Freitag, 30. August 2013

Field Trip to Duisburg-Homberg (August 25th, 2013)

Last Week, I participated in a Field Trip to Homberg in Duisburg, Western Germany. This Field Trip was organized by the Botanischer Verein Bochum e. V., which I belong. The trip went to the floodplains of the Rhine in this area. We looked for some interesting species, which are common at the shore of the Lower Rhine.

1) Areal

Homberg is a former village, which is located at the western shore of the River Rhine in North-Rhine Westphalia, Western Germany. In 1975 it became part of the larger City of Duisburg on the eastern shore of the Rhine. However, with the large river as a kind of barrier, Homberg (and other urban districts like Hochheide and Baerl) remain mostly independent from the rest of Duisburg. For many people, Homberg is more part of the Lower Rhine plains than of the Ruhr Area like the Rest of Duisburg.

Duisburg-Homberg: floodplains (pasture)

The actual area of the Field Trip were a small part of the floodplains in this region. Located directly at the Shore of the Rhine, the areal is exposed to frequently flooding. Plants, which grow here, have to deal with this circumstance and its side-effects like permanent wetness, mechanical stress due to flow or wind and a high entry of nutrients by the water.

Small group of trees with Silver Willows

Large Trees are missing completely. The Silver willow (Salix alba) and sometimes the black alder (Alnus glutinosa) are the largest and most common trees in this region.

In summary, the areal can be divided in three parts

  1. The Pasture: This is a large meadow between the dyke and the river. It's used as a pasture and also as a kind of basin for the water, when it occurs on the shore. In this area, you can find many different species, which are typical for wet meadows and extensively used pastures like Lamium album or Heracleum sphondylium.
  1. Gravel pit: The bottom of Rhine contains much gravel, which is used by industry as building material. The gravel is dug out by excavators. This creates large pits and a kind of ruderal wastelands with a denser soil. When flooded, the soil became muddy. Such places are settled by pioneers like Datura stromonium, Pulicaria vulgaris or Polygonum ficifolius.
gravel pit
  1. Sandbar & Gravel banks: Last but not least, the Field Trip leads to the shore of the Rhine. Here, we found two different types of soil: sand and gravel. In contrast to the gravel pit, the soil isn't dense and not so muddy (but some muddy places with silt are also possible). Anyway, this soils are also rather the home of pioneers like Stachys palustris, Bolbochoenus maritimus, Potentilla anserina or Cynodon dactylon.


    gravel shore
Curiously, you can also find some exotic species in this area, which are definetly not native to Germany. Their seeds were stranded by the river and sometimes, they begin to grow. Such species are different sorts of tomatoes (Solanum lycopersicum), melons (Cucumis agg.) or even rice (Oryza sativa). A large River like the Rhine is just a kind of dump and the seeds of such plants can enter the river by waste water or food waste.

another view on the gravel pit

Unfortunately, the areal was flooded for a long time and as a result, many plants aren't flowering. However, we still found many different species in the floodplains, as you can see on the following pictures.

2) Species

The following list contains the most important, interesting or typical plants, which were found in the area. Green are plants from the pasture, brown are plants from the gravel pit and yellow are plants from the sanbank and the gravel bank.

3) Pictures

3.1 Pasture

 Brassica nigra

 Eryngium campestre

Lamium album

Lysimachia vulgaris

 Lepidium latifolium

Sapponaria officinalis

Cichorium intybus
3.2 Gravel Pit

 Amaranthus albus 

 Amaranthus powelii

Chenopodium ficilifolius

 Chenopodium glaucum

Datura stramonium

 Euphorbia esula

 Medicago falcata

Pulicaria vulgaris

3.3 Sandbank & Gravel Bank

 Bolboschoenus maritiumus

Corispermum leptopterum

Cynodon dactylon

 Juncus compressus

 Potentilla anserina

 Salix alba

Butomus umbellatus

 Solanum lycopersicum

Donnerstag, 22. August 2013

Plant of the Day (August 22nd, 2013) - Listera ovata (L.) R. Br. (also: Neottia ovata (L.) Bluff. & Fingerh.)

In today's portrait, I want to show you Listera ovata (L.) R. Br.; an orchid from the Orchidaceae family (sub-species: Orchideoideae). The Orchidaceae are a form-rich family within the Asperagaless; an order of the monocotyledons. The common German name of this orchid is “Großes Zweiblatt”, while the common English name is “Common Twayblade”.

L. ovata - habitus

Please note: recent, phylogenetic researches have found out a close relation between this species and Neottia nidus-avis (L.) Rich. (“Bird's nest orchid”). As a result, the species is also known as Neottia ovata in newer literature. However, I will use the old name, because it's still more common in books.

1) Description

L. ovata is a perennial plant, which can reach an average height between 20 and 70 centimeters (7.9 to 27.5 inches). It has a short, barrel-like rhizome and flat, creeping roots. The stalk is covered with a loose fluff. The plant also lives in a symbiosis with a fungus, which grows around the roots. This form of symbiosis (Ecto-Mycorrhiza) is very common at the orchids.

L. ovata - the two, egg-shaped leaves

The plant is nearly leafless and has only two large, dark-green leaves at its base, which are egg-shaped. They are arranged in a nearly decussate leaf-pattern. As with the most monocotyledons, the leaf-veins are running parallel to each other. The two-leaves are also responsible for the German name “Zweiblatt”, what means “two-leafed (herb)”). In some cases, there are also some dark spots on the leaves.

L. ovata - flowers

The inflorescence is a single raceme with 20 to 40 flowers. Unlike tropical orchids, the flowers aren't very spectacular. They are small and have a yellowish-green color. As with the most orchids, the flowers have a very unique morphology and consist of two circles: outer and inner tepals. One of the inner tepals is much longer than the rest and is called labellum (lip). The labellum of L. ovata is deeply divided into two tips.

 L. ovata - flowers

In addition, one of the outer petals is puffed-up and form a helm like structure, which closes the flower a little bit. As a result, a potential pollinator (mostly scorpion wasps and beetles), must land on the labellum and crawl into the flower. Now, L. ovata can attach a small package of pollen at the back of the insect.

 L. ovata -  leaves & stalk

The ripe fruits are small capsules with many seeds per capsule. Flowering time is between May and June. However, vegetative reproduction is also possible.

2) Distribution

L. ovata is native to Europe but can also be found in some regions of North America as Neophyte. It grows in deciduous forests, riparian forests, bogs and on meadows. It prefers fresh, shady places on lime or loam, which are rich of nutrients.

young, deciduous forests on lime, like this one in Grube Haan,
are a typical habitats of L. ovata

Like all orchids, the species is strictly protected by the “Convention on International Trade in Endangered Species of Wild Fauna and Flora“ (CITES). So, the destruction and poaching of this plant is forbidden.

Sonntag, 11. August 2013

Addition to Daucus carota ssp. carota L.

Here is a little Addition to my last post about D. carota. On this picture, you can see the nest-like habitus of the inflorescence after flowering. You can also see the Achenes with their spikes.

D. carota  - folded inflorescence with fruits (achenes)

Freitag, 9. August 2013

Plant of the Day (August 9th, 2013) - Daucus carota ssp. carota L.

Like H. sphondylium, today's “Plant of the Day” is also a member of the Apiaceae family. This species is Daucus carota L.; known as “Wilde Möhre” in Germany and as “Wild Carrot” or “bishop's lace” in English. However, there are also some important sub-species of D. carota

  • Daucus carota ssp carota: Wild carrot
  • Daucus carota ssp. sativa: Cultured carrot (the vegetable)
  • Daucus carota ssp maximus: Giant carrot
  • Daucus carota ssp carota: Black carrot

This article is about D. carota ssp. Carota. For simplicity, I will call it D. carota.

1) Description

D. carota is a biennial plant, which can reach heights between 20 and 100 centimeters (8.0 to 39.5 inches). Its a deep-rooting plant, which is anchored in the ground by a long main-root. Together with the hypocotyl (the part of the shoot between the root and the first leaves), the root forms a thick and long bulb: the carrot.

D. carota - habitus

In contrast to the cultured carrot; the bulb of D. carota isn't orange, because the concentration of Carotene is much lower than in the cultured sub-species. In nature, the bulb acts as a reservoir for nutrients.

 D. carota - leaf

The grey-green leaves are double or triple pinnate, while the stalk is covered with some bristles. The bracts of the Invulucrum are also pinnate but very narrow. As a result, the bracts look a little bit fibrous or frayed. 

  D. carota - stalk with bristles

As an Apiaceae, the inflorescence of D. carota is a umbel, which consists of many smaller sub-umbels (between 15 and 50 per umbel). In contrast to other plants from the Apiaceae (like H. sphondylium), the inflorescence is nearly flat and only slightly curved.

 D. carota - invulucrum
Each of the smaller umbels consists of small flowers with white petals. However, one flower of the central umbel (in the center of the whole inflorescence) is deep purple to nearly black. This is a distinctive feature of the species and makes it easy to distinguish D. carota from other Apiaceae (but be careful: in some rare cases, the black central flower is missing).

  D. carota - inflorescence with black flower in the center
(red circle). It works, because a fly is on the flowers
 (green circle)

With this black flower, the plant simulates the presence of an insect, because the flower looks a little bit like a fly. Thereby, other insects (potential pollinators) are attracted, because they prefer plants, which are already visited by other insects. Flowering time is between June and September.

 D. carota - the unique, black flower in the center

After successful pollination, the whole umbel contracts and forms a distinctive, nest-like structure, which unfolds when becoming wet. The ripe fruits are Achenes (double fruits), with four rows of spikes per single fruit (totally eight).

2) Distribution

D. carota is native to the temperate regions of Eurasia and North Africa but can also be found in other parts of the world as Neophyte. It's very common in the lowlands and prefers fresh, nutrient-rich places to grow. As a synanthropic, it benefits from anthropogenic influence and can be found on pastures, meadows but also on ruderal wastelands and along creeks and ditches.

 D. carota - habitus

The species is one primogenitor of the cultivated Carrot, which is the result of a cross-breeding between D. carota ssp. carota and the Black Carrot (Daucus carota ssp. afghanicus), which is native to the orient.

Freitag, 2. August 2013

Plant of the Day (August 1st, 2013) - Heracleum sphondylium L.

Today's „Plant of the Day“ is Heracleum sphondylium L. from the Apiacae (aka Umbeliferacae) family. In German, the species is known as “Wiesenbärenklau” and in English as “Common Hogweed”. The plant is the “smaller brother” of Heracleum mantegazzianum Sommier & Levier; the notorious “Giant Hogweed” (Riesenbärenklau).

 H. sphondylium - habitus

1) Description

H. sphondylium is a larger, perennial plant, which can reach heights between 50 and 150 centimeters (19.5 to 59 inches). The stalk is furrowed and covered with bristles. Its also hollow. The leaves are arranged in a semi-rosette. In contrast to a real rosette, leaves are also along the stalk but concentrated in the lower regions.

H. sphondylium - leaf-sheath and stalk

The leaves are irregularly pinnate to lobed. Their margin is roughly serrated. Another distinctive feature of this plant is the puffed-up leaf-sheath at the base of each leaf. The bracts of the umbels, the invulucrum, are very narrow and nearly filamentous. 

H. sphondylium - pinnate leaf of a young plant

As with all Apiaceae, the inflorescences of H. sphondylium are umbels. Specifically, these umbels are double umbels, which consist of two smaller umbels. Each umbel consists again of many small flowers with five, white petals per flower. The flowers are radial, but flowers in the periphery of the umbel are a little bit larger than the flowers in the center.

H. sphondylium - inflorescence

All in all, the flowers create a larger, fake flower, which attracts pollinators like bees and beetles. Since the nectar isn't very deep, H. sphondylium is visited by many different pollinators, because they doesn't need a long proboscis.

H. sphondylium - flowers; the flowers in the periphery
are larger than the flowers in the center

Flowering time is between June and September and the ripe fruit is a Achene. This is a special form of the nut with double wings. So, the ripe fruit is able to fly with the wind for spreading.

H. sphondylium - double achenes wth wings

Unlike H. mantegazzianum, H. sphondylium isn't so dangerous and its liquid doesn't caused serious burns and injuries. However, the liquid of H. sphondylium can caused itchy skin irritations.

H. sphondylium - leaf

2) Habitat

Unlike H. manzegazzium, H. shpondylium is native to Middle-Europe and not a Neophyte. It can be found e. g. on pastures, meadows and along creeks but also on ruderal wastelands, if the soil is deep enough for the roots. Other common habitats are riparian forests or ditches. H. sphondylium prefers fresh and nutrient-rich places and a loose soil. It's typical for oceanic regions with wet winters and summers, which are mild in the average.

H. sphondylium - pastures and floodplains are typical

The plant is a little bit toxic, but young plants aren't. So, young individuals of H. sphondylium can be used as vegetable or fodder.