Control of the Hercules perennial (giant hogweed)

Herbaceous perennial, also known as giant hogweed, blooms from July to September. Due to its size and large white umbel, it is beautiful to look at, but also poisonous.

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

In order to consistently push back the plant, it is also necessary to combat the stands on private property, as otherwise they could spread again from there. The help of citizens is therefore required and an appeal is made to the owners of affected private properties to take on the removal of the Hercules bushes

Control methods and necessary protective measures

The following measures must be observed when combating Hercules' bush in order to prevent adverse health effects:

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

Herbaceous weed control is a lengthy and labour-intensive process. For this reason, control outside your own garden should be carried out by local authorities in co-operation with experts.

The following control options are available:

• Dig up the plants in April or May when growth is just starting. If the root is cut off at a depth of 15 cm, new shoots are hardly possible. However, success must be monitored.
• During the flowering period from June onwards, the flower spikes must first be cut off before the rest of the plant is removed (beware of plant sap splashes). It is important to avoid dropping the seeds as they will continue to ripen.
• If cones are still hanging on the plant from the previous year, they must be removed with particular care if they still contain seeds. The cones should be burnt on the spot if possible.
• Mowing the plants is suitable for larger contiguous areas. This is best started shortly before flowering. This is when the plant is weakened the most. However, mowing must be repeated approx. 5-6 times at intervals of 10 days, as the Hercules perennial will produce flowers again just 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 a hoe.

Permanent removal of Herculean perennial herbaceous weed also includes multi-year follow-up checks in May/June, as the seeds may still be in the soil and only germinate years later. Dense swards prevent the seeds lying on the ground from germinating.