Hydroponic Pennywort: Growing Hydrocotyle in Shallow Trays
Hydroponic pennywort is water pennywort (Hydrocotyle umbellata) grown in a shallow tray of wet gravel or water. It is a low creeping plant that spreads fast. A tray gives it wet roots and a clear edge.
The short answer
Set rooted runners in a tray of wet gravel with water at or just over the surface. NC State lists full sun to part shade and wet soil. The plant grows 3 to 10 inches tall and spreads 3 to 20 feet. Trim runners at the tray edge.
What is water pennywort?
NC State describes water pennywort as a native perennial with round umbrella shaped leaves 0.5 to 2.5 inches across. It floats or creeps along wet ground and bears small white flowers from late spring to fall. It is hardy in USDA Zones 4 to 10.
Kansas State lists it with the marginal plants that grow with their roots in shallow water.
How do you set up a shallow tray?
NC State lists poorly drained to wet slightly acidic soil and suggests a bog or water garden. Kansas State notes marginal plants can go straight into gravel pockets. Minnesota Extension adds that indoor systems often need winter grow lights.
| Option | What it does | Source |
|---|---|---|
| Gravel tray | Holds runners in wet media | Water Gardening: Plants for the Water Garden (MF2912), K-State Research and Extension |
| Heavy clay loam | Stays in place under water | Water gardens: planting aquatic plants (PlantTalk 1026), Colorado State University Extension |
| Grow light | Adds light in winter indoors | Small scale hydroponics, University of Minnesota Extension |
How do you hold pennywort in bounds?
NC State rates the plant high maintenance for its aggressive habit and notes that water pennywort is a noxious weed or invasive in some areas. Dense mats can change oxygen levels in water too. A rimmed tray gives you a clear trim line.
Regular trimming cuts back the rapid growth. Kansas State adds that division splits a clump into new plants.
How to: step by step
- Buy pennywort from a nursery or aquarium shop.
- Set rooted runners in a tray of gravel.
- Hold water just at or over the gravel.
- Give it full sun to part shade or a grow light.
- Top up the water as it drops.
- Trim runners that reach the tray edge.
Troubleshooting
Runners over the edge: fast growth, so trim back.
Dry gravel: low water, so refill the tray.
Thin growth indoors: low winter light. Add a grow light.
Kind Seed Co shares these plant notes for growers of all kinds. For more on root media see hydroponic in different mediums. Read caring for your hydroponic system for system care. See aquarium water for cannabis and pond water for cannabis for related water notes.
Sources
- Hydrocotyle umbellata (water pennywort), NC State Extension Gardener Plant Toolbox
- Water Gardening: Plants for the Water Garden (MF2912), K-State Research and Extension
- Water gardens: planting aquatic plants (PlantTalk 1026), Colorado State University Extension
- Small scale hydroponics, University of Minnesota Extension
FAQ
Is water pennywort invasive?
NC State notes that it is a noxious weed or invasive in some areas. It spreads 3 to 20 feet and dense mats can change oxygen levels in water.
How big does pennywort get?
NC State lists water pennywort at 3 to 10 inches tall with a spread of 3 to 20 feet.
Does pennywort need fertilizer?
Kansas State University Research and Extension says most marginal plants flourish without supplemental fertilization. It lists pennywort with the marginal plants.
How do you start new pennywort plants?
NC State lists division and seed. Kansas State groups pennywort with plants that are usually propagated by division.
Does pennywort flower?
Yes. NC State notes small white flowers from late spring to fall.
