YOUNG WATERHEMP: Here are young waterhemp plants growing in individual pots in a greenhouse. Note the shape of the leaves.
WATERHEMP LEAVES: The leaves on waterhemp plants have short petioles. That helps distinguish them from Palmer amaranth early in the season.
SAWTOOTH LEAF EDGES: This particular marestail plant has distinctive, rather deep-lobed sawtooth edges. Many marestail seen in the field have a much more subtle sawtooth edge on leaves.
CATCH BEFORE BOLT: What you don’t want are marestail plants as tall as the one sticking out from the crowd in this photo, Purdue’s Bill Johnson says. Catch them before they bolt and shoot taller.
SMALL PALMER: Not many people likely find Palmer amaranth at this size in the field. If you’ve never seen this and they’re in your area, perhaps you need to start scouting sooner, Johnson says.
LONG LEAF ATTACHMENT: The petiole that attaches the leaf to the stem is much longer on Palmer amaranth plants (shown) compared to waterhemp, a close relative.
YOUNG RAGWEED: Note the fleshy cotyledons (rounded leaves) on these young giant ragweed plants. They’re just as described in the Purdue Corn & Soybean Field Guide. If you’re scouting early, you will find this stage of growth.
CHECK HEIGHT: Here is a young giant ragweed you likely recognize quickly. It might be approaching maximum height for control recommended on some herbicide labels.
ROUNDED LEAF: This common ragweed is still small enough that you can find a rounded cotyledon on one side. Become accustomed to recognizing common ragweed at this stage, Johnson says.
TYPICAL PLANT: Most people can recognize common ragweed and tell it from giant ragweed at this stage of growth.
LIGHTER COLOR: Common ragweed may not always be dark green. Depending upon growing conditions and how wet soils are, you may find lighter-colored, yellowish-plants like these.