Control of the giant hogweed (Herkulesstaude)

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

The perennial with the white umbels has been spreading rapidly for several decades. It finds good conditions on fallow land and banks. One plant reproduces with up to 50,000 seeds that can germinate for up to 10 years. The light and buoyant seeds spread along waterways, roads and railway tracks.

In order to push the plant back consistently, it is also necessary to combat the stands on private property, as otherwise they can spread again from there. The help of the citizens is therefore needed and it is appealed to the owners of the affected private properties to take care of the removal of the Hercules perennials.

Control methods and necessary protective measures

The following measures must be observed when controlling Hercules perennialis in order to prevent adverse health effects:

• Protective clothing is essential (long trousers, thick jumper, goggles, face shield and especially gloves).
• If possible, remove plants at dusk or when it is very cloudy.
• Face and hands should be additionally protected with a sun cream with a high sun protection factor.

The control of Hercules Perennialis is lengthy and labour-intensive. Therefore, control outside one's own garden should be carried out at community level together with experts.

The following control options are available:

• Dig up the plants in April or May when growth is just beginning. If the root is cut off at a soil depth of 15 cm, new sprouting is hardly possible. However, a success control is necessary.
• During the flowering period from June onwards, the flower umbels must first be chopped off before the rest of the plant is removed (beware of plant sap splashes). The seeds must be prevented from falling off, as they will ripen.
• If there are still umbels hanging on the plant from the previous year, these must be removed with particular care if they still contain seeds. If possible, the fruit umbels should be burnt on the spot.
• On larger contiguous areas, mowing the plants is suitable. It is best to start shortly before flowering. This is the time when the plant is weakened the most. However, once started, mowing must be repeated approx. 5-6 times at intervals of 10 days, as the Hercules perennial produces flowers again only 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.

Permanent removal of Hercules perennialis also includes multi-annual follow-up inspections in May/June because the seed can still be in the soil and only germinate years later. Dense swards prevent the seeds lying on the ground from germinating.