Ambrosia is a rather inconspicuous plant. One of many who like to line the roadsides. But where it thrives, the air is enriched with its pollen for weeks. These trigger severe allergies. In many places, the Ambrosia artemisiifolia was therefore declared war. Every specimen discovered should be plucked out, no matter how small it is. But what are the unique identifying features of this dreaded plant?

General information

The ragweed plant is botanically correctly referred to as Ambrosia artemisiifolia. But it is also known under the following names: ragweed, ragweed, ragweed, ragweed, ragweed, wild hemp, ragweed (English name). It is a so-called neophyte because it is not a native plant, but immigrated from America a long time ago. It is keen to reproduce and is conquering ever larger areas in this country.

Possible localities for the Ambrosia

If you want to find and identify the ragweed plant in nature, you should not only familiarize yourself with its identifying features. He should also know possible places where this allergy trigger prefers to settle:

  • Ambrosia plant grows on roadsides
  • along the railway embankments
  • on construction sites and rubble heaps
  • in gravel pits
  • but also in gardens
  • mostly near bird feeders
Tip: During investigations, ragweed seeds were discovered in many bird feed mixtures. That is why you should regularly look for the plant near the feeding places.

Growing season of Ambrosia artemisiifolia

It is also important to know that Ambrosia artemisiifolia
is an annual plant that germinates in spring to summer and dies again in winter. This means that in the spring it is more important to keep an eye out for small ragweed plants and in the autumn there are stately specimens waiting to be discovered.

Note: There is also a perennial species of the Ambrosia plant in this country, the Ambrosia psilostachya or Ambrosia coronopifolia. It is also known as perennial ambrosia.


Depending on the weather, ragweed germinates as early as April. However, other seeds can also germinate by summer. At the beginning it is clear that the ragweed plant is still very small. The size it reaches by summer depends very much on its location and the soil conditions.

  • Growth height can be very different
  • under good conditions it becomes very high
  • can reach a height of 1.8 m
  • under unfavorable conditions it remains small
  • Specimens around 10 cm are quite common
  • the plant branches out profusely
  • still feels airy and light


This allergy trigger has sturdy stems that also branch profusely. They’re all hairy. The basic color is green, but a reddish tinge cannot be overlooked if you look closely. This is stronger the sunnier the plant is. The stem is round and filled.


To identify the plant, the shape of its leaves is an important clue.

  • the coloring is rich green on both sides
  • the leaf veins stand out white to green-white
  • the length is between 5 and 15 cm
  • the leaves have a long stalk
  • they are feathered
  • the lobes are incised to the petiole
  • each lobe is in turn deeply incised several times
  • Leaf shape may vary slightly
  • depending on species, location, stage of development and size
  • when the plant is young, the leaves are opposite
  • approximately up to the sixth pair of leaves
  • later they are placed alternately
  • they don’t smell nice
Tip: The small seedling has two round, stalked cotyledons. Only the pair of leaves that follow has the typical shape that later characterizes the entire plant.


The allergy trigger flowers from July to October. Since the Ambrosia artemisiifolia reproduces exclusively via seeds, it flowers profusely. It is easy to identify based on the flowers. The period from August to September is the main time when the pollen can be expected. Approaching her during this period is not recommended for allergy sufferers. A single ragweed plant is said to produce up to a billion of them. It belongs to the monoecious plants. That is, the same plant forms both male and female flowers. However, in different parts of the plant.

Male flowers and pollen

  • Inflorescences are located at the tips of the stems
  • small single flowers form an upright raceme
  • each 5 to 10 cm long
  • the flowers sit in inverted fruit cups
  • these resemble little bells
  • they are colored green-yellowish
Note: The pollen formed is clearly visible on the flowers. It looks like fine yellow dust.

Female flowers and seeds

  • are formed in smaller numbers
  • they sit in the leaf axils
  • usually below the male flowers
  • usually only one flower per leaf axil, rarely up to seven
  • Flowers are in the shape of a ball
  • they have no stem
  • each female flower contains a fruit
  • this has blunt bumps and is about 3-4 mm in size
  • it contains bell-shaped seeds
  • also the seeds have small protuberances
Note: The ragweed forms seeds that are not able to fly. They simply fall to the ground when ripe. When identifying ragweed in summer or fall, you can look under the plant for this identifying feature. If necessary, you should collect the seeds, because they can still germinate after 40 years.

Risk of confusion with other plants

Many native plant species have pinnate leaves. Not all of them are dangerous for us humans. Many are even useful. Before the plants show their typical flowers, they can easily be mistaken for Ambrosia artemisiifolia at first glance. The following types are often confused with the allergy trigger:

  • field lady’s coat
  • common yarrow
  • Dog chamomile
  • Hundspetersilie
  • vermouth
  • different types of mugwort
  • wild carrot
  • Rock-Leaf Ragwort
  • Jakobskreuzkraut
  • Studentenblume
  • common tansy
  • Eisenkraut
Tip: When identifying the Ambrosia artemisiifolia, use as many characteristics as possible. Picture templates also help to identify the leaves, because the subtle differences are difficult to describe in words. Other types of mugwort also smell more aromatic.

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