Hemlock Water Parsnip Plant Care
Sium cicutarium W.H.Baxter
Updated · Sources · How we source care data
Sium suave, the water parsnip or hemlock waterparsnip, is a perennial wildflower in the family Apiaceae. It is native to many areas of both Asia and North America.
Every 5–7 days
Full sun to part shade
50–80°F
40–70%
At a glance
How do you care for Hemlock Water Parsnip?
Water Hemlock Water Parsnip every 5–7 days, letting the top layer of soil dry out between waterings, and give it full sun to part shade. It prefers temperatures of 50–80°F (10–27°C) and 40–70% humidity. Fertilize it every 6 months during the growing season.
Where Is the Hemlock Water Parsnip Native To?
What Is the Hemlock Water Parsnip?
Hemlock Water Parsnip (Sium cicutarium) belongs to the Apiaceae family within the Sium genus. Hemlock Water Parsnip is native to many areas of both Asia and North America. Hemlock Water Parsnip is also known as Water Parsnip.
Hemlock Water Parsnip displays an upright, clumping perennial growth habit, reaching up to 3 ft tall with a spread of approximately 2 ft. Hemlock Water Parsnip produces small clusters of white or pink flowers in umbels.
Leaf size: approximately 6 inches.
How Often Should You Water a Hemlock Water Parsnip?
Sium cicutarium requires watering every 5–7 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 5–7 days
Let soil partially dry between waterings
What Light Does the Hemlock Water Parsnip Need?
Hemlock Water Parsnip thrives in full sun to part shade.
Light Requirement
Full sun to part shade
What Temperature and Humidity Does the Hemlock Water Parsnip Prefer?
Sium cicutarium grows best at temperatures of 50–80°F. Hemlock Water Parsnip prefers humidity levels of 40–70%.
Temperature
50–80°F
Humidity
40–70%
What Soil Mix Works Best for a Hemlock Water Parsnip?
Rich, well-draining soil with plenty of organic matter. Good drainage is essential for Hemlock Water Parsnip to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Hemlock Water Parsnip?
Feed Hemlock Water Parsnip 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 Hemlock Water Parsnip?
Repot every 1-2 years 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 Hemlock Water Parsnip?
Hemlock Water Parsnip can be propagated through seeds, division. Similar propagation techniques also apply to water parsnip plant care, which shares the same genus.
Is the Hemlock Water Parsnip Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Hemlock Water Parsnip, so we can't confirm whether it is safe for cats and dogs. Keep pets from chewing it as a precaution.
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 Hemlock Water Parsnip?
Hemlock Water Parsnip 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 Hemlock Water Parsnip Need?
Hemlock Water Parsnip grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Hemlock Water Parsnip is native to many areas of both Asia and North America. In cooler regions, grow Hemlock Water Parsnip as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 12a
Keep exploring plants
Hemlock Water Parsnip 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 Sium genus — compare its care with other Sium species on PlantoScan.
Sium is part of the Apiaceae plant family — browse all Apiaceae genera and species.
Hemlock Water Parsnip 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: Sium cicutarium W.H.Baxter, family Apiaceae (first published in Suppl. Hort. Brit. [Loudon] 639, nomen. 1850 ; third additional suppl. to Loudon's Hortus Britannicus published in new ed. [4], cited in IK as 'Hort. Brit. Suppl. iii.'.) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Hemlock Water Parsnip, so we can't confirm whether it is safe for cats and dogs. 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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