Understanding Blanket Weed: A Comprehensive Guide
What is Blanket Weed?
Blanket weed is a type of algae that commonly grows in garden ponds, especially during spring and early summer. It forms cotton-like clumps of fine, hair-like, bright green strands in the water. Blanket weed thrives when there are high levels of nutrients in the water, such as from fertilizers, fish waste, or organic debris.
Is Blanket Weed Harmful?
Small amounts of blanket weed are not usually a problem, especially early in the year. However, excessive blanket weed can inhibit plant growth and reduce oxygen levels in the water, which can affect fish health. It can also make the pond look unsightly. On the other hand, blanket weed provides shelter and food for wildlife such as newts, toads, and tadpoles.
Causes of Blanket Weed Growth
Blanket weed thrives in water that is rich in nutrients. Common sources of nutrients include:
- Tap water
- Fertilizers and manures
- Fish waste and surplus food
- Organic debris (e.g., leaves, plant matter)
Preventing Blanket Weed
To prevent blanket weed growth, you can take the following steps:
- Use rainwater instead of tap water to fill or top up the pond.
- Avoid using fertilizers and manures near the pond.
- Keep the fish population in the pond to a minimum and avoid overfeeding.
- Regularly remove leaves and other organic matter from the pond.
- Use aquatic planting soil or sieved topsoil for pond plants.
- Grow a variety of plants in the pond to shade the water and absorb nutrients.
Using Plants to Control Blanket Weed
Creating a natural balance of plants in the pond can help reduce and prevent blanket weed growth. Aquatic and marginal plants shade the water’s surface, limiting sunlight exposure and inhibiting blanket weed growth. The roots of these plants also absorb nutrients from the pond, effectively “starving out” the algae. Aim to cover at least a third of the pond’s surface with floating foliage or submerged oxygenating plants.
Treating Blanket Weed in Ponds
Various products are available to treat blanket weed, but it’s important to note that most only tackle the symptoms rather than the underlying cause. Natural and environmentally friendly products are the safest choice for wildlife and fish. Some effective treatments include:
- Barley straw: Releases chemicals that inhibit algae growth.
- Pond Balance: Reduces nutrients and alters water chemistry.
- Pond Clean: Reduces nitrogen and ammonia levels.
- Pond Clear: Reduces nutrient levels and speeds up organic debris digestion.
- Pond dye: Blocks sunlight, inhibiting algal growth.
Should I Remove Blanket Weed?
During spring, it’s best to leave blanket weed undisturbed to provide food and shelter for wildlife. Later in the season, if blanket weed is still present in large quantities, you can remove it using a cane, net, or plastic-tined rake. Pile the weed by the side of the pond for a few days to allow creatures to return to the water.
Conclusion
Blanket weed is a common issue in garden ponds, but it can be effectively controlled through a combination of prevention and treatment methods. By understanding the causes of blanket weed growth and implementing the appropriate measures, you can maintain a healthy and balanced pond ecosystem.
