Any parts of the skin that have been exposed to the oil of the citrus plant should be washed immediately removed using a mild soap and clean water. It is crucial that these plants get a full six to eight hours of direct sunlight every single day. I don't sleep, sleep is for the weak. It makes some cats sedated and others stimulated. American Humane adds, Too much of the fresh plant can overstimulate the central nervous system and cause a cat to injure himself.. Cypress is a tree or shrub. Are lemon trees toxic to pets? Tips to Protect Thyme. First, the bad news: humans can eat lemons, but dogs and cats should be kept away from citrus trees of any kind because they contain essential oils that are toxic to pets. Lemon cypress (Cupressus macrocarpa) is an evergreen tree native to California.