Southern Water Fern Plant Care
Blechnum australe L.
Updated · Sources · How we source care data
Every 7–10 days
Bright indirect to low light
60–75°F
50–70%
At a glance
How do you care for Southern Water Fern?
Water Southern Water Fern every 7–10 days, letting the top layer of soil dry out between waterings, and give it bright indirect to low light. It prefers temperatures of 60–75°F (16–24°C) and 50–70% humidity. Fertilize it every 6 months during the growing season.
What Is the Southern Water Fern?
Southern Water Fern (Blechnum australe) belongs to the Blechnaceae family within the Blechnum genus.
Southern Water Fern displays a low rosette, spreading growth habit, reaching up to 1.5 ft tall with a spread of approximately 2 ft. Southern Water Fern produces non-flowering.
Leaf size: approximately 12 inches.
How Often Should You Water a Southern Water Fern?
Blechnum australe requires watering every 7–10 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 7–10 days
Let soil partially dry between waterings
What Light Does the Southern Water Fern Need?
Southern Water Fern thrives in bright indirect to low light. Avoid placing Southern Water Fern in direct, harsh sunlight for extended periods, as this can scorch the foliage.
Light Requirement
Bright indirect to low light
What Temperature and Humidity Does the Southern Water Fern Prefer?
Blechnum australe grows best at temperatures of 60–75°F. Southern Water Fern prefers humidity levels of 50–70%. A pebble tray or humidifier helps maintain adequate moisture around the plant.
Temperature
60–75°F
Humidity
50–70%
What Soil Mix Works Best for a Southern Water Fern?
Rich, well-draining soil with high organic content. Good drainage is essential for Southern Water Fern to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Southern Water Fern?
Feed Southern Water Fern 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 Southern Water Fern?
Repot every 2-3 years in 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 Southern Water Fern?
Southern Water Fern can be propagated through spores, division of rhizomes. Similar propagation techniques also apply to blechnum castaneum plant care, which shares the same genus.
Is the Southern Water Fern Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Southern Water Fern, 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 Southern Water Fern?
Southern Water Fern is susceptible to mealybugs, scale insects. 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 Southern Water Fern Need?
Southern Water Fern grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. In cooler regions, grow Southern Water Fern as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 13a
Keep exploring plants
Southern Water Fern 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 Blechnum genus — compare its care with other Blechnum species on PlantoScan.
Blechnum is part of the Blechnaceae plant family — browse all Blechnaceae genera and species.
Southern Water Fern copes with lower light than most plants — browse the full list of low-light plants.
More Blechnum Species
Other Blechnum species in PlantoScan's care catalogue share similar watering, light, and soil preferences:
Sources
- Scientific name & taxonomy: Blechnum australe L., family Blechnaceae (first published in Mant. Pl. 130. 1767 [15-31 Oct 1767]) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Southern Water Fern, 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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