Giant Hogweed: The Danger Lurking in Your Garden

Design and InstallationGarden Caregarden TriviaIndoor plantsPlant Health CareUncategorized
Written By Peter Morris

Giant Hogweed….and friends

Hogweed

Description

This plant is a biennial herb in the carrot family (Apiaceae). Originating in the Wester Caucasus - they are found throughout the temperate northern hemisphere and in high mountains as far south as Ethiopia.It was introduced into Europe and North America during the Victorian Era as an ornamental – BIG MISTAKE !In New York you can find it particularly in meadows, fields and at the edges of wooded areas. 

Hogweed flowerhead

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Common names for the genus or its species include hogweed, cow parsnip, cartwheel flower, cow parsley, and hog bane. 

sap burns on hand

Poisonous

The sap of giant hogweed is phototoxic and causes phytophotodermatitis in humans. The mix of sap and sunlight on the skin results in severe inflammation, blisters and eventually scars. These serious reactions are due to the compounds in the leaves, roots, stems, flowers, and seeds of the plant. Symptoms begin within 15 minutes of exposure and can last for days. Medical attention is required for severe cases or if sap makes contact with the eyes.

The more sun exposure you have with the sap on your skin - the worse it gets. Children’s more delicate skin is prone to having a very strong reaction. 

Oddly enough - consumption by grazing animals does not appear to cause them harm – sheep, pigs and cattle can eat it without issues. I wouldn’t ! 

Similar looking Plants

Hogweed is in the genus Heracleum – but it is sometimes mistaken for similar looking plants – some of which can be just as, or a bit less toxic than Hogweed. Know your plants ! 

Giant hogweed (Heracleum mantegazzianum)

stem is green with purple spots

Height: 7-14 ‘ tall

Toxicity: This plant can cause burns - Do not touch

Flowers: White umbrella-shaped clusters up to 2.5 ft wide with 50 + rays per cluster. Bloom time: late June - mid July

Leaves: compound, lobed, deeply incised, and up to 5 feet wideStem: green with purple splotches and coarse white hairs.

Stalk: has a thick circle of hairs at base of leaf stalk which is 2-4 “ in diameter 

Cow Parsnip (Heracleum maximum)

not as tall but the same type of flower head

Height: 5 to 8 feet tall

Toxicity: This plant may cause burns – Do not touch

Flowers: White flat-topped flower clusters no longer than one foot wide15-30 rays per cluster

Bloom time: Flowers late May - Late June

Leaves: are compound but less incised than hogweed, and 2 feet wide

Stem: is green and rigid with fine white hairs 

Angelica (Angelica sylvestris)

smooth purple stem

Height: 4 to 9 feet tall

Toxicity: This plant may cause burns – Do not touch

Flowers: Softball-sized and shaped clusters of flowers, greenish-white or white

Bloom time: mid May - mid June

Leaves: Compound leaves extend up to 2 feet wide

Stem: is smooth, waxy purple, 1 to 2.5 inches wide with no hairs 

Wild Parsnip (Pastinaca sativa)

greenish yellow flowers

Height: Up to 5 feet tall

Toxicity: This plant can cause burns - Do not touch

Flowers: Single flower stalk with flat-topped umbel of yellow flower clusters

Bloom time: Flowers late May - early July

Leaves: is compound, with 5 to 15 toothed leaflets, variably lobed, yellowish-green

Stem: is yellowish-green with full length grooves with no hairs or bristles 

Queen Anne's Lace (Daucus carota)

dainty small white flowers on a wild carrot !

Height:1 to 3 feet tall

Toxicity: sap can cause skin irritation or blistering for people with sensitive skin.

Flower: is flat-topped umbel of white flower clusters, 2 to 4 inches wide. The central flower cluster is usually deep purple. When fruiting, the umbel becomes concave and resembles a "bird's nest."

Leaf: is compound, and fern-like.

Stem: is green, covered with bristly hairs 

Poison Hemlock (Conium maculatum)

small dainty flowers on a rounded umbel

Height:4 to 9 feet tall

Toxicity: All parts of this plant are very poisonous – Do not touch or ingest

Flowers: are small and white arranged in numerous flat-topped clusters on all branches

Bloom time: late May - late June

Leaves: are bright green, small and fern-like, and may appear glossy

Stem: is smooth and waxy stem with purple blotches, 1 to 2 inches in diameterIt has no hairs or bristles 

beware the ferny leaves !!

Common Elderberry (Sambucus nigra)

pinkish purple flower spike

black shiny ripe fruit

Height: Shrubs 5 to 12 feet tall Spreads and forms thickets

Toxicity: The leaves, stem, and raw or unripe elderberries contain poisonous substances that produce cyanide. Ripe berries ones can be eaten.

Flowers: are White flat-topped or slightly rounded with clusters at branch ends, 2-6 inches wide.

Fruit: is purple to black in color

Bloom time: Flowers June - July

Leaves: are compound, with 5 to 11 toothed leaflets

Stem: when young is green but woody as older with prominent lenticels (pores)It has no hairs or bristles 

Pokeweed (Phytolacca americana)

upright elongated flower

purple fruit

Height: Up to 10 feet tall

Toxicity: All parts of the plant are poisonous. DO NOT Touch or INGEST

Flowers: are Greenish-white racemes (long floral cluster)

Fruit: is a dark purple berry

Bloom time: Flowers late June - October

Leaves: are Alternate, large, entire leaves – it has no leaflets

Stem: green to red or purplish, smooth, with no hairs or bristles   

Whichever way you call it – it’s toxic !

Oh ! and if you see one in your garden - call us !

PLANT SPECIALISTS

GREENING NEW YORK FOR OVER 53 YEARS !

Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBA

All photographs used with permission @SHUTTERSTOCK

Peter Morris

Peter was born and raised on a beautiful green island in the midst of a tropical rainforest. He was introduced into the world of plants at the age of six when his grandmother, an avid Spanish gardener herself, asked him to help her grow seeds for her pepper garden. He was hooked! By the time he was a teen, he had his own rose and orchid collection numbering in the hundreds. Botany was in his blood, and that is what he set out to study.

His passion brought him to NY in the late seventies to further his education. His tenacity allowed him to work full time at Plant Specialists while he completed a MS in Plant Biology. As a manager at the time he felt unsatisfied with his knowledge of business and business processes. Peter felt compelled to learn, so he then pursued and completed an MBA in Quality Management within a few short years.

Peter’s other passion is teaching. His natural ability is quickly consumed by our staff in all subjects in Botany, Horticulture, and Landscaping. He created an immense reference library of more than 3,500 plants providing an invaluable resource for our staff.

Peter’s breadth of knowledge and wisdom allows him to effectively diagnose the needs of plants. Sometimes just by walking into a garden he can create a prescription that fixes even the hardest issue. He is our Staff Botanist, Diagnostician, and all around Mentor. Recently, he has put his immense knowledge and skills into developing a new department that focuses on Plant Healthcare. As he puts it, “Magic through Science”. The PHC staff that surround him have avidly consumed his teachings. Substantially developing their own plant wisdom, many have taken on difficult plant health issues with spectacular results.

Plant Healthcare has been an instant success with customers! The proper treatment of insects and diseases including Organic methods has made pest control a necessity for every plant. Correcting hormonal imbalances caused by planting in containers or refurbishing soils leached of nutrients by irrigation systems are big challenges PHC has become quite comfortable addressing. The scientific approach to the complex demands of keeping plants healthy in our harsh city environment has made many a customer say WOW!

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