great manna grass, reed mannagrass, greater sweet-grass

Publié le 19 Juin 2022

great manna grass, reed mannagrass, greater sweet-grass (Glyceria maxima )
great manna grass, reed mannagrass, greater sweet-grass (Glyceria maxima )
great manna grass, reed mannagrass, greater sweet-grass (Glyceria maxima )

great manna grass, reed mannagrass, greater sweet-grass (Glyceria maxima )

I take advantage of the off-season to introduce you to this plant, which is not very attractive but is often found at the water's edge in summer.

Roland

 

Scientific name: Glyceria maxima (Hartm.) Holmb.

Its former name is Glyceria aquatica.

 

Origin of the name: "glyceros" means in Greek "sweet, sweet" in connection with the taste of the seeds that the inhabitants of the Slavic countries consumed boiled and "maxima" "large", because this plant is very large.

 

Dialect and German name: Grosses Süss grass, Wasser-Schwaden

 

English name: great manna grass, reed mannagrass, greater sweet-grass

 

Date of sighting: July 17 in Harskirchen (67)

 

Family of plants: This is the large family of Poaceae formerly called Grasses.

There are more than 12,000 species identified worldwide, including several hundred in France.

These are all those herbs that closely or remotely resemble corn, rice, sugar cane, bamboo, millet, wheat, oats or even barley.

It is THE family of primary importance at the nutritional level, all edible cereals are part of it.

It covers 40% of the terrestrial vegetation cover.

Common characters:

They are herbaceous plants with inconspicuous, non-colored flowers. Their stems, the culms, are cylindrical, hollow and have nodes from which the leaves arise.

Normally a leaf has a widened part, the blade and a narrow part, the petiole which connects it to the stem like, for example, the leaf of an apple tree.

Poaceae leaves have no true petiole and form a leaf sheath surrounding the stem from the node. The leaf blade widens as it moves away from the stem, starting at the ligule. It then becomes visible to  the observer.

Leave and  seeds of great manna grass, reed mannagrass, greater sweet-grass (Glyceria maxima )
Leave and  seeds of great manna grass, reed mannagrass, greater sweet-grass (Glyceria maxima )
Leave and  seeds of great manna grass, reed mannagrass, greater sweet-grass (Glyceria maxima )
Leave and  seeds of great manna grass, reed mannagrass, greater sweet-grass (Glyceria maxima )

Leave and seeds of great manna grass, reed mannagrass, greater sweet-grass (Glyceria maxima )

Flowering: May to August

 

Inflorescence: all the flowers of this glyceria are a long panicle of 20 to 40 cm with spreading and stiff branches joined by 5 to 10.

The green then yellow-brown to purple spikelets, 4 to 10 mm in length, are very numerous and compressed. They hide 5 to 8 flowers with 3 stamens and stigmas.

The flowers at the top of the spikelet are sterile.

Each spikelet has 2 glumes which are the outer envelopes. The outer lemma measures 3 to 4 mm and has 7 veins but no ridges as in other grasses.

 

The composition and arrangement of the spikelets is typical of each Poaceae and requires a good magnifying glass for observation.

 

 

Pollination: anemophilous plants (pollination is done by the wind).

 

Possible confusion: with other poaceae but remains easy to identify.

 

Habitat: This plant likes still or slow-flowing water with nutrient-rich muddy bottoms. She also needs sun. It often grows in “wet” habitats such as along slow flowing river banks, drainage ditches, ponds and lakes all over Europe and as far away as Siberia.

This plant grows in water up to 75 cm deep and sometimes more.

 

Fruit: it is a very small and light seed of 1.5 to 5 mm disseminated by the wind (anemochory) and the animals (zoochory) to which it clings thanks to edges on its periphery

 

Protection: very common plant in some regions like ours, rarer in others like Occitanie and Limousin. In this region it is classified as vulnerable and in Aquitaine it is protected by law.

On other continents, without its predators in Europe and Asia, it is quickly invasive and considered a plant plague in many New World countries such as North America and Oceania. A single plant can produce up to 100 shoots and 30 m of rhizome in its first 2 years of growth. The rhizomes can sink up to 1 meter into moist soil and alone make up 40-55% of this plant's biomass, no wonder it's invasive with all those superpowers.

Phosphorus, an essential mineral needed by all plants, is the factor limiting its growth in this glyceride if it is lacking.

 

 

Food use: in the past the seeds were ground to extract flour and make a porridge. It was in the Iron Age according to the remains analyzed and from the 13th century in Poland for example. The use was gradually abandoned (nineteenth century) due to the very low harvest yield of this glyceride compared to cereals and also due to the disappearance of wetlands.

The flour obtained from it cannot be used to make bread or other leavened products.

More annoyingly, under certain age conditions, and depending on the nutrients present in the soil, this plant produces, like Sorghum, dhurrin (dhura = sorghum in Arabic). It is a complex sugar that releases cyanide during digestion;

This dhurrin has led to cases of severe poisoning in cattle. It is also a powerful insecticide secreted by the plant which limits the attacks of small critters.

 

Agricultural interest: this plant is appreciated by cattle and horses (when it is not toxic...). It therefore has fodder qualities because it is nutritious.

On the edge of rivers and ponds it protects the banks from erosion with its rhizomes in dense mats.

 

 

Horticultural use: there are certain decorative cultivars used in ornamental garden ponds.

 

Medical use: none to date.

 

Text and photos Roland Gissinger (Anab) Proofreading Bernard Weinzaepflen (Anab)

 

 

Bibliographic sources see biodiversity index

historical use of Glyceria maxima

Rédigé par ANAB

Publié dans #English files

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T
Thank you for this very informative article. Superb photos.
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A
Thank you very much Toll for this comment<br /> Roland