Thinking about taking a hike in local Southern California parks or mountains? Smart hikers will want to be aware that all plants that are called “natural” is not safe to eat. In Southern California alone, there are 17 known deadly plants that you should never eat. Here are five of the most common of those poisonous plants.

1.) Oleander

According to rodalesorganiclife.com.One of the most poisonous plants known, this evergreen shrub is commonly grown throughout warmer areas of the U.S. In California, it’s even grown along roadsides and used to decorate highway medians because it is drought tolerant and wildlife will not consume it.

The showy and often fragrant flowers make this a popular ornamental for backyard landscapes, but care must be used to keep children and animals from eating any part of the plant because the whole plant is poisonous. Ingesting even a small amount of the leaves can be lethal, or cause severe gastrointestinal and cardiac reactions.

2.) Apple Seeds

According to MNN.com, apple seeds contain a small dose of cyanogenic glycosides, which is making them mildly poisonous. But to get enough of the cyanogenic glycosides to kill you need to eat roughly 200 apple seeds, or about 20 apple cores, so there is nothing to worry about.

3.) Deadly Nightshade

Berries of this plant are extremely toxic. Deadly nightshade has a long, colorful history of use as a poison, but what many people don’t realize is that the nightshade family includes common food plants, including potatoes, tomatoes, eggplants and chili peppers stated rodalesorganiclife.com.

4.) Rosary pea

“Rosary peas got their name from their traditional use as ornamental beads for rosaries. They are used in jewelry around the world. Many jewelry makers have died after pricking a finger while handling a rosary pea. The poison contained within the seed is abrin a close relative of ricin and one of the most fatal toxins on Earth,” reported MNN.com.

5.) Castor Beans  

If you have consumed castor oil before, you might be surprised to learn that the castor bean contains one of the most poisonous substances in the world, ricin. Consuming just one castor bean will be enough ricin to kill an adult within a few minutes. Even though the castor bean is highly poisonous, castor bean plants are frequently grown for decorative purposes, even in parks and public places.

So perhaps the best advice for novice hikers is to enjoy nature but select your produce from the supermarket.