The veins on these leaves can be in many patterns. Roots can be fibrous or tap. Broadleaf seedlings have two cotyledons, or leaves, that come out of the seed. Common broadleaf weeds include lambsquarters, pigweed, velvetleaf, ragweed. They are long and thin, and the veins run parallel to the length of the leaf.
Grasses have fibrous root systems.
Grass seedlings send up one rolled leaf, or spike. The growing point of grasses is at the base of the plants. If the top of the leaves is cut off, often the leaf will just keep growing as the new growth on bottom pushes the old growth higher. New leaves come from the base of the plants. Common grass weeds include foxtail, crabgrass, and quackgrass.