Trifolium fragiferum (strawberry clover) is a recent addition to the Wisconsin flora and all information provided here is from very brief preliminary observations. It has been documented at 14 locations in Brown County, and one location each in Kewaunee County (Dykesville), Outagamie County (Shiocton), Oconto County (Little Suamico), Shawano County and one in Winnebago County (Oshkosh). The first population was discovered in 2002, for which the size of the population suggested that it had been present for several years before discovery. Based on that information and the rapid spread of the species since 2002, it appears that Trifolium fragiferum probably arrived in Brown County in the late 1990's and is spreading outward from the City of Green Bay.

Trifolium fragiferum is similar to T. repens when sterile or early in flower, but is easily distinguished when the conspicuously inflated calyx is present as fruit develops. Fortunately, the fruit develops quickly once flowering starts. Flowers tend to be more conspicuously reddish than in many T. repens populations, but there is some overlap in that regard. The flowering stalks lack cauline leaves as in Trifolium repens (i.e. the flower heads are attached to the end of a leafless stalk that arises from the creeping stolon). The two species can grow next to one another or even intermingled and I have seen T. repens, T. fragiferum and T. hybridum growing within one square meter. Keeping in mind that there is considerable variability and that there are intermediate stages of development, here is a comparison of the flowering and fruiting heads of T. fragiferum and T. repens.

The habitats for the 19 known sites (many smaller sites near vouchered populations in the City of Green Bay have not been counted) are all on grassy sites that get mowed more or less regularly. In general, it seems to occur in the same kinds of sites as T. repens. The first populations discovered were all along roadsides, but it appears to be capable of spreading through adjacent lawns quickly. As is the case with T. repens, mowing is tolerated well because the stolon runs directly along the surface of the ground, below the mower height. They also flower later than T. repens, beginning about the first of July, during a period when the cool season lawn grasses are growing more slowly and lawn mowing is not so frequent as it is in June. Soils are variable from relatively heavy soils with considerable clay content, to very sandy soils. It appears to do best in moist or even wet soils, but also appears to tolerate fairly dry conditions in some cases.

It does not appear to present a threat of becoming an invasive in natural communities, as it has not shown any tendency to grow outside of mowed areas. However it appears that it may become very widespread in lawns. The rate of spread is extremely fast and it appears that it is spread locally by lawn mowers, probably by seeds rather than vegetative propagules.