What is Blanket weed?

Blanket weed is an algae, it is a relatively primitive form of plant life that is very successful at colonising and dominating an environment under favourable conditions.

Blanket weed spreads and recolonises vegetatively, by branching off and breaking off parts of its own structure which will then colonise new areas.

Biologically speaking, this can be a risky strategy, as if the environmental conditions change, it does not have extensive means of adapting to the changing environment. However, where the environment provides consistent conditions, (as in a koi pond), and the blanket weed is adapted to those conditions, it is a very successful strategy, allowing it to thrive and spread rapidly.

Are there different types of blanket weed. Blanket weed (also referred to as string-algae) is a collective term given to a number of very similar algae that both look and behave identically. The most common genera are:

Cladophora,
Oedogonium and
Spirogyra.

Cladophora means 'branched plant' and when viewed under the microscope, it is possible to see the regular-branding filaments, each of which is divided by cross walls. Absorption of light and nutrients is very efficient in such small structures and so growth can be incredibly rapid. They reproduce both sexually (releasing gametes that unite and develop into new plants), and asexually (releasing small motile spores or simply smaller fragments that break off from the main body).

Blanket weed (Spirogyra adnate) is one of the most prolific aquatic weeds known to amateur and professional pond-keepers in the U.K. In America it is called Long String Algae. This description is pretty accurate because in effect Spirogyra is not a plant but a filamentous algae. There are several other aquatic weeds which are also filamentous algae and the most prevalent of these are Cladophera, Rhizoclonium, Vaucheria and Ulothrix (Ulothrix is a Chlorphyte like Spirogyra and looks very similar)

The cellular structure of a cell, Blanket Weed is a long thin filamentous alga, which like Ulothrix thrives in ornamental ponds. As can be seen from the microscopic observation, the cells of Spirogyra are characterised by helical shaped chloroplasts which give the weed the pronounced green commonly associated with Blanket Weed. Its growth is increased by bright sunlight and shallow fast running water so that it will be found in water-falls and unshaded pond areas. In ornamental ponds which tend be stocked with fish, the tendency to overfeed causes additional fish excrement which contains nutrients favoured by Blanket Weed particularly nitrates and dissolved ammonia. This means that apart from normal growth by photosynthesis the weed will grow even faster.

Spores releasing

The spores of Spirogyra can be preserved in the dry state for many years and come back to life when put into water. Ponds can be free of Blanket Weed for years and suddenly become infested. Pulling weed out actually releases spores produced by conjugation (see photo - bottom left), which then produce even more weed.

The proliferation of Blanket Weed is due to the fact that it grows very quickly in sunlight and if left unchecked can cause serious oxygen depletion in ponds. Additionally it can also cause stress to larger fish that find it an obstruction.

"Definition end: What is Blanket Weed"