Callitriche spp.
water starworts
Cosmopolitan - temperate and cooler regions of all inhabited continents
Container Friendly
Native to North America
Overview
Callitriche spp. is a cosmopolitan genus of about 75 small aquatic and semi-aquatic annual and perennial herbs in the family Plantaginaceae, the water starworts. Plants grow as slender, branching stems 2-24 in (5-60 cm) long, fully submerged in water or sprawling over wet mud. The small opposite leaves vary with their setting: submerged leaves are narrow and linear, while stems reaching the surface form floating rosettes of broader, spoon-shaped leaves that look like tiny stars, giving the genus its name. The flowers are minute, green, and without petals, with separate male and female flowers on the same plant, pollinated by water, wind, or self-contact. Small four-lobed fruits follow. Species occupy ponds, slow streams, ditches, springs, and seasonally flooded mud across temperate and cooler regions worldwide, and a few tolerate brackish water. The plants respond quickly to water level, growing submerged forms when flooded and compact land forms on exposed mud. Dense growth can fill small still waters and slow drainage channels.
Native Range
Callitriche spp. occurs nearly worldwide, with native species across North America, Europe, Asia, Africa, Australia, and South America in fresh and occasionally brackish water. Several species are native and widespread in North America. The genus is most common in cool to temperate climates, growing in still or slow-moving water and on wet mud.Suggested Uses
Grown in ponds, water gardens, aquariums, and wildlife pools, where the submerged stems oxygenate the water and shelter small aquatic animals and fish fry. The floating rosettes give cover for insects and amphibians. Used as a submerged oxygenating plant in still and slow water.How to Identify
Appearance
Size & Dimensions
Height2" - 2'
Bloom Information
Callitriche spp. flowers from spring through summer, though the tiny green flowers are easy to overlook. Pollination occurs at or below the water surface, and fruiting follows quickly through the growing season. Flowering has little visual effect, as the plant carries no petals.
Detailed Descriptions
Flower Description
Green, inconspicuousFoliage Description
Light to medium greenGrowing Conditions
Sun Requirements
Requires 4-8 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Callitriche spp. grows in still to slow-moving fresh water and on wet mud in full sun to part shade, rooting in soft silt or organic sediment. It needs permanently moist to flooded conditions and dies back if its water source dries completely, though some species survive as land forms on damp ground. The plants tolerate a wide pH range and cool water, and several are hardy through freezing winters in temperate ponds. Growth can be rapid, and dense mats may need thinning in small ponds and water features. The genus has few pests but can be crowded out by more vigorous aquatic plants.Pruning
Excess growth is raked or netted out of ponds in summer to keep open water. Removed material is left at the pond edge for a day so aquatic life can return to the water. No other pruning is needed.Container Growing
✓ Suitable for container growing
Minimum container size: 1 gallons