Friday, October 10, 2008

Ragweed, Part 2 (Plants That Make Us Sneeze)

On September 22nd I published a post from the table in our Rotary Hotel room in Houston. I didn't have my iPhoto Library there and so didn't have many of the photographs I had taken for the post, so here they are in PART 2. I also took a few this morning which are included.

The outstanding characteristic of the Ragweed group of plants is that their flowers don't look like flowers as we usually think of them. The flowers that stand out have colorful petals in many interesting shapes, and some yellow pollen on stalks in the center, along with the female part which is called the pistil, which is made up of a stigma, at the top, and a style, which is a slender stalk which connects to the ovary, where the seeds will develop. The male and female flowers of ragweed are seperate and different looking but on the same plant.

I'm including some pictures of the plants in the field.

Narrowleaf Sumpweed (Iva angustifolia) is often so thick that from a distance it looks like a grass. As a matter of fact I've had people point to it and say, "Wow, you still have green grass growing."

Here at the Chiroptorium there is little growing in this picture besides Sumpweed.

This photograph was taken on the seat of our truck when it was freshly picked. You can see the male flower parts hanging down in this one, but in the scan (see September 22nd post of this Blog about ragweeds) of sumpweed the flowers are not yet open.

This photo which is a close-up of the plant in the field, you can see the male flowers clearly.

Western Ragweed (Ambrosia psiiilostachya) is not a large plant (1 to 2.5 feet tall). In this photo you can see Frog Fruit in the foregound, close to the ground. Behind it are grasses. The male flower heads are on the spike at the top of the plant. The female flowers are below the stalk in the axils of leaves.

The male flowers of this Western Ragweed plant have green caps and the flowers hang below, thus allowing the pollen to fall down and pollinate the female flowers below, or be caught in the wind and blow to other plants.

Giant Ragweed (Ambrosia trifida) can be huge, and I have seen it in wet years reach more than 9 feet tall. In wet soils in creek beds, it can become a jungle. In a reference book I have, "Illustrated Flora of North Central Texas" it says that Giant Ragweed can be up to 5 meters tall (15+ feet). This year it was only 5.5 feet tall here at the ranch.

If you look at this leaf enlarged (just click on the photo) you can see yellow pollen on the surface of the leaf along the main vein in the center of each lobe. Giant Ragweed's specific name "trifida" comes from the 3 large lobes on most leaves. The Genus name "Ambrosia" is from ancient mythology and is known as a delicious tasting food of the Gods which gives them immortality. It is hard to imagine that Ragweed would be considered tasty enough to qualify as food of the gods. However, it probably refers to its tenacity as a kind of immortality for the plant. That would certainly make sense to anyone who has tried to get rid of it.

The male flowers can be so full of pollen that it falls off with the slightest breeze and the official pollen count on the evening news is up in the HIGH category.

The female flowers are greenish and look quite different than the male yellowish flowers full of pollen under their green cap. This scan has male flowers at the top half, and female flowers in the bottom half. This is a Western Ragweed plant.

Here are 5 seeds from a Western Ragweed plant. I haven't looked at enough of them to say if these are characteristic of members of the Ambrosia genus.

As the cool fronts from up north come to Texas during the fall, the amount of Ragweed pollen in the air drops and we suffer less from allergies to it. Enjoy the cool clean air while you can, because in a few months we'll have cedar pollen to sneeze to. Aaachooo!

Photos and scans are by Margaret Bamberger during September and early October.

1 comment:

Charles said...

Margaret,
Thank you for the continuing education. I recall in my youth in Oklahoma when we did a lot of quail hunting, the quail relished feeding on ragweed seed. Many times their craw (sp?) would be packed full of these seeds (black as I recall). So the ragweed was a very valuable plant for wildlife food, especially quail, meadowlarks, etc. Thanks for the up close and personal photos.