Mark Renz, Extension Weed Specialist, UW-Madison
Now is the time of year when we start to notice vines climbing trees, crops, and even structures. While Wisconsin has over 50 plants categorizes as vines, bur (Sicyos angulatus L.) and wild (Echinocystis lobata (Michx.) Torr. & A.Gray) cucumber are two of the most common found in Wisconsin. If you see a vine that has small white flowers in August, chances are that it is one of these two species. While many characteristics are present to differentiate between the two, the easiest is to look at the leaves, as they are quite distinct. See below for pictures from the Arlington Ag. Research Station taken in Late July of this year.
Both are native annuals fairly well distributed throughout the state. While these germinate in late April to early May (seedlings look very similar to cucumber seedlings), they are usually not identified until they produce small white flowers (July-August) when vines are over 10 feet in length. Vines typically are intertwined in other plant material, making it extremely difficult to remove the entire vine. If possible, look for where the vine attaches to the soil and pull/cut the stem at this point. The remaining tissue will die as it its supply from the roots has been severed. Several herbicides are also effective, but make sure the plant it is wrapped around is tolerant to the herbicide you plan to use.
If seen in an agricultural setting I recommend managing this plant before it produces seed as these will require management in future years. If in natural or non-crop areas, admire it as unique native vegetation of Wisconsin.
For more information about wild cucumber and some great photos see: http://wimastergardener.org/?q=WildCucumber