St. John’s wort (Hypericaceae) is the common name for a family of plants with showy yellow flowers. It is commonly believed that the name refers to John the Baptist, since many of the plants bloom around the time of the feast of St. John the Baptist in late June. This family is quite large, with about 700 species found worldwide. In Florida, 34 species have been documented by the University of South Florida in its Atlas of Florida Plants (Florida.PlantAtlas.usf.edu).
One of the more common plants of this family found in our area is the four-petal St. John’s wort (Hypericum tetrapetalum). It is a native perennial shrub found throughout Florida except in some of the northernmost counties. In fact, it is almost endemic, only found outside of Florida in a few counties of southern Alabama and Georgia. It grows in damp sandy soil — for example, wet flatwoods or the margins of ponds.
This plant is one of the more easily recognized St. John’s worts because of its blue-green foliage and bright lemon yellow flowers. This slender plant usually has a single erect stem that can grow to a height of 3 feet. However, there is also a prostrate form that stays low,with multiple spreading stems. The stem is smooth and hairless. The bluish-green heart-shaped leaves are opposite and attached directly to the stem. They are considered clasping, because they partly surround the stem.
The flowers, about an inch in diameter, have four petals subtended by four sepals. Two of the sepals are quite large and resemble leaves. The other two inner sepals are much narrower. In the center of the flower is the pistil surrounded by about 100 stamens. They bloom year round, but are most abundant in late spring. They are attractive to some pollinators, such as bees.
After a flower matures, the petals drop off and the sepals fold up and envelop the pistil, which then slowly develops into a seed capsule. Eventually, the capsule opens and releases many small seeds.
Some species of St. John’s wort have been used for medicinal purposes in Europe as far back as the ancient Greeks. Various species of this plant have been used to treat kidney and lung ailments and for healing of wounds.
One species, Hypericum perforatum, is used as a dietary supplement for depression. This plant is native to Europe and Asia. It has been introduced into the U.S. and is now found in most states; however, it has not taken root in Florida. The effectiveness of the supplement produced with this plant is debatable. For more information, go to http://bit.ly/2M1UlqJ.
Be sure to take time to walk through your neighborhood and look for the four-petal St. John’s wort, which is now in bloom. All of the photographs accompanying this column were taken by the author in the Deep Creek neighborhood.