Bekämpfung der Herkulesstaude (Riesenbärenklau)

From July to September, the herbaceous plant, also known as giant hogweed, blooms.  Because of its size and the large white umbel, it is beautiful to look at, but also poisonous.

For several decades, the perennial with the white umbelflowers has been spreading rapidly. It finds good conditions on fallow land and on riparian strips. A plant reproduces with up to 50,000 seeds, which are germinable for up to 10 years. The light and buoyant seeds spread along waters, roads and tracks.

In order to consistently push back the plant, it is also necessary to combat the stocks on private land, otherwise they can spread from there again. It is therefore necessary for the help of the citizens and it is appealed to the owners of affected private properties to take care of the removal of the Hercules plants.

Control methods and necessary protective measures

The following measures must be observed in the control of the herbaceous shrub in order to prevent health impairments: 

• Protective clothing is essential (long trousers, thick sweater, goggles, face protection and especially gloves).
• If possible, remove plants at dusk or in heavy clouds.
• Face and hands should also be protected with a sunscreen with a high sun protection factor .

The control of the herbaceous shrub is lengthy and labor-intensive. Therefore, you should carry out the control outside your own garden at community level together with experts.

The following control options are available:

• Digging up the plants in April or May, when growth is just beginning. If the root is tapped at a depth of 15 cm, a new shoot is hardly possible. However, a success control is necessary.
• During the flowering period from June, the umbels must first be chopped off before the rest of the plant is removed (beware of plant sap splashes). Falling off of the seeds must be avoided because they ripen.
• If umbels are still hanging on the plant from the previous year, they must be removed particularly carefully if they still contain seeds. The fruit umbels should be burned on the spot if possible . 
• On larger contiguous areas, the mowing of the plants is suitable. This is best started shortly before flowering. At this time, the plant is weakened the most. However, once started, the mowing must be repeated about 5-6 times at intervals of 10 days, as the Hercules plant forms flowers again 14 days after mowing, sometimes at a height of less than 10 cm. Only this frequent repetition promises success.
• Individual new seedlings can be removed with the hoe .

A permanent removal of the Hercules shrub also includes several years of follow-up checks in May/June because the seed can still be in the soil and germinate years later. Dense turf prevents the seeds lying on the ground from germinating. 

 

All plant parts of the herbaceous plant contain a dangerous substance, furocoumarin, which gets on the skin upon contact with the plant sap. When exposed to sunlight , furocoumarin together with the body's own protein forms an antigen that leads to a strong allergic reaction .

Blisters form on the skin, reminiscent of a severe burn and discoloration that can last for months. Vapors can also affect health and cause nausea, for example. Even dried stems and flowers as well as the seeds still contain the dangerous furocoumarin. It is treacherous that immediately after contact no visible reaction is recognizable . The greatest danger from sunlight is half an hour to 2 hours after skin contact.

How to behave in case of contact with the Hercules shrub?

If you have touched the Hercules plant or if you suspect that you have done so, you should immediately avoid the sun. The affected areas should be thoroughly washed with soap and water , even if no reaction is yet visible. It makes sense to apply a sunscreen afterwards . Also in the next 2 - 3 days the sun is to be avoided.

Mapping the occurrence of Hercules is important for permanent removal. As a result, even years later, after the removal of the plant, it is still known in which places new plants may be able to grow due to seeds present in the  soil.

To help with containment, report the locations of the plants to the municipality, your green space office, the nature conservation authority or the forestry office.