Overview
Ulva lactuca is a green marine alga forming thin, flat sheets of bright translucent green that grow attached to rock and other surfaces in the sea. The blade is two cell layers thick, 4-12 inches (10-30 cm) across and sometimes larger, with ruffled, wavy margins and an irregular, often lobed or torn outline. It attaches by a small disc-like holdfast at the base but has no true roots, stems, or leaves, taking up nutrients directly from the surrounding seawater across its whole surface. The sheet is soft and slippery and tears readily in strong surf. Reproduction alternates between similar-looking sexual and asexual generations, releasing swimming spores and gametes into the water rather than producing flowers or seeds. It grows fastest in nutrient-rich, sheltered water and can form large floating mats where nutrient levels are high. Detached sheets wash up on shores and break down. It lives between the mid-tide level and the shallow subtidal zone on rocky coasts worldwide.
Native Range
Found on rocky shores and in shallow coastal waters worldwide, from temperate to tropical seas, including the coasts of Europe, the Americas, Asia, Australia, and Africa. Grows from the middle shore into the shallow subtidal zone, and grows densely in nutrient-rich, sheltered bays and estuaries.Suggested Uses
Grown in marine aquariums and refugiums to take up excess nutrients and to feed grazing fish and invertebrates. Harvested from the wild and farmed as an edible seaweed, eaten fresh in salads, dried, or in soups. It is also gathered as a soil conditioner and fertiliser. It is not suited to fresh water or terrestrial growing.How to Identify
Appearance
Colors
Foliage Colors
Bloom Information
This alga does not flower. It reproduces by releasing swimming spores and gametes into the seawater, alternating between sexual and asexual generations that look alike. Growth and reproduction are fastest in the warmer, brighter months and in nutrient-rich water. Large blooms can build up in summer where coastal nutrient levels are high.
Detailed Descriptions
Foliage Description
bright greenGrowing Conditions
Water & Climate
Water Needs
Care & Maintenance
Care Guide
Grows submerged or in the intertidal zone on rocky coasts and in marine aquariums, attached to rock or hard surfaces in moving, oxygenated seawater. It needs full-strength or near-full-strength seawater, light, and dissolved nutrients, and will not grow in fresh water or in soil. In aquariums it is grown in refugiums with steady water flow and lighting to take up excess nutrients. It grows quickly when nutrients are plentiful and can overgrow other surfaces. It bleaches and breaks down in stagnant, warm, low-oxygen water. Detached pieces keep growing while they stay wet and lit.Pruning
No pruning is required. In aquariums, surplus growth is harvested by hand to control its spread and to remove absorbed nutrients. Loose or decaying pieces are taken out to keep the water clear.Container Growing
✓ Suitable for container growing