Zostera japonica
Zostera japonica · Zosteraceae
The gardener's calendar
Ideal time to plant zostera japonica: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Origin
- Pacific Asian coasts (Japan, Korea, China)
- Type
- Submerged aquatic herb
- Foliage
- Evergreen, light to medium green
- Planting depth
- 0.3 to 1.5 m depending on variety
- Growth
- Moderate to fast under optimal conditions
- Hardiness
- Temperate and subtropical coastal zones
- Natural habitat
- Seagrass meadows and brackish waters
Care
Light and exposure
Zostera japonica thrives in clear water with good sunlight, ideally 4 to 6 hours of direct light daily. It tolerates partial shade but grows more slowly. Place it in coastal areas or shallow basins receiving sufficient light for aquatic photosynthesis.
Substrate and soil
This seagrass prefers a sandy or slightly silty substrate, rich in organic matter and well-stabilized. Plant the rhizomes 5-10 cm deep in a marine or coastal substrate. Adding silty sediment promotes rooting and stability.
Water conditions
Japanese eelgrass requires permanent immersion in clear to slightly brackish water, with moderate salinity (2-30 ppt depending on context). Maintain gentle water circulation to prevent localized eutrophication. In closed basins, perform partial water changes regularly to maintain water quality.
Nutrition and feeding
Zostera japonica benefits from nutrient-rich water, but generally requires no supplementary fertilizer in a balanced coastal environment. In nutrient-poor closed basins, very modest nutrient addition (nitrogen, phosphorus) can support growth without promoting harmful algae.
Diseases and pests
This seagrass can be affected by algal epiphytes that reduce light penetration. Maintain good water hygiene and adequate circulation to limit these issues. Excessive sediment degradation or eutrophication promote disease; preserve stable chemical balance.
Did you know?
Zostera japonica is a key species in Asian seagrass meadows, providing food and shelter to thousands of animal species. It is considered an indicator of coastal ecosystem health and is the subject of restoration programs in Japan and Korea to preserve marine biodiversity threatened by coastal urbanization.
Where to buy it
Best planted in spring or autumn, away from frost and heatwaves. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September, October.
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