Washington State poisonous plants can be a real hazard if you can’t identify them.

Washington State Poisonous Plants

Although some add ornamental value to your garden, others should be quickly removed – like poison hemlock.

You should also be able to identify these plants to avoid them during your outdoor hikes and strolls.

Toxic Plants To Identify in Washington State

1. Poison Hemlock

Deadly Poison Hemlock Plant

Distinguishing characteristics 
  • When it’s one year old, the plant grows a large rosette of basal lacy leaves on hairless stems. 
  • In its second year, the plant grows a tall flowering hollow purplish stalk that measures about 10 feet tall. 
  • Many native plants might resemble Conium maculatum and confuse you if you aren’t familiar with the plant. American elderberry, common ragweed, and common yarrow can all look like this plant. 
Care requirements
  • This plant isn’t picky about its location but prefers growing in full sun and partial shade like bracken fern
  • You can see it growing along roadsides, undisturbed cleared woodlands, ditches, and meadows.
  • Every part is highly toxic. 
  • It’s believed to be one of the most poisonous plants for dogs in Washington State.
  • Small colonies of this plant can be hand removed. However, wearing gloves is crucial to protect yourself from toxicity symptoms. 
  • Plant parts remain poisonous after removal, so they should be burned. 

This plant is native to Asia and North Africa but was introduced as an ornamental plant to the US in the early 1800s.

Despite being highly toxic to animals and humans, it has naturalized in most American states, becoming an invasive landscape plant. 

2. Common Foxglove

Ornamental Common Foxglove

Distinguishing characteristics 
  • Can be 5 feet tall and grows eye-catching tubular blooms. They appear in early summer in red, purple, white, or yellow shades.
  • Prone to aphid, mealy bug, and Japanese beetle attacks. 
  • Most mild infestations are handled by predatory insects, although using insecticidal soap will be able to tackle more severe infestations.
Care requirements
  • Most cultivars bloom in their second year, but some can start blooming in their first year. 
  • Grows in rich, moist soil and can tolerate full sun to partial shade.
  • Ingesting leads to symptoms like dizziness, vomiting, irregular heartbeats, and even sudden death in humans.
  • Animals that eat 0.05% of their body weight can be poisoned. So if you keep any on your property, you should avoid growing this plant.
  • If you have kids or animals that can get in contact with this flowering plant, then it’s best to remove it by cutting off the stalks and digging up the roots. 
  • New plants might appear, so you need to dig them out until you’ve completely got rid of this plant. This can continue for a whole season. 

This attractive plant freely self-seeds, creating a flowering patch that appears every year in your garden. Although it can make a beautiful hedge, it’s not that popular because of its invasive and toxic traits. 

3. Poison Ivy

Rash Inducing Poison Ivy Vine

Distinguishing characteristics 
  • Identifying the Toxicodendron radicans depends on its maturity. The plant has red leaves when it’s young, and the oil on the leaves and stems can rub on your clothes and shoes. 
  • Mature plants become green, and the foliage turns to gorgeous shades of orange and red in the fall.
  • Grows non-showy white flowers with orange centers. Then they turn into yellow berries, which are also toxic. 
Care requirements
  • This plant isn’t picky about soil and light conditions, making it a successful weed. 
  • Grows with the Virginia Creeper, but you can tell both plants are apart.
  • Symptoms of toxicity of this plant show within 8 to 48 hours after contact. 
  • Touching this plant usually leads to a painful rash, swelling, and blisters. 
  • Inhaling the fumes of burning poison ivy can lead to breathing difficulties. 
  • Removing this plan manually will work, as long as you wear gloves and ensure it doesn’t get in contact with your skin. 
  • Since burning the plant can lead to severe symptoms, you can get rid of it by pouring boiling water over the leaves and roots. 

This weed can be found in urban landscapes competing with your garden plants for nutrients and water.

Removing this plant on a dry day with no wind is the safest option. After that, you must clean your shoes and clothes thoroughly to avoid skin rashes. 

4. Poison Oak 

Poison Oak Shrub

Distinguishing characteristics 
  • Every leaf is made of three leaflets and can be about six inches tall. Some leaves can be equally lobed, like the leaves of an oak tree, which explains the plant’s common name.
  • New plants are reddish and covered in toxic oil, and the white flowers grow in late spring. Then, they turn into waxy white berries.
  • Several butterflies and moths will feed on the leaves of the poison oak in Washington State. The leaves contain large amounts of calcium and phosphorus that nourish animals like squirrels and deer. Robins and other songbirds feed on the berries. 
Care requirements
  • It grows as a shrub in open areas and as a vine in shaded areas. 
  • This plant can be 6 feet tall, with an upright growth pattern like sticks. When the plant loses its leaves, it becomes more difficult to identify. 
  • The oil of this plant causes rashes and other allergic reactions. 
  • Applying rubbing alcohol or a degreasing dishwashing detergent can help relieve pain. 
  • You can manually remove the plant by digging out the roots. You can also cover it with impervious material that prevents it from growing. 
  • Herbicides that contain glyphosate and triclopyr are potent at getting rid of this plant.

This is not an oak tree but a deciduous shrub that might grow slowly in your garden. Herbicides work better when applied late in the season when the leaves are still green. Burning this plant will release toxic oils into the air. 

5. Giant Hogweed

Towering Giant Hogweed Plant

Distinguishing characteristics 
  • This plant is an invasive weed that shouldn’t be left in your garden because it can stunt the growth of nearby plants. 
  • Every part of this plant justifies why it’s called a giant plant. It has compound leaves that can be about 5 feet wide and long hollow stalks that can be 4 inches in diameter.
  •  Flower clusters can be about 2 feet wide. They’re made of white blooms that appear in summer. 
Care requirements
  • The seeds are set in August, and the plant becomes ready to spread. 
  • It takes about four years to reach its mature size.
  • The sap of this plant causes light sensitivity. It inhibits your skin from protecting itself from the sun. 
  • Painful blisters form when the skin is exposed to sunlight, turning into scars that look like burns. 
  • The sap can also cause temporary or permanent blindness if it gets into the eyes. 
  • Wear gloves while removing this plant and ensure that it won’t get in touch with your skin. 
  • It’s best to dig out the roots, using a tool that tilts the soil to make sure that you’ve got rid of every part. You might have to do this for several seasons. 

Also known as giant cow parsnip, this plant can grow to a height of 20 feet. The plant is originally native to Asia and spread into the US wilderness after being introduced as an ornamental plant. Transporting this plant across states is illegal. 

6. Stinging Nettle

Stinging Nettle Herb

Distinguishing characteristics 
  • The Urtica dioica is a fast-growing perennial. Depending on the plant’s status, it can be considered a weed, or you can grow it as an ornamental plant in your garden.
  • This plant is a food source for various butterfly and moth caterpillars. 
  • Some people also cook the leaves, as they contain vitamins A and C and other healthy nutrients. 
Care requirements
  • Also known as burning grass, this plant is easy to grow and isn’t prone to many pests and diseases. 
  • You can divide the plant and grow the roots. You can also grow the seeds indoors and sow them before the last frost.
  • Thrives in nitrogen-rich soil and prefers disturbed soil, where other plants struggle to grow.
  • Although the leaves taste a little like spinach, they should be consumed in moderation.
  • The leaves and stems of this plant are covered in tiny hairs. These hairs produce a chemical that causes a burning sensation when touched. 
  • Removing flowers as they appear can help you control the spreading of this plant, as you prevent it from self-seeding. 
  • Regular harvesting of the edible leaves will also keep the plant under control. People use the leaves to make nitrogen-rich compost. 

If you identify this plant and know how to handle it, you’ll be able to grow it in your garden safely. It reaches its mature size by mid-season and survives for several years growing from rhizomes. In summer, it grows white-green flowers. 

7. Japanese Yew

Toxic Japanese Yew Tree

Distinguishing characteristics 
  • This shrub can grow to reach a height of 30 feet, although it reaches a height of 50 feet in its native habitat. 
  • Homeowners grow this plant because of its attractive spiny needles and ornamental red fruits. 
  • It’s usually pruned to maintain its shape. The bark is reddish, and in the fall, the green foliage turns into a similar shade of reddish-brown.
Care requirements
  • Grows in medium-moisture well-draining soil but can be drought-tolerant. 
  • Tolerates various light conditions, including full shade.
  • You can grow it as a hedge or as a foundation plant. It’s versatile, so you can keep it pyramid-like, broad, or flat-topped.
  • Yew seeds, leaves, and fruits are toxic to humans and pets. 
  • It’s deadly to horses and livestock, so you should avoid it if you have animals on your property.
  • Always wear protective gloves while dealing with this plant. 
  • Since the roots can be about 16 inches deep, you need to cut the stems and dig soil around the roots to remove them efficiently. 

This evergreen shrub is native to Asia and is considered an invasive species in the northeastern regions of the US. It’s also known as the spreading yew and is usually grown as an ornamental plant, as it responds well to pruning. 

8. Queen Anne’s Lace

Delicate Queen Annes Lace

Distinguishing characteristics 
  • Grows to a height between 2 and 3 feet. 
  • Has fern-like foliage and clusters of pretty tiny white flowers that give this plant its lace-like appearance. There’s usually a purple flower in the middle of each group.
  • The plant is named after Queen Anne of England, an expert at making lace. Some people also call it wild carrot because people used its fruit in the past as a substitute for carrots in cooking. 
Care requirements
  • This plant is pretty easy to grow. However, you need to provide it with enough space to spread and grow it in full sun. 
  • The wild carrot plant thrives in poor, dry soil where other plants might struggle to grow. 
  • Needs regular watering until it gets established.
  • Compared to other toxic weeds Washington State, this is less dangerous. It can harm people who have sensitive skin, though. And it looks a lot like more toxic plants like cow parsnip, so it’s best to avoid it.
  • The edible taproot of this plant looks a lot like the taproot of the poison hemlock, which is highly toxic. 
  • Before the plant sets seeds, you can mow it to control its growth in your garden. Without flowers, the plant will eventually die. 
  • Hand-pulling the plants also works, but you must dig out the roots to prevent young plants from growing in your garden. 

This wildflower herb can be found in Washington State, where it can live up to 5 years. Although it’s a great addition to your wildflower garden, it’s usually considered invasive.

If regular removal methods don’t work, you’ll have to use a herbicide since a single plant can produce up to 40,000 seeds. 

9. Common Butterbur

Soothing Common Butterbur Plant

Distinguishing characteristics 
  • Has heart-shaped green leaves with flowering stalks and tiny pink flowers that bloom in clusters. 
  •  Grows as a short shrub, reaching a height of 3 feet tall and a width of 5 feet. 
  • The leaves are wooly on the underside, and several variegated varieties grow green and cream leaves.
Care requirements
  • An excellent choice for woodland and rain gardens, where it thrives in moist locations. This makes it a great plant to grow around water features in your garden.
  • The common butterbur is pretty easy to take care of and isn’t prone to many diseases or pests.
  • Thrives in different types of soil and will tolerate various light conditions.
  • This plant is toxic to people and animals. Moreover, it grows from rhizomes, so it can quickly spread in your garden.
  • Ingesting different parts of the plant can lead to an upset stomach, dizziness, headache, and increased bleeding tendency. 
  • Mowing won’t remove this plant from your land but will prevent it from spreading. 
  • The best way to get rid of this plant is to remove it by hand-pulling. 

Also known as devil’s hat and bog rhubarb, this plant is usually grown for its luscious foliage, although it’s toxic to people and animals.

Various cultivars are widely used in landscape designs, including Fuki, which has larger leaves than common butterbur and yellow-white flowers. White butterbur grows white bloom clusters in the spring. 

10. Poison Sumac

Poison Sumac Shrub

Distinguishing characteristics 
  • Most sumac plants aren’t harmful, except for this one. It grows an odd number of leaves, usually between 7 and 13. 
  • The middle part of the leaf is a lighter color, and the stems are red. 
  • The oddly-shaped berries grow in the summer, and the foliage turns orange, pink, or red in the fall.
Care requirements
  • It’s essential to identify and remove this plant because it has a lot of harmless lookalikes that you can easily incorporate into your landscape design. 
  • Thrives in wetlands and saturated soils, with full sun to partial shade. 
  • All parts, especially the berries, are toxic to humans. But they’re not toxic to birds that this shrub attracts. 
  • The plant’s oil causes a skin allergic reaction. The rash can last for weeks. 
  • To get rid of this plant, you need to cut it to a foot long or so and then apply a non-selective herbicide. 
  • Mowing any root sprouts will prevent this plant from spreading in the future. 

This moisture-loving shrub grows in wetlands. It’s native to the US, so it won’t upset the natural balance in your garden, but due to its toxic traits, many homeowners choose to remove it.

After removing this plant, you should wash your clothes and hose your boots thoroughly to guarantee that the toxic substances won’t get in contact with your skin. 

11. Belladonna

Deadly Belladonna Nightshade

Distinguishing characteristics 
  • Can be about 4 feet tall and wide. 
  • Features dark green leaves that measure between 3 and 10 inches long and grow in pairs on the top part of the plant.
  • In the summer and fall, this plant grows purple-green-tinged mildly scented flowers. The flowers then turn into a fruit called the devil’s cherry.
Care requirements
  • Belladonna prefers to grow in moist soil and partial shade. However, moisture is essential for this plant.
  • Grows like a weed, dies, and reappears in your garden. Birds eat the seeds and leave them in their droppings, allowing the plant to grow in different locations.
  • The belladonna’s berries resemble wild, black, and blueberries. However, you should avoid them because they’re highly toxic.
  • The berries taste sweet when you take the first bite, but eating two berries can kill a child, and about 20 berries to kill an adult.
  • It’s essential to wear long gloves to protect your skin from contact when handling this plant in your garden. You can also wear goggles if the plant is tall enough to come in contact with your face.
  • Dig out all the roots, as new plants will easily emerge if you leave any roots in the soil. 
  • You can also apply glyphosate or any other non-selective herbicide, especially if the plants are still young. 
  • Disinfect any tools you used to remove this plant from your garden to prevent future contact. 

Known as the deadly nightshade, this plant should never be allowed to grow in your garden.

The plant’s common name relates to an ancient habit where Italian women used eye drops made of this plant to widen their eye pupils. Honeybees that feed on this plant produce honey, which is also toxic to humans. 


Identifying the toxic plants in Washington State and the pacific northwest region can save your life if you encounter any of them.

It will also help you identify the unwanted species in your garden to keep it safe.

  • Some toxic plants, like poison oak, are harmful to people but won’t harm animals or birds.
  • Plants like spreading yew and foxgloves are highly toxic to animals.
  • Some plants, like common foxglove and Queen Anne’s lace, are toxic but will represent an attractive addition to your garden.
  • Plants like belladonna can kill people quickly.

With this advice, your garden will be safe for everyone. 




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