The following plants are TOXIC to dogs:  

Sometimes produce diarrhea, vomiting :

Bittersweet Woody
Castor Bean
Daffodil
Delphinium
Fox Glove
Ground Cherry
Indian Turnip
Larkspur
Poke Weed
Skunk Cabbage
Wisteria

Causes rash or irritation after skin contact:

Chrysanthemum
Creeping Fig
Poinsettia
Pop Mum
Spider Mum
Weeping Fig

Irritating: Mouth may become swollen, sore lips, tongue pain:

Arrowhead Vine
Boston Ivy
Caladium
Drunk Cane
Emerald Duke
Pathos
Philodendron
Red Princess

Toxic - may cause vomiting, diarrhea, abdominal pain, cramps. Some can cause tumors, heart and respiratory and/or kidney problems.

Amaryllis
American Yew
Apricot, Almond
Asparagus Fern
Azalea
Balsam Pear
Bird of Paradise
Black Locust
Creeping Charlie
Crown of Thorns
Elephant Ears
English Holly
English Yew
Glocal Ivy
Heart Ivy House
Chestnut Buckeye Tree
Japanese Plum Tree
Mock Orange Tree
Peach, Cherry Trees
Pot Mum
Privet
Spider Mum
Umbrella Plant
Western Yew

Hallucinogens:

Loco Week
Marijuana
Morning Glory
Nutmeg
Periwinkle
Peyote

Cause convulsions:

China Berry
Coriaria
Moon Weed
Water Hemlock

Plants with varied toxic effects:

Buttercup
Dutchman's Breeches
Jasmine
Lupine
Matrimony Vine
May Apple
Mescal Bean
Mushrooms
Onions
Poison Hemlock
Rhubarb
Spinach
Tomato Vine

If your dog starts experiencing any of these symptoms or ate something that they're not supposed to eat… call your veterinarian or poison control immediately.