Ragwort, Senecio jacobaea – Recognize and combat

Due to errors in the planting and management of green spaces, there has been an undesirable and unnatural spread of ragweed, as it is also called, in recent years. Any gap that opened up, such as on fallow fields, farmland, along railroad embankments and roadside embankments, the plant used to settle. This development can be observed above all in Schleswig-Holstein and North Rhine-Westphalia. This is how she found her way into many a hobby garden. The biennial ragwort can be recognized by the following characteristics:

• In the first year, only a green leaf rosette forms.
• The basal leaves are about 20 cm long.
• In the second year, the yellow-colored flower umbels appear.
• 15 to 20 yellow flower heads up to 25 mm in diameter.
• Long ray florets are arranged around the flower heads.
• Overall, the flower is reminiscent of a yellow daisy.
• 13 green bracts with black tips = important identification feature.
• Possibly, but not always, 2 green, tightly fitting outer bracts.
• Growth height of the stems 30 cm to 100 cm.
• Characteristics of the stems: reddish base turning greenish upwards.
• Stems are sometimes hairy like a cobweb and always have angular grooves.
• Green leaves are pinnate and stand out at right angles.
• Leaves of the rosettes are not yet pinnate, but rounded.
• Root system: taproot with numerous fibrous roots up to 30 cm long.
• Flowering period: June to October.

The main flowering time is around June 25th, the day of St. James, from which the name is derived. Since a plant can have up to 100,000 flying seeds, this fact alone explains the alarming spread of Senecio jacobaea. The seeds can fly up to 50 m with the help of the wind. They can then germinate on and in the ground for up to 25 years; a ticking weed bomb in the bed for every hobby gardener.

Distinguishing feature: scaly caterpillars

Since Senecio jacobaea can easily be confused with other flowering plants such as the useful St. John’s wort, another unmistakable identifier of the poisonous herb should be mentioned at this point. The calicoa bear is a butterfly that has specialized on the plant. The diurnal moth is easy to recognize because it is black with two red dots on each of its wings and two long red stripes on the edge of the wings. Plants on which this insect settles areundoubtedly Jacob’s cruciferous herbs. Its larvae feed exclusively on this plant and are also easy to spot because they are conspicuously ringed in yellow and black. However, they are unsuitable for biological control, because they only nibble at the plant and then pupate in the ground, while the ragweed recovers from the attack in peace and quiet.

poison content

All parts of the ragwort contain a liver-damaging toxin, which inevitably leads to death above a certain level. The poison content in the flowers is usually at least twice as high as in the herb. The fact that Ragwort that gets into the hay or silage retains its effectiveness there, which is not the case with most other poisonous herbs, is particularly fatal for cattle and horse owners. This can also lead to gradual poisoning. Researchers have identified the following lethal doses:

• Horses: 40 to 80 g per kg body weight
• Cattle: 140 g per kg body weight
• Sheep and goats: 2 kg per kg of body weight

Rabbits and other small rodents do not show any negative reactions after eating the herb. Nevertheless, this should be a warning signal for garden lovers who also keep their own rabbit farm. With the meat of the animals, the poison in their organism is absorbed by humans when they eat it. Adding to the danger is the knowledge that this toxin is not eliminated from the body and therefore accumulates over time. The control programs of the Federal Institute for Risk Assessment with regard to the amount of poisonous ragwort contained in food have only just begun. Since ragwort is also popular with bees as a source of pollen, toxic components have already been detected in honey.

Fight

If the Ragwort is not disturbed in its growth, it develops as a biennial plant that dies after flowering and seed formation. Once they have established themselves in an area, there is no use mowing them down again and again, because in this case their vitality is strengthened rather than fought. Then she survives for more than two years. Simply mowing this penetrating plant again and again has the opposite effect. It is much more effective to counter the spread as early as possible with the help of preventive measures:

• Avoid planting gaps in the garden.
• Seeds prefer open ground to settle.
• Any gaps, e.g. B. in the lawn, plant again immediately.
• Prefer competitive grasses, such as crested grass or ryegrass.
• Cut out the rosettes of the first year.
• Pull out the roots of flowering ragweed.
• A weed puller saves tedious bending over and catches all the roots.
• Remove after a rain shower when the ground is soft.
• Re-examine infested areas every 4 days.
• Be sure to wear gloves and eye protection.
• Do not dispose of in the compost.

When combating it, it is essential that all parts of the root are removed, because the ragweed will even sprout from the smallest pieces of root.

Tips for effectively removing individual plants

If you don’t want to buy one of the rather expensive weeders, you can use the digging fork to remove individual Jacob’s cruciferous herbs. Because it is so important to capture the entire plant, including all roots, the following handling tips will help ensure the job is done successfully.

With the rosettes, the digging fork is pushed into the ground at a maximum angle of 45° and lifted slightly. This process robs the plant of its footing and it can be easily pulled out by hand. Experienced gardeners reach under the rosette or the mature plant and, with a little finesse, lift it completely out of the ground. If the ground is particularly hard because it hasn’t rained for a long time, a second stitch is made at right angles to the first. Under no circumstances should you dig into the ground at a 180° angle, as this will have the effect of cutting a spade and will destroy the turf (if it is still there).

Chemical control only by experts

If the mechanical means of control are unsuccessful and ragwort spreads unstoppably in the garden, on the lawn and on embankments, the only option is to use chemical means. Biological approaches are either still in the development phase or have not proven effective. In Germany, the use of herbicides is reserved exclusively for tested and certified professionals. They can examine whether a large-scale application is necessary or whether a single stick treatment with the help of a wick spreader is sufficient.

• The ideal time is when the plant is 15 to 20 cm tall.
• Chemical control can only be done to a limited extent.
• Please note the waiting time after the treatment.
• Remove and burn all treated plants.
• Further treatment may be necessary.

The advantage of the single treatment lies in particular in the minimal dosage of the herbicide that is applied to the plant through the filling tube. A light dab of 2 to 4 leaves is enough. If some food coloring is added to the agent, it is easy to see which weeds have already been treated.

Related species that are also poisonous

Ragwort has a few close relatives that look very similar to it and are also poisonous, although not always to the same degree:

Spring Ragwort

• Flowering from April to May
• Growth height up to a maximum of 50 cm
• Stems also reddish in color
• yellow flowers
• Petals shorter and more rounded

fox ragwort

• Growth height up to 140 cm
• liver-damaging and carcinogenic
• yellow, very thin ray florets
• lanceolate leaves
• Flowering period June to September

Alpine Ragwort – Alpine Ragwort

• Growth height up to 100 cm
• golden flowers
• panicle-like inflorescence
• only occurs in the Alps
• toxic to grazing livestock

Raukenblättriges Geiskraut – Senecio erucifolius

• yellow flowering daisy family
• very similar to ragwort
• often occurs together
• then flowers 6 to 8 weeks later

Water Ragwort – Water Ragwort

• Growth height 40 cm to 80 cm
• Flowering period June to October
• small, yellow flowers at the tips
• the upright growth of the stems is striking
• significantly less poisonous than Ragwort

Common Bloodweed – Senecio vulgaris

• Growth height 10 cm to 30 cm
• yellow flower heads
• inconspicuous yellow tubular flowers
• Flowering time February to November
• only slightly toxic

Conclusion
Actually, ragwort is one of the long-established, native wild herbs and it has received little attention. In recent years, however, the herb, which has the botanical name Senecio jacobaea, has been spreading at an alarming rate because all parts of it are highly toxic and cause liver damage that can lead to death. Horses in particular are sensitive to the herb; but cattle, sheep and goats also suffer. In this way, there is a risk that the poison will also get into the human organism via food. Control is therefore essential – even in your own, manageable ornamental and kitchen garden.