Watermoss (Salvinia): The Floating Fern That’s More Complex Than It Looks
If you’ve ever spotted what looks like tiny lily pads floating freely on a pond’s surface, you might have encountered watermoss, scientifically known as Salvinia. This isn’t your typical garden plant – it’s actually a fascinating aquatic fern that has stirred up quite a bit of controversy in water gardening circles.
What Exactly Is Watermoss?
Salvinia is a unique floating fern that defies our typical expectations of what ferns should look like. Instead of the feathery fronds we usually associate with ferns, watermoss sports small, oval-shaped leaves that sit prettily on the water’s surface in neat pairs. These aren’t really leaves in the traditional sense – they’re modified fronds that have adapted to life on the water.
As a forb (a non-woody vascular plant), Salvinia can behave as either an annual or perennial depending on your climate and growing conditions. The plant reproduces through spores rather than flowers, which means you won’t see any blooms or attract pollinators with this particular species.
Where You’ll Find Watermoss
Salvinia has established itself across a surprisingly wide range of the United States, currently growing in Alabama, Arizona, Arkansas, California, District of Columbia, Florida, Georgia, Hawaii, Louisiana, Maryland, Massachusetts, Mississippi, New Mexico, New York, North Carolina, Oklahoma, South Carolina, Texas, Virginia, and Puerto Rico. However, it’s important to note that this plant isn’t native to most of these areas.
The plant’s non-native status varies by location. In Hawaii and Puerto Rico, it’s been introduced and now reproduces spontaneously in the wild, persisting without human intervention. Its status in the lower 48 states remains undefined, which should give potential growers pause.
Should You Grow Watermoss in Your Water Garden?
Here’s where things get tricky. While Salvinia can create an attractive floating carpet on ponds and water features, many species within this genus are notorious invasive plants that can quickly take over entire water systems. The problem is that proper identification of specific Salvinia species requires expert knowledge, and some are far more aggressive than others.
Growing Conditions and Care
If you’re in USDA hardiness zones 9-11, Salvinia can potentially survive year-round in outdoor water features. In cooler zones, it typically behaves as an annual, dying back with the first frost.
The plant’s requirements are refreshingly simple:
- Still or very slow-moving freshwater
- Warm temperatures
- High humidity
- No soil required – it’s a true floater
Watermoss grows rapidly under favorable conditions, which can be both a blessing and a curse. While it quickly provides coverage and helps control algae by shading the water, this same rapid growth can lead to overcrowding and oxygen depletion in smaller water features.
A Word of Caution
Given the uncertain invasive status and the genus’s reputation for aggressive spreading, we’d recommend extreme caution before introducing any Salvinia species to your water garden. If you’re looking for attractive aquatic plants, consider exploring native alternatives like American lotus, water lilies native to your region, or native floating heart species.
If you already have watermoss in your water feature, monitor its growth carefully and be prepared to thin it regularly to prevent it from overwhelming your aquatic ecosystem. Never dispose of excess plant material in natural water bodies – always compost or dispose of it properly on land.
The Bottom Line
While Salvinia can be an interesting addition to contained water features, its potential for invasive behavior makes it a plant that requires careful consideration and responsible management. When in doubt, choosing native aquatic plants will always be the safer bet for both your garden and the local ecosystem.
