spaces or as a climbing vine in shaded forest areas. Other varieties of poison oak include Atlantic poison oak, which grows in the southeast US. This variety is much less common than the western poison oak. A good way to avoid a poison oak rash is to never touch a plant that you think may be poison oak.  In order to get close enough to the plant to identify it, use a stick or a gloved hand to examine it more closely. If it turns out to be poison oak, make sure anything that has come into contact with the plant is washed with soap and water. Poison oak, whether it is growing as a shrub or a climbing vine, has a trifoliate leaf structure. This means that the leaves grow in sets of threes off the stem. The edges of the leaves have a wavy or scalloped appearance. As the name suggests, the leaves look a bit like oak leaves. The top side of the leaves are typically a glossy green color. They can also be yellowish, reddish, or brownish depending on the health of the plant and the season. On the underside of the leaf, there is less sheen, less green, and more of a velvety appearance. Stems tend to be a bit greyish in color, though, given the lighting in some forested areas, this can be difficult to see. The stems will also be covered in tiny hair or thorn-like structures. Poison oak has yellowish-green small flowers in the spring. The plant will also produce light green berries throughout the summer and into the fall. This will help you rule out other plants by noting what it doesn’t have. If it doesn’t have pointed leaves and it doesn’t have thorns, it isn’t poison oak. In the winter, it loses its leaves and looks like reddish-brown sticks (sometimes a few poking up from the ground, sometimes a big clump)...

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Write a summary of the previous text in Chinese:
了解毒栎。 研究毒栎时要小心。 观察叶子。 检查颜色。 检查枝干。 注意花或浆果。 了解毒栎的其他形态。