Field Notes April 29, 2010; dayflower, fall panicum, hemp sesbania, jointvetch, Texasweed

Fall Panicum ligule

At right is a photograph of the ligule of Fall Panicum.  It technically is membraneous but fringed with hairs.

Fall Panicum leaf surface

The upper leaf surface of Fall Panicum is glabrous, that is, it has no hairs.  Sometimes literature simply refers to a smooth leaf when hairs are absent.

Pubescence on lower surface of leaf

The lower surface of the leaf at right has pubsecence on it.  The seedline looks like Fall Panicum, but Fall Panicum is not supposed to have these hairs.

Pubescence on leaf sheath

The leaf sheath of the same seedling is also hairy.  This is a 4 leaf seedling which might have some bearing on the problem.  I will monitor this plant later in the season to see if it is indeed Fall Panicum or another species.

Jointvetch seedling

The Jointvetch seedling at right can be separated from Hemp Sesbania because its first true leaf is compound.  A compound leaf is one composed of tiny leaflets instead of a single blade.  Leaves like the ones at right are said to be pinnately compound.  Pinnate means they resemble a feather.

Hemp Sesbania seedling

At right is a Hemp Sesbania seedling.  The two leaves pointing left and right are actually seed leaves or cotyledons.  The first true leaf points toward the top of the photograph.  Unlike the second true leaf which points down, the first true leaf is simple.  All other leaves will be compound.  This characteristic of the first true leaf is a reliable tool to separate Hemp Sesbania from Jointvetch.

one leaf Dayflower

When it emerges from the soil Dayflower resembles a grass seedling.  However, there is no clear cut collar at the base of the leaf and the leaf has a fleshy texture.

Texasweed in cotyledon stage

Texasweed is known by several common names including Mexican weed.  The two leaves shown here are not true leaves, they are seed leaves or cotyledons.  Often herbicides do not work well on it in this stage.


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