Swamp Loosestrife Plant Care
Decodon verticillatus (L.) Elliott
Updated · Sources · How we source care data
Decodon verticillatus, the sole living species in the genus Decodon, is a flowering plant in the family Lythraceae. It is commonly known as waterwillow or swamp loosestrife.
Every 2–4 days
Full sun to part shade
60–80°F
50–80%
At a glance
How do you care for Swamp Loosestrife?
Water Swamp Loosestrife every 2–4 days, letting the top layer of soil dry out between waterings, and give it full sun to part shade. It prefers temperatures of 60–80°F (16–27°C) and 50–80% humidity. Fertilize it every 6 months during the growing season.
Where Is the Swamp Loosestrife Native To?
What Is the Swamp Loosestrife?
Swamp Loosestrife (Decodon verticillatus) belongs to the Lythraceae family within the Decodon genus. Swamp Loosestrife is native to wetlands in the eastern half of the United States and Canada. Swamp Loosestrife is also known as Water Willow, False Loosestrife.
Swamp Loosestrife displays a spreading, aquatic perennial growth habit, reaching up to 2 ft tall with a spread of approximately 3 ft. Swamp Loosestrife produces showy pink to purple flowers in clusters.
Leaf size: approximately 4 inches.
How Often Should You Water a Swamp Loosestrife?
Decodon verticillatus requires watering every 2–4 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 2–4 days
Let soil partially dry between waterings
What Light Does the Swamp Loosestrife Need?
Swamp Loosestrife thrives in full sun to part shade.
Light Requirement
Full sun to part shade
What Temperature and Humidity Does the Swamp Loosestrife Prefer?
Decodon verticillatus grows best at temperatures of 60–80°F. Swamp Loosestrife prefers humidity levels of 50–80%. A pebble tray or humidifier helps maintain adequate moisture around the plant.
Temperature
60–80°F
Humidity
50–80%
What Soil Mix Works Best for a Swamp Loosestrife?
Moist, acidic soil with good drainage. Good drainage is essential for Swamp Loosestrife to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Swamp Loosestrife?
Feed Swamp Loosestrife 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 Swamp Loosestrife?
Can be repotted every 2-3 years. 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 Swamp Loosestrife?
Swamp Loosestrife can be propagated through seeds, division of rhizomes.
Is the Swamp Loosestrife Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Swamp Loosestrife, 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 Swamp Loosestrife?
Swamp Loosestrife is susceptible to aphids, caterpillars. 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 Swamp Loosestrife Need?
Swamp Loosestrife grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. Swamp Loosestrife is native to wetlands in the eastern half of the United States and Canada. In cooler regions, grow Swamp Loosestrife as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 13a
Keep exploring plants
Swamp Loosestrife 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 Decodon genus — compare its care with other Decodon species on PlantoScan.
Decodon is part of the Lythraceae plant family — browse all Lythraceae genera and species.
Swamp Loosestrife 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: Decodon verticillatus (L.) Elliott, family Lythraceae (first published in Sketch Bot. S. Carolina [Elliott] 1: 544. 1821) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Swamp Loosestrife, 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 13a, 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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