Ambrosia artemisiifolia

Ambrosia artemisiifolia

Ambrosia artemisiifolia or comon ragweed is the most widespread species of Ambrosia. I have already written about silver burr ragweed (Ambrosia chamissonis). Indeed you can see close resemblance between two different species of the same genus Ambrosia. The leaves look very similar and the tassels of flowers are common to both. But Ambrosia chamissonis grows mainly on the sea coast while Ambrosia artemisiifolia is common on the dry land. It does not mind the hot climate. Beach variety is also more prostrate while common ragweed plants grow tall.

Common ragweed flowers

The name artemisiifolia is given to the plant because the leaves resemble those of a related genus Artemisia (wormwood or sagebrush). The smell is also somewhat similar though Ambrosia have tougher leaves and bigger flowers (still very small though) that are green or yellow. An interesting thing about common ragweed is that it is supposed to be one of the major culprits of hay fever though I personally never suffered from this particular plant.

Like Artemisia, Ambrosia belongs to the Aster family (Asteraceae).

Conyza canadensis

Conyza canadensis

Conyza canadensis or horseweed is a plant that can be found in dry (and not only) areas. With Croton setiger and Ambrosia artemisiifolia it makes the big three that can be found blooming in the heat of the August on the dry plains. So what can be found about conyza?

Conyza canadensis

Other names for conyza include coltstail, marestail and butterweed. The former two are obvious for the plants's resemblance to coltstail. Note that there are plants named horsetail (Equisetum) and mare's tail (Hippuris) that are quite different from Conyza. The name butterweed is most likely given for the plants resemblance to senecio genus, which is commonly known as butterweed (among other common names).

Conyza flowers. Notice resemblance to senecio.

One interesting fact about conyza is that the plant developed resistance to herbicides. Another fact is that Zunu Indians used crushed flowers to cause sneezing by inserting plants in the nostrils.

As the name canadensis implies, conyza grows in Canada and also in Britain so it is not exclusive to hot climate though it sure strives here. During the heat the top of the plant can be seen wilting down but it straightens up when the air becomes cool.

As you can guess by looking at the flowers conyza is part of the aster family (Asteraceae).

Croton setiger

Croton setiger, commonly referred to as turkey mullein is a heat tolerant plant that is quite common in the dry area. Well, at least it's common at the area where I live right now. The plant is amazing: 100 degrees heat and full sun and it's looking nice and green. However even this hardy plant can have too much: recently I saw few species dried to a crisp from long exposure.

Croton setiger in a desert area

So the name mullein points to similarity to common mullein. Indeed, both plants have fuzzy leaves. But that's all they have in common. These two plants are not related. Common mullein's Latin name is Verbascum thapsus and it belongs to Figwort family (Scrophulariaceae). Croton is part of the Spurge family (Euphorbiaceae). The flowers are quite different too: verbascum has distinctive yellow flowers with 5 petals. Crotons's flowers are tiny and formed into clusters of sandy color.

Croton setiger close-up

Croton' leaves have pleasant smell when crushed, provided the plant is healthy. The leaves are fuzzy. here is the close-up of flowers:

Croton's flowers

Asclepias

Asclepias or milkweeds are peculiar flowers that are very easy to recognize due to their unusual shape. Asclepias as the name suggests are named after a Greek god of medicine. The common name milkweed refers to milky sap that the plant exudes if you break its leaf or stem. The plant is supposed to be medicinal.

Asclepias belong to dogbane family (Apocynaceae) among whose members we encounter species like plumeria and vinca (periwinkle). Lots of species of this family has milky juice and are toxic if ingested. Lots of plant are tropical species.

You can see the shape of the plant in the pictures. The structure of the flower remains the same in all the species though the shape of leaves and colour of flowers vary. Below you can see species of Asclepias fascicularis or narrow leaf milkweed.

Acclepias growing near the curb

Close-up of flower heads

Close-up of flowers. Notice inverted sepals.

Milkweeds are drought-tolerant and grow well in hot dry countries.