Poison Hemlock Plant Care
Conium maculatum L.
Updated · Sources · How we source care data
Conium maculatum, commonly known as hemlock or poison hemlock, is a highly poisonous flowering plant and a nitrophile weed species in the carrot family Apiaceae.
Every 7–14 days
Full sun to partial shade
50–80°F
40–70%
At a glance
How do you care for Poison Hemlock?
Water Poison Hemlock every 7–14 days, letting the top layer of soil dry out between waterings, and give it full sun to partial shade. It prefers temperatures of 50–80°F (10–27°C) and 40–70% humidity. Fertilize it every 6 months during the growing season. It is reported as toxic to pets, so keep it out of reach of pets.
What Is the Poison Hemlock?
Poison Hemlock (Conium maculatum) belongs to the Apiaceae family within the Conium genus. Poison Hemlock is also known as Hemlock, Spotted Hemlock, Wag-behind.
Poison Hemlock displays a tall, erect biennial growth habit, reaching up to 6 ft tall with a spread of approximately 2 ft. Poison Hemlock produces small white flowers arranged in compound umbels.
Leaf size: approximately 6 inches.
How Often Should You Water a Poison Hemlock?
Conium maculatum requires watering every 7–14 days. Allow the top layer of soil to dry between waterings to prevent root rot. Reduce watering frequency during winter when growth slows.
Watering Frequency
Every 7–14 days
Let soil partially dry between waterings
What Light Does the Poison Hemlock Need?
Poison Hemlock thrives in full sun to partial shade.
Light Requirement
Full sun to partial shade
What Temperature and Humidity Does the Poison Hemlock Prefer?
Conium maculatum grows best at temperatures of 50–80°F. Poison Hemlock prefers humidity levels of 40–70%.
Temperature
50–80°F
Humidity
40–70%
What Soil Mix Works Best for a Poison Hemlock?
Well-draining sandy loam with added organic matter. Good drainage is essential for Poison Hemlock to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Poison Hemlock?
Feed Poison Hemlock every 6 months during the growing season (spring and summer) with a balanced fertilizer diluted to the strength on the label.
Pause feeding in autumn and winter, when growth slows, and never fertilize dry soil — water first.
Fertilizing
Every 6 months
During the growing season
The PlantoScan app can remind you when to water and when to fertilize each plant.
How Do You Repot a Poison Hemlock?
Repot annually in early spring. Choose a pot one size larger than the current container, and ensure it has drainage holes to allow excess water to escape.
How Do You Propagate a Poison Hemlock?
Poison Hemlock can be propagated through seeds. Similar propagation techniques also apply to yellow hemlock plant care, which shares the same genus.
Is the Poison Hemlock Toxic to Pets and Children?
Toxic (caution)
Reported as toxic in our plant data. Not verified by the ASPCA.
This is a general caution, not veterinary or medical advice. If your pet ate a plant, contact your vet or animal poison control.
See all plants toxic to cats and plants toxic to dogs.
What Pests and Diseases Affect the Poison Hemlock?
Poison Hemlock is susceptible to aphids, caterpillars, spider mites. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.
Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.
What USDA Hardiness Zone Does the Poison Hemlock Need?
Poison Hemlock grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. In cooler regions, grow Poison Hemlock as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 12a
Keep exploring plants
Poison Hemlock is one of many species covered in the complete plant care and identification guide, which groups plants by genus, attribute, and popularity.
It belongs to the Conium genus — compare its care with other Conium species on PlantoScan.
Conium is part of the Apiaceae plant family — browse all Apiaceae genera and species.
Poison Hemlock thrives in bright light and direct sun — see other bright-light plants.
Related Plant Care Guides
Closely related plants with similar care requirements:
Sources
- Scientific name & taxonomy: Conium maculatum L., family Apiaceae (first published in Sp. Pl. : 243 (1753)) — World Flora Online record, IPNI name record.
- Pet toxicity: Poison Hemlock is reported as toxic to pets in our plant data (not verified by the ASPCA), so treat it with caution. Checked against the ASPCA plant list; any other toxicity note on this page comes from PlantoScan's plant database.
- Hardiness zone: USDA Zone 12a, calculated from the plant's minimum temperature.
- Care values(watering, light, temperature, humidity, soil, fertilizing): PlantoScan's plant database, filtered by automatic plausibility checks — values that fail them are hidden. How we source and check plant data.
Spotted a mistake? Email info@upvision.media with the page link — we check and correct reported errors.
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