The Midwest prairies are home to dozens of wildflowers, and many of these wildflowers have become part of the palette gardeners use to create colorful landscaping. Wild flowering plants in Illinois are favorites with gardeners because they are hardy and easy to grow. Not all Illinois purple flowering plants are native to North America. Certain species have naturalized into wild populations.
Purple violet (Violet viola), the state flower of Illinois, occurs naturally throughout the state. At home in woodlands and prairie alike, violets grow in shade or sun, preferring moist soil. They grow in clumps about 8 inches high. The clumps can be divided to make new plants, but violets also self seed. Early spring brings on the first flush of violet blossoms, with conspicuous purple flowers held above the mound of foliage. Violet blossoms are edible. They are used as garnish or in salads, and they are often sugar-coated and used as cake decorations. Once the showy flowers have faded, smaller flowers appear. The smaller, late violets are usually on short stems below the foliage. The late violet flowers look like partly open buds. They make most of the violet seeds.
Purple loosestrife (Lythrum salicaria) is a purple flowering plant that grows in Illinois. Native to Europe and Asia, it has adapted to the grassland areas of the Midwest. Purple loosestrife was brought to America by immigrants in the early 19th century as an herb and ornamental plant. The ubiquitous seeds may also have been carried in sheep's wool or in ship ballast. Purple loosestrife is a perennial, growing up to 7 feet tall. The flowers are at the tip of the stem in a long, spiked cluster. It grows in moist or wet areas, crowding out native species. Purple loosestrife is considered an invasive plant in some states. One plant produces thousands of seeds each year, many of which remain viable in the soil for many years. It can reproduce from a small piece of stem or root, and it is nearly impossible to eradicate by digging, pulling up or burning. Chemical herbicides are ineffective on purple loosestrife. Biologists have introduced beetles from Europe that feed only on purple loosestrife and in test areas this biological control method showed promise.
Summer phlox (Phlox paniculata) is native to Illinois, although botanists believe that wild populations may have crossed with cultivated varieties. Phlox is found throughout Illinois except for the extreme northwest corner of the state. Summer phlox is the largest phlox plant, maturing at 2 to 4 ft. tall with large clusters of flowers that may be white or various shades of pink or lavender. It grows in clumps along the edge of woods, where partial sun improves the flowering. Moist, rich soil is best, and phlox often grows along creeks or riverbanks. The flowers attract a number of butterflies and moths, including the rather elusive hummingbird moth and sphinx moth. The nectar is deep in the flowers, and only insects with long mouthparts can reach it. Summer phlox is also called garden phlox, because it is frequently used in flower gardens.