How to Identify Weeds by Leaf Shape

Print off a list of weeds common in your area. A list can be printed, according to the region of the country you live in, from the USDA database. This narrows the field of possibilities so you are only looking at weeds that grow in your area.

Look at the cotyledons, or seed leaves, on the plant. These leaves will be the bottom two leaves if the plant has multiple leaf sets, and will be the only leaves on a plant that has just emerged from the ground.

There are nine basic seed leaf shapes: round, kidney, butterfly, ovate, oval, spatulate, lanceloate, oblong and linear. Images of each leaf type are available online. Determine which leaf shape your weed has, and look at the list to determine which weeds it could be.

Observe and record the shape of mature foliage. These are any of the leaves that unfurl after the cotyledons. There are 12 basic leaf shapes: heart, lobe, spade, arrow, star, pentagon, oval, ovate, elliptical, lancelolate, oblong and spoon. Compare your leaf shape to the weeds on your regional list, and eliminate any weeds whose description does not match the leaves you have observed.

Feel the margin of the leaf, and take note of the leaf edge's texture. Possible textures include serrate, dentate, crenate, sinuate, distantly toothed, toothed and lobed. Record the data, and use it to determine what weed you are dealing with.

Look at the leaf's vein pattern. Leaves can have palmate venation, three prominent vines at the center and outer edges of the leaf or pinnate veins. Compare this information to the list.

Observe the way that the leaves attach to the stem. Leaves will either be alternate or opposite in arrangement. Alternate leaves are at distinct and different levels along the stem. Opposite have pairs of leaves at the same level on the stem.