Your lawn can sometimes become peppered with weeds, including those with yellow flowers. Dandelions are one type of yellow-flowering weed found on lawns and turf grass throughout the United States, while other yellow-flowering weeds can appear in more specialized areas. Though dandelions only grow a few inches high, other yellow-flowering varieties can grow as much as 3 to 10 feet. Knowing what weed you are looking at will make you better understand its root system and how best to get rid of it.
Observe the weed's leaves. Dandelion leaves have noticeably wavy margins, particularly if it is an older plant. Leaves should be a darker green and anywhere from 2 to 8 inches long, though some varieties may grow as long as 16 inches. You should notice an oblong outline on the leaves, which may be slightly hairy. The lobes of the leaves should point to the center of the plant's rosette.
Look at the stems of the plant. Stems should be thin and anywhere from 2 to 6 inches high. They should also be hollow and have flowering ends.
Measure the width of the plant's flowers and take notice of the color. The flowers are anywhere from 1 1/4 to 2 inches around, with bright yellow, solitary flowers on the end of each stem.
Notice how the flowers appear on the weed. Flowers form in clusters at the end of the branches. They are bright yellow in color with four petals.
Look at the flower's fruit, depending on the season. Dandelions have a silique type of fruit, containing "beaks" on their tips with squarish cross-sections. The fruit is 1.5 mm wide and 1 inch long.
Yellow Rocket (Mustard Flower)
Look at the plant's leaves. Yellow rockets have basal leaves that are 2 to 8 inches long and are dark green and shiny in color. Leaves are lobed with one large terminal lobe and as many as four lateral lobes. The terminal lobe has a heart-shaped base. Leaves towards the top of the plant are smaller and less lobed. Also look at the leaf margins, which should be wavy and toothed.
Observe the plant's stems. Stems of the yellow rocket are smooth, erect and ridged, and branched at the top. Note that flowering stems only appear in the plant's second year of growth.
Notice how the flowers are arranged on the plant. They appear in clusters on the ends of branches. Flowers are bright yellow in color with four petals each.
Note your surroundings. Yellow rocket appears in pastures, turf grass and winter small grains, usually in the eastern and central United States.
Observe the leaves. The leaves of the bearsfoot resemble a bear's foot, hence the name. Leaves are lobed and are anywhere from 4 to 12 inches in length and width. Touch the upper surface of the leaves, which should feel rough. Also notice how the leaves fall along the stems, as they appear opposite one another going up the stem.
Take a look at the plant's stems. Stems of the bearsfoot are hollow and thin and come out of a basal perennial crown. They can reach heights of 3 to 10 ft. and sometimes appear with purplish markings.
Observe the plant's flowers. Flower should appear in clusters on the ends of erect stems, are three-quarters to 1 inch long and are a bright yellow.
Notice your surroundings. Bearsfoot appears on roadsides, in pastures, hayfields and fence rows.
Look at the plant's leaves. Larger, doubly compound leaves should appear along the bottom of the plant with singly compound, smaller upper leaves. Leaves alternate on the stems and lower compound leaves can be as much as 12 inches long and 6 inches across. They should also appear a dull green with a smooth surface and oval shape.
Observe the plant's stems. Stems of the yellow pimpernel are fleshy. loose and long with a pink tint. Also note the plant's height, which should range between 1 to 3 feet.
Note the flowers. Flowers should be bright yellow with about five petals on the leaf axils of the stems.
Notice your surroundings. Yellow pimpernels appear in shady, damp woodland areas.