Dienstag, 27. November 2012

Plant of the Day (November 17th, 2012) - Callistemon phoeniceus Lindl.

After a longer break, which was intended to give my last article about the orange and lemon a little bit more attention, it's time for a new “Plant of the Day” Article. This time, I want to show you a new exotic plant, which grows not wild in the northern hemisphere. This species is Callistemon phoeniceus Lindl. from the Mytraceae family. In English, this plant is known as “Lesser Bottlebrush” or “Fiery Bottlebrush” while in German, the species is known as “Purpurroter Zylinderputzer” (“purple silk-hat”).

C. phoeniceus - habitus

C. phoeniceus is a small tree or scrub, which can reach heights between 1 and 6 metres (3.3 to 19.7 feet). It grows upright but the branches are overhanging. The bark is grey and slightly textured while the leaves are narrow and laceolate. They are arranged in an alternating leaf-pattern and contain some essentials oils, which give them a aromatic smell. They have a darker green colour and are between 3 and 7 centimetres long.

C. phoeniceus - leaves, branches and fruits

The most distinctive feature of C. phoeniceus (and other species from the genus Callistemon) are the inflorescence, which are long spikes in the axillary of small bracts.

The actual flowers are rather inconspicuous with small crème-white petals and a similar looking calyx. However, the most interesting feature of the flowers are their long, fiery red filaments of the stamens, through which the whole inflorescence looks like a blazing red brush. This is also the reason for the name “bottlebrush”.
  
C. phoeniceus - inflorescence (f = filament; a = anther;
c = calyx; p = petal)

Flowering time is between November and December (springtime on the Southern Hemisphere) and a second time in January.
 
C. phoeniceus - fruit

The ripe fruits are hard, woody capsules with small seeds within. C. phoeniceus is a pyrophyte; a plant, which uses wildfires for spreading. The fruits remain at the plant until a wildfire destroy the vegetation around them. Without any competitors, the seeds can now sprout and re-colonize the burned areal. Pyrophytes are very common in hot regions, where wildfires are frequent events.

 C. phoeniceus - bark

Like the most species from the genus Callistemon, C. phoeniceus is native to Australia. However, it's one of only two species, which are native in South West Australia (the other one is Callistemon glaucus (Bonpl.) Sweet). It grows on sandy soils on laterite and prefers moist but also well drained places. So, C. phoeniceus can be found e. g. at riversides or in swamps. The species s also a populare ornamental tree because it tolerates a fresh to cold climate.

Sonntag, 18. November 2012

Plants of the Day (November 18th, 2012) - Citrus x aurantium L. and Citrus limon L.

This time, I want to introduce you two different and very popular plants to you. Both are crops and use for many different purposes. This plants are Citrus x aurantium L. and the other one is Citrus x limon L., which are both members of the Rutaceae family. In German, the first species is known as “Orange” or “Apfelsine” and the second species as “Zitrone” oder “Limone”. In English, C. x aurantium is known as “Orange Tree” and C. x limon as “Lemon Tree”.

C. x aurantium - habitus

C. x auratium is a medium seized tree, which can reach a maximum height of 10 metres (32.8 feet). It has a uniform canopy, which is richly branched. The branches are covered with thin spines. However, these spines are blunt and not piercing. The leaves are arranged in the alternating leaf-pattern. The leaf-blade is inverted egg-shaped and has a strong, dark-green colour. All leaves have a long, dark petiole

C. x limon - habitus 

The lemon tree is smaller and reach average heights between 5 and 7 metres (16.4 to 22.9 feet), what depends on the sort. The branches are also covered with blunt thorns, but the leaves are more laceolate. Both species are evergreen tree

C. aurantium - young fruits & leaves

The inflorescences of both species are racemes with only a few flowers per raceme. The flowers of C. x aurantium consists of five, fused sepals and five white petals. The also white stamens form a tubular structure around the stylus. The yellow stigma is very thick and stands out from the stylus. Flowering time is between February and June in Europe and from April to May in China.

C. x limon - flower

The inflorescence and flowers of C. x limon look similar. However, the colour of petals is more dirty white. In addition, the flowers of the lemon tree exude a stricter, more putrid smell.

Pollinators are insects but Anemophily and self-polination is also possible. The last method is very useful in breeding. 

C. aurantium - ripe fruit 

Both species are easy to recognize by their distinctive fruits: the orange of C. x aurantium and the lemon of C. x limon. In both cases, the ripe fruit are berries, which consist of three layers: Endoocarp, Mesocarp and Exocarp.

  1. The endocarp is subdivided into a few chambers, which contains the seeds . These chambers (10 to 13 at the Orange and 8 to 10 at the Lemon) are drained by many, thin channels, which have a yellow-green to red colour and contain the fruit juice. 
     
  2. The mesocarp of both plants is a bright white layer, which encircles the whole inner fruit. Through its colour, the mescorarp is also called “Albedo”.
  1. The endocarp (Flavedo) is the thin, outer layer, which protects the fruit and is responsible for the attraction of potential distributors. It has a green colour first but become yellow (lemon) or orange (orange) later

The fruits of species from the Genus Citrus contain a large amount of Vitamin C and Citric Acid, which give the fruits their characteristic, sour taste.

C. x limon - young fruit

As the x in the name suggest, both species aren't natural plants but hybrids. C. x aurantium is a hybrid between Citrus reticulata Blanco (Mandarin orange) and Citrus maxima (Burm.) Merr. (Pomelo), while the Lemon is a hybrid between C. x aurantium and Citrus medica L. (Citron).

Both species were first bred in China and India in ancient times (but the true origin is unknown). Later, they were brought to South Europe and Arabia by the Moors. Portuguese merchants like Vasco da Gama (1469 - 1524) brought it to Portugal later. Today, both plants belongs to the most cultivated plants on earth (especially the orange).

Montag, 12. November 2012

Plant of the Day (November 12nd, 2012) - Hordeum jubatum L.

After a long time, I want to introduce a new grass. This grass is Hordeum jubatum L. from the Poaceae family. In German, this plant is known as “Mähnen-Gerste” and in English as “Foxtail Barley”.

H. jubatum - habitus

It a perennial grass, which can reach heights between 20 and 50 centimetres (7.9 to 19.7 inches). The stalk grows upright to slightly bended. The long and narrow leaves are hairy on both sides and have a bright green colour. They are also overhanging.

 H. jubatum - inflorescence (here you can see
the long awns)

The inflorescence are long, overhanging ears. Young ears have a silver colour, which become beige with age. Also characteristic is the red stitch of older ears, what could also be a reason for the name “foxtail barley” (because the ears look like a foxtail).

H. jubatum - habitus

The spikelets (“Ährchen”) of the ears are largely sterile; only one flower is fertile. This flower is also the only one with a stalk. As with the most species from the Genus Hordeum the lemma (“Deckspelze”) of H, jubatum has a long awn (“Granne”), which can reach a maximum length of nearly 8 centimetres.

Flowering time is during summer month. The ripe fruit is the typical one seeded nut of the Poaceae (“Karyopse”).

H. jubatum - inflorescence

In Europe, H. jubatum is an Neophyte. Its natural areal was North America (Canada) and East-Asia (Siberia) but as a popular garden plant, it was also imported to Europe and other parts of the World. From this gardens it started to grow wild later and can now be found at roadsides, construction sides or ruderal wastelands. It prefers loose soils and fresh to wet places.

H. jubatum tolerates much salt. Therefore, the species also benefits from the salt spreaders during winter, which caused a higher content of salt in the soil beside roadsides.

Mittwoch, 7. November 2012

Plant of the Day (November 7th, 2012) - Galeopsis tetrahit L.

The species, which I want to show you today is Galeopsis tetrahit L. from the Lamiaceae family. In German, it's known as “Gemeiner Hohlzahn” and in English, it's called “Common hemp nettle”.

G. tetrahit - habitus

It's a small, annual plant, which can reach heights between 10 and 30 centimetres (sometimes 50 centimetres) which corresponds to 3.9 ton 11.8 (19.9) inches. The stalk grows upright and much thickened at the nodes. The nodes are covered with many bristles.

G. tetrahit - thickened node with bristles

The leaves are lanceolate to egg-shaped an follow the decussate leaf-pattern. The have a strong serrated or lobed margin and are bald. The also have a short petiole. 

G. tetrahit - leaf

The inflorescences are whorls, which are located in the axillary of the upper leaves. The petals are green and covered with bristles. They are also very pointed. So, the Calyx of G. tetrahit is very pungent (s. pictures). The petals form the typical, cygomorphic “lip” of the Lamiaceae and have a pink colour but can also be purple or even white. The centre is yellow.

G. tetrahit - calyx

Flowering time is between June and October. The primary pollinators are bees or bumblebees. two special humps on the lower lip cause the head of the insect to the nectar. These two humps, which looks like teeth, are typical for the Genus Galeopsis and also the reason for the German Name “Hohlzahn” (what means “hollow tooth”).

G. tetrahit - flowers with humbs (arrow)

The ripe fruits are the typical chiusa (“Klausen” in German), which are unique for the Lamiaceae and the Boraginaceae. Animals remain at the spiny calyx and hurl the fruit when they rid themselves.

G. tetrahit is a very common plant in Europa but can also be found as neophyte in North America. It grows on dry and stony places and prefers nutrient rich soils (it's also a indicator for nitrogen). It can be found on ruderal wastelands, slopes and at roadsides and railroad tracks. Originally, the species is a natural interbreed between two other plant of the Genus Galeopsis (Galeopsis pubescens Bess. Fries and Galeopsis speciosa Mill.

Donnerstag, 1. November 2012

Plant of the Day (November 1st, 2012) - Echium vulgare L.

This time, I want to show you Echium vulgare L. This species belongs to the Boraginaceae family and is known as “Gemeiner Natternkopf” in German and “Viper's Bugloss” or “Blueweed”.

  E. vulgare - habitus

It's a biennial plant, which can reach heights between 25 and 200 centimetres (9.8 to 78.7 inches). The round stalk grows upright and is covered with many bristles, what is typical for the Boraginaceae. The same also applies for the leaves, which are lanceolate and about 10 centimetres long.

E. vulgare - flower and bristles

The inflorescence is a single, compact panicle, which is also called thyrse. The flowers are funnel-shaped and look like the maw of a viper, what is also the reason for the English and the German name (“Natternkopf” means “Viper's Head”). The petals are pink first but become deep purple later. Flowering time is between May and September.

  E. vulgare -flower

The ripe fruits are small nuts, which disintegrates into four small fruits. This type of fruit is called chiusa (Klausen in German) and is an unique feature of the Boraginaceae and the Lamiaceae.

  E. vulgare -habitus

E. vulgare is native to Europa and West Asia but can also be found as neophyte in North America. It grows on dry and stony places. So, it can be found on ruderal wastelands, slopes and at roadsides and railroad tracks. The species is also very popular for apiarists, because the flowers are rich of nectar.

All parts of E. vulgare contain a special types of alkaloids: the Pyrrolizidine. These alkaloids are a toxic and can cause liver damage.