Xanthium strumarium (Common cocklebur)
Image credit: Sven BrandsmaIdentification tips
Tip #1: xanthos comes from Greek, yellow and stanza means "cushion as swelling" in reference to seed pods. I confess that the name is not too difficult to make yellow pad analogy, but the image I did got very bad ðŸ˜.
Plant shape
2º Identification tip: is an annual plant that produces a prickly and oblong characteristic capsule.
Leaves
3º Identification tip: alternating sheets. They are heart-shaped, with well rounded bases and wide tips. Its toothed margins, while the upper surface has a sandpaper texture. Each leaf has a long petiole, usually reddish green or reddish they usually have short white hairs.
Stem
4º Identification tip: the stems are round. They are often stained with purple and have short white hair strewn across the surface.
Flowers
5º Identification tip: the flowers are given in racemes each set of flowers develops from the armpit of each upper leaf. In addition, the central stem ends in a raceme, similar to the racemes of the underarms of the leaves. Because the common Cocklebur is monoic, each racemo produces several male composite flowers along the upper half, while several female composite flowers occur in the lower half.
Seeds
6º Identification tip: the seeds are large and are involved in the capsules being difficult to separate, so the identification is given by the capsule.
Capsula
7º Identification tip: the capsule is called bur, it is ovoid, green, turning yellow and then brown in axillary curls with stems. Each bur has two strong, curved or straight horns and is covered with hook-shaped spines.
Seedlings - the terror of all
8º Identification tip: relatively large, linear to oblong waxy cotyledons help distinguish this weed in the early stages of development. The first true leaves are not alternated and heart-shaped.
Reference
https://www.illinoiswildflowers.info/weeds/plants/cocklebur.htm