Are aquatic weeds more of a problem in summer?

13.6.24

Do aquatic weeds pose more of a problem in commercial waterways, lakes and domestic ponds during summer? As a general rule of thumb, all shapes and sizes of ponds and lakes can, unfortunately, get choked with weeds when it's hotter.

Aquatic weeds and warmer temperatures

It’s common for weeds and algae to tip over into nuisance territory in mid-to-late-summer when water temperatures climb to 6°C (43°F). Many plants enjoy a burst of growth in warmer temperatures of course, and aquatic weeds can quickly take over lakes, waterways and garden ponds. And when weeds reach roughly a 20% surface-coverage of the water or start propagating rapidly, then it’s potentially very problematic.

Longer daylight hours fuel the growth of aquatic weeds, thanks to a flood of phosphorous and nitrogen, and before you know it you have an aquatic weed invasion on your hands. Especially when you factor in nutrient-rich run-off from agricultural land.

The environmental impact

With water weeds exploding in summer, there's also an environmental impact. It’s crucial to catch them early if you want to control them and avoid a situation that could potentially lay waste to other water-borne species and clog up natural waterways.

types of aquatic weed

Among the worst offenders in UK waters are Water Fern, Floating Pennywort, and Parrot’s Feather.

Water fern (Azolla Filiculoides)

Azolla loves ponds, lakes, canals, ditches and lazy rivers. The density of this floating aquatic plant can block out the sun if left untreated, which is bad news for other vegetation and wildlife.

Floating pennywort (Hydrocotyle Ranunculoides)

The perennial aquatic plant Floating Pennywort is native to North America but has now found its way into the UK. It favours more stagnant bodies of water like ponds and canals. It can cause issues for fish and other aquatic species because this water weed restricts their room to move.

Parrot’s feather (Myriophyllum Aquaticum)

This one sounds nice and fluffy but don't be fooled. A submerged aquatic plant native to South America but now also found in the UK, Parrot’s Feather is a highly invasive and potentially choking rival for native vegetation that blocks out the sun.

Other factors that contribute to aquatic weed growth in summer

Lack of scrutiny

Regardless of the body of water, we recommend ongoing maintenance and this is something you can always talk to us about.

More people using the water

Greater footfall around riverbanks and such in summer can cause the release into the water of eroded sediment and with it nutrients on which algae and weeds feed. Likewise the dropping of litter. Water recreational activities can also propagate weeds into new ecosystems.

Repairing erosion damage along the shoreline and perhaps planting as a means of a natural defence buffer are two ways to help keep weed numbers down in summer.

Algae in domestic ponds

Most ponds will develop algae and blanket weeds, especially in sunny conditions. Algae form when the water is too nutrient-rich, and this could also be down to invasive pond weeds, likewise other pond debris.