Montag, 23. Dezember 2013

Montag, 16. Dezember 2013

Plant of the Day (Dezember 17th, 2013) - Euphorbia pulcherrima Wild. ex. Klotsch.

Christmas is coming and so, I decided to dedicate the Post of this week one of the most popular Christmas plants. No, I'm not speaking off a Christmas tree (however, you can find my article about Abies nordmannia,the popular Christmas tree, here), but off Euphorbia pulcherrima Willd. ex. Klotsch. from the Euphorbiaceae family. In German, this species is known as “Weihnachtsstern” (Christmas's Star). In English, the species is known as Poinsettia; named after the U. S. diplomat (and later Secretary of Defense) Joel Roberts Poinsett, who introduced the species in North America in 1825.

1) Description

First of all, it's important to differ between the natural Poinsettia and the ornamental plant. The natural form is a perennial plant or evergreen shrub, which can reach heights between 90 centimeters and 3 meters (3.0 to 10.0 feet). It grows very sweeping and is one of the most sweeping Euphorbia species. However, the stalk isn't so richly branched and the internodes are very long. In contrast to this, the internodes of the breedings are shorter and the stalk is richly branched to create a dense foliage. These sorts are also smaller.

E. pulcherrima - habitus (breeding)

In both cases, the leaf bases are lanceolate to oval. They are sitting at the end of a long petiole, which is about 8 centimeters (3 inches) long. Their margin is smooth to slightly serrated. The dorsal site has a dark green color with white leaf-veins as contrast, while the ventral site is more bright green.

E. pulcherrima - leaf

As with the most Euphorbiaceae, the inflorescence of E. pulcherrima is a Cyanthium; a large, fake “flower”, which is composed of many small flowers and bracts. In this case, the actual flowers are very inconspicuous. They are small an have a yellow to yellowish green color. Petals and sepals are missing completely. Flower are either male or female. In the most cases, the flower in the center is female, while the other flowers are male (indicated by the single stamen). There are also some lip-shaped glands at the edge of each Cyanthium. They secrete nectar to attract pollinators.

E. pulcherrima - leaf veins

So, the main attraction is made by the conspicuous bracts, which surround the flowers. Basically, they have the same shape like the normal leaves but the have a bright, red color, which creates a strong contrast towards the rest of the plant. In cultivation, other colors like pink or cream-white are also popular. Blue bracts aren't naturally. In this case, the bracts are over painted with a varnish.

 E. pulcherrima - bract

Flowering time is between November and February. E. pulcherrima is a short-day plant. That means, the bracts only become red, if they aren't exposed to sunlight more than 12 hours. So, it prefers shady places to grow (see distribution).

E. pulcherrima - Cyanthium with  1) stamens, 2) female flowers
and 3) glands

All parts of E. pulcherrima contain a milky, white juice, which is typical for the most (but not for all) Euphorbiaceae. This juice is a little bit toxic and can cause skin irritations and allergic reactions. However, the plant isn't deadly poisonous like some people say.

2) Distribution

E. pulcherrima is native to Mexico and Middle America. However, it can also be found as Neophyte in Africa and the Mediterranean. The plant prefers a warm to hot climate and grows in the undergrowth of the forests with long, warm summers. It likes shady places on a moist but not wet soil. The plant is very sensitive towards light and temperature and will wilt, if it becomes to cold.

Today, the poinsettia is one of the most popular ornamental plants of the world. It was introduced to the United States by Joel Roberts Poinsett in 1825 and in Europe by Alexander von Humboldt in 1804. Since then, many different sorts and breedings were created. The plant is very popular for Christmas-themed floral displays, because the flowering time (more accurate: Dyeing of the bracts) happens during the winter months. In addition, the arrangement of the bracts reminds at the Star of Bethlehem.

Freitag, 6. Dezember 2013

Plant of the Day (December 6th, 2013) - Lepidium latifolium L.

Pfefferkraut” (what is the literally translation of “Pepperwort”). However, there is also another plant, Satureja hortensis from the Lamiaceae, which is also known as “Pfefferkraut”. So, it's always an advantage, if you know the Latin name.

1) Description

Our species is a perennial plant, what is remarkable, because the most species from the genus Lepidium are annual or biennial plants. L. latifolium is also one of the largest plants from the Genus, because it can reach heights between 50 and 130 centimeter. It has also a widely branched rhizome. As a result, our “Pepperwort” grows in dense stocks as shrub.

L. latifolium  - habitus; on the right side,
you can also see a basal leaf with its petiole

The basal leaves are about 25 centimeters long. They are lanceolate to egg-shaped and have a long petiole. In contrast to this the upper leaves and stalks have no petiole, but sit directly on the stem. They are also smaller (between 5 and 10 centimeters in length) and more lanceolate as egg-shaped.

 L. latifolium - habitus; here, you can see flowers an 
the leaves
Another difference to other species from the Genus Lepidium are the inflorescences. While the inflorescences of the most species from this genus are dense racemes, the inflorescence of L. latifolium is a loose, width pancicle, which consists of many, small flowers. Each flower has white to cream-white petals, which are only about 2,5 millimeters long. The pods (Schote) are elliptical to round and about 2 millimeters in diameter.

L. latifolium - leaves (basal and upper leaves)

Like the most Lepidium species, L. latifolium can be used as vegetable and spice. The leaves have a intense, sharp taste, which is even stronger than the taste of the more common “garden cress” (L. sativum).

2) Distribution

L. sativum is native to Eurasia but can also be found in North America as a neophyte. In this regions, the plant is even an invasive species, which threatens Biotopes like salt marches and flood plains by its rapid spreading.
flood plains like this are a good habitus for L. latifolium
beyond the shores.

It's a salt plant, which grows on salty places on sand and clay. So, it can normally been found along the shores at beaches and dunes. In the Inland, it's rare but can also be found at flood plains or other salty places like some ruderal wastelands. We found this exemplar at the shores of the river Rhine in Duisburg-Homberg during a field trip in August 2013.