Control covers for yellow fringed lily are working – next goal is to expand control measures

The first results from the control covers piloted in the Keltalammikki VEX project of the Aura River Foundation are promising. During the summer, covers were installed at sites in Lieto. The covers have prevented light from reaching the yellow fringed lily stands, and nothing has grown underneath them.

Yellow fringed lily needs plenty of light to grow. When a stand is covered, the plant does not receive the light it needs and begins to wither. Trials carried out in Sweden indicate that covering the plant for one growing season may be enough to control it. The Keltalammikki VEX project is now piloting the method for the first time in the Aura River.

First experiences are promising

During the summer, the covers have been monitored regularly, and their effectiveness and the development of the yellow fringed lily stands have been observed. The first experiences show that the method works well.

Small, stunted leaves could occasionally be seen around the edges of the covers. This was expected, as vegetation outside the covers still receives light. Growth was prevented in the area actually covered by the control material.

At this stage, it is not yet known whether the yellow fringed lily has died completely, including its roots, as a result of the covering, or whether only this year’s growth has died. This will only become clear during the next growing season, when the covered sites are monitored to see whether the plant starts growing again.

Expanding control measures is important

Based on observations made this summer, the overall extent of yellow fringed lily stands in the Aura River appears to be roughly the same as last year. However, accurately estimating the area is difficult, so no exact estimates are currently being made of the total amount of covering material that would be needed.

The first results indicate that it would be possible to expand the pilot area. Control measures are particularly important from the uppermost occurrences downstream, in order to prevent the plant from spreading further upstream.

If upstream spread can be prevented, the area where yellow fringed lily occurs will not expand as quickly. At the same time, it is important to remember that the plant can also spread to other waterways.

There are now good conditions for expanding control measures, but expanding the work requires additional funding.

More information is needed about yellow fringed lily

Controlling yellow fringed lily is also made more difficult by the fact that relatively little is still known about the plant’s life cycle in the Finnish environment. For example, there is currently no evidence of yellow fringed lily reproducing from seeds in Finland, and the plant’s full life cycle is not yet known.

More information about the plant’s reproduction could be a valuable help in planning control measures. One interesting research question, for example, is whether all yellow fringed lily individuals in the Aura River originate from the same plant, or whether there is genetic variation in the area that could indicate reproduction through seeds.

The monitoring and spatial data collected in the Keltalammikki VEX project will help improve understanding of the plant’s spread and the effects of control measures. Monitoring will continue during the next growing season, allowing the long-term effects of covering and possible regrowth to be assessed more accurately.

What can you do about yellow fringed lily in autumn?

As yellow fringed lily stands break down in autumn, plant material may be carried by the current and wash up on the banks. Loose plant material that has reached the shore can be collected from the water and dried on the shore. Once dry, it cannot spread to a new waterway.

Yellow fringed lily should not be spread, for example by moving plant material to another location. Cutting or otherwise disturbing the stands should also be avoided, as even small pieces of the plant can spread with the water.

The goal of the Keltalammikki VEX project is to develop an effective and cost-efficient control model for the Aura River that can later also be used in other waterways where yellow fringed lily occurs. The first experiences provide a good starting point for this work.