Thursday, June 16, 2011

An Overview of Ohio Dogbane and Milkweed Species (part 2 of 3): Milkweed Species

Well, last night I posted some information on how to tell different species of dogbane apart. Today I will give some information about Ohio-native milkweed species, and how to tell them apart.

Milkweed is known well for its "milky" sap. Milkweed tends to be rather tall, up to 3-6 feet tall. Its leaves can be up to 6 inches long or longer. The vein patterns of milkweed leaves seem to form a series of "loops" Flowers generally are a quarter-inch long, bell-shaped, and consist of 5 petals. If the stem or leaf is ruptured, it will emit a "milky" sap, thus the name. In Ohio, there are 4 types of milkweed I have to talk about: butterfly milkweed, common milkweed, Sullivant's milkweed, and swamp milkweed.

Butterfly Milkweed
Butterfly milkweed, also called butterfly weed, is really easy to distinguish once it has flowered because it has clusters of vibrant orange flowers. Generally butterfly weed will grow from 1-3 feet tall. The leaves of butterfly weed are alternate, although they sometimes can be opposite, and vary in sizes, anywhere from 2 to 6 inches long, and are really narrow. The undersides of the leaves are unusually harry. Stems are very leafy and dark red/brown in color. 

Common Milkweed
Common milkweed is a rather tall plant, growing up to six feet tall. Its leaves are very large too, the leaves are up to 8 inches long and are fat, forming an oval with a "tip" at the end. The undersides of the leaves of common milkweed tend to be pale green compared to the top side, and the underside of the leaf tends to be hairy compared to the top. Stems tend to be greenish in color, and are hollow. Common milkweed doesn't branch, however numerous stems may emerge from a common root crown. The stem tends to be covered with short hairs. Flowers of common milkweed tend to be half-inch wide purple flowers that form a 2 inch wide ball-shaped cluster. The flowers have a sweet odor. Common milkweed is easy to tell apart from butterfly weed because the flowers are purple instead of orange, the stem is greenish in color, and the leaves are oval-shaped, rather than long and narrow.

Sullivant's Milkweed
Sullivant's milkweed is very similar to distinguish from common milkweed. They are both similar in height and their leaves look nearly identical. Even the flowers look identical. Sullivant's milkweed is rare, whereas common milkweed is, well, common. Generally, the presence of Sullivant's milkweed on a field indicates that it is a high quality field. The easiest way to tell them apart is by looking at the leaves. Common milkweed leaves generally form horizontally from the stem. Leaves on Sullivant's milkweed actually are angled upwards. Another way to tell them apart by their leaves is to look at their central veins. The central vein in a leaf of common milkweed is generally a pale green, however there may be a reddish/pinkish tint to it. With Sullivant's milkweed, the entire central vein is a distinct shade of pink. A last, and more difficult, way to tell them apart is by looking at their seed pods. The seed pods of common milkweed are generally rough, and have bumps and spikes. Seed pods of Sullivant's milkweed tend to be smooth, and almost waxy.

Swamp Milkweed
The last species of milkweed I would like to talk about today is swamp milkweed. Swamp milkweed is shorter, only 1-4 feet tall. Leaves of swamp milkweed are long, up to 8 inches long, but are also narrow, no more than 2 inches wide. It is easy to distinguish from common milkweed and Sullivant's milkweed, but it does resemble butterfly weed quite a bit. The first easy way to tell swamp milkweed apart from butterfly weed is that swamp milkweed has pinkish-purple flowers, whereas butterfly weed has vibrant orange flowers. The stem of swamp milkweed tends to be green, whereas butterfly weed has a dark red/brown stem. The leaves of swamp milkweed are smooth on both sides, whereas the leaves on butterfly weed are unusually hairy on their undersides. Leaves are also in an opposite pattern.

Well, that's all I have for today. These past two posts have been dedicated to telling different milkweed species apart from each other, and different dogbane species apart from each other. Tomorrow, I will wrap up the dogbane/milkweed segment by explaining how to tell dogbane species apart from milkweed species. Once again, the photos of milkweed posted today are not mine. Take care.

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