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Cow Parsnip Vs Poison Hemlock: Five Key Differences

If you have seen Cow Parsnip and Poison Hemlock together, you already know they are hard to distinguish due to their similar appearance.

You can differentiate between Cow Parsnip vs. Poison Hemlock plants by looking at their stem as Parsnips have hairy green stems with a purple tint while Hemlocks have hairless, green stems with purple blotches.

Also, the lookalike flowers are not similar if you look closely. Thus, ensure to read till the end so you can tell the difference apart easily.

Cow Parsnip & Poison Hemlock: Similarities

Belonging to the same Carrot family, Cow Parsnip and Poison Hemlock are often mistaken for each other.

They are both biennial herbaceous plants that thrive in similar moist areas like near wetlands and stream banks.

cow parsnip flower with bee on top
Sun exposure after direct skin contact with Cow Parsnip can trigger skin allergies.

The confusion mainly arises from their similar leaf features, lookalike tiny white flowers, and can coexist in the same place.

Both plants feature compound leaves of multiple leaflets in a pinnate or bipinnate fashion.

Cow Parsnip Vs. Poison Hemlock: Differences

With keen eyes and prior knowledge, you can easily distinguish between Cow Parsnip and Poison Hemlock.

Despite the lookalike appearance at first glimpse, they are not the same and have very distinct features.

Here is a categorized vs. table between Cow Parsnip and Poison Hemlock.

FeaturesCow ParsnipPoison Hemlock
Scientific NameHeracleum MaximumConium maculatum
Leaf ColorLight green with matt finishBright to dark green color varying with plant age
Plant Size4-8 feet tall4-6 feet but can grow up to 10 feet tall
Blooming TimeApril to JuneLate Spring, usually June and July
Flower Number15-30 rays in the umbel structured flowers8-16 umbellets per compound umbel
Flower Cluster Spread12 inches across in diameter2-5 inches across in diameter
SmellPleasant smell (a mix of Parsley and Aniseed)Poor, musty, mice-like unpleasant smell
ToxicityThe sap can cause irritation and rashes to the skin as a mildly toxic plantAll parts of the plant is highly toxic that can be lethal to pets, livestock and humans

Now, let us dive deeper into the Cow Parsnip vs Poison Hemlock, shall we?

1. Growth Habit

Cow Parsnip plant grows relatively faster and more rapidly than Poison Hemlock.

In height, mature Parsnip attains 6-8 feet tall, same for wild Parsnips, while Poison Hemlock grows over 10 feet tall, provided with ideal care.

Thereafter, Poison Hemlock is more like a tall herbaceous plant than Cow Parsnip.

2. Foliage Features

Cow Parsnip has much larger light green leaves, while Poison Hemlock has darker green leaves.

Meanwhile, the stems of Cow Parsnips are softly hairy and purplish green, but Poison Hemlock has hairless stems with irregular purple blotches.

cow parsnip leaf vs poison hemslock leaf
Cow Parsnip leaves are larger than the ones of Poison Hemlock.

The leaves of Cow Parsnip are broad and deeply divided, resembling a fern-like structure.

However, Poison Hemlock leaves are finely divided, giving them a smoother appearance, as in Carrot leaves.

3. Flowers

Though both plants produce almost identical white compound flowers, the anatomy behind the plant flowers is very distinct.

For instance, Cow Parsnip flowers have 15-30 umbellets per compound umbel, while Poison Hemlock flowers only have 8-16 umbellets.

Likewise, Parsnip flowers are larger, with a diameter of 12 inches, whereas Hemlock flowers are 2-5 inches wide.

4. Roots

The roots of Cow parsnip are edible and can be eaten after cooking. However, all parts of Poison Hemlock, including the roots, are toxic.

Poison Hemlock bears a long tap root of about 10 inches, and sometimes it bears fibrous roots. In contrast, the roots of Cow parsnips are fleshy, fibrous, or taproots.

Poison Hemlock roots have an unpleasant smell like mouse urine, and Cow Parsnips smell like celery or carrots.

5. Toxicity

As the name suggests, Poison Hemlock is lethal if ingested, whilst Cow Parsnip is mildly toxic.

Toxins like coniine and gamma-conceive are present in Poison Hemlock, which affects the nervous system. Meanwhile, the sap of Cow Parsnip can trigger an allergic reaction and cause rashes or blisters.

Nevertheless, both plants are toxic to humans and pets, so keep contact with the plant minimal.

In an accidental case of ingestion, immediately call the following hotline for medical assistance.

Do you know? Similar looking plant to Cow Parsnip, Wild carrot is mildly toxic. There have been reports of painful irritations or rashes in people who have come into contact with its toxic sap.

5. Spread Nature

Native to North America, Cow Parsnip is not an invasive plant available almost throughout the U.S.

However, Poison Hemlock is an invasive plant that can outcompete their surrounding native plants regarding resources.

Editor’s Note

Be Careful While Handling These Plants!

Both Cow Parsnip and Poison Hemlock are toxic and can induce itchy rashes if you touch them without wearing gloves.

Thus, always wear protective gear if you are working around them. Also, steer clear and do not touch any plants that you can not identify on your own.

All The Best!