Japanese beetles, an invasive species, have not been eradicated despite the best efforts of Master Gardeners. They are still found in many Minnesota counties, but are most abundant in the Twin Cities metropolitan area and southeast Minnesota. The adult beetles emerge in late June or early July, feeding primarily in July and August. A good time to manage them is in the morning when they are moving slower. Gardeners are advised to pick them off or flick them into a bucket of soapy water. It's important to note that if you see a white spot on their head or back, it means they have been parasitized by the Winsome fly, a biological control agent introduced in 1923 in New Jersey. The Winsome fly has been released in Minnesota since 1998, with the majority being released at Theodore Wirth Park in Minneapolis. The fly is considered one of the more effective biological control agents for Japanese beetles, and recent research indicates that it is adapting to Minnesota's climate, including warmer winters, and its emergence is better aligned with that of the Japanese beetle's emergence. This makes the Winsome fly a very promising natural biological control for those Japanese beetles that do so much damage to our crops and ornamental plants.
Moving on to another question, powdery mildew is a common fungal disease found on many garden plants, often attacking plants that are in too much shade or planted too closely together (restricting airflow). Bee balm is one of many ornamental plants that is prone to powdery mildew. Gardeners are advised to avoid using a fungicide, as it won't cure or get rid of it. Although it is unsightly, powdery mildew does not significantly damage the plant. In the future, if gardeners add more bee balm to their gardens or want to replace what they have, they should consider varieties/cultivars that are resistant to powdery mildew, such as Monarda fistulosa (wild bergamot), Raspberry Wine, Marshall’s Delight, Jacob Cline, Claire Grace, Bee-You Bee Happy, and Bee Bright.
Regarding Sweet William, it is a biennial plant that requires two years to flower. Gardeners won't see flowers this year, but they will see them next year as long as they planted them in well-drained soil. The first year, the plant grows its roots, stems, and leaves, and the second year, it flowers, produces seeds, and then dies. If the plants are happy in their location, they will reseed and you will get plants yearly once they become established. Sweet William is a classic cottage garden plant and an excellent cut flower with a long vase life. It is hardy to zone 3.
Finally, wild Canadian ginger (Asarum canadense) is a great choice for a woodland garden. It is a Minnesota native plant found in moist woodlands and forests. It gets about 6-9 inches tall, grows best in part to full shade, and spreads by rhizomes. The leaves are heart-shaped and densely covered in soft hairs on the underside. Canadian ginger flowers in the spring, but you have to look hard to find the flower. Each plant has a single, brownish-red flower that is jug-shaped and lies on the ground at the base of the plant between two leaves. It is not related to the ginger we use for Asian cooking.
Dwarf indigobush (Amorpha nana), also known as fragrant false indigo, is a Minnesota native plant that is definitely worth looking for! It is native to most of the western half of Minnesota and Crow Wing County. In its native habitat, it is found in sunny upland prairies. This plant will not only add beauty to your landscape but is also excellent for pollinators. In early summer, dense spike clusters of indigo-colored flowers with contrasting yellow stamens cover this deciduous shrub. Small green legume pod fruits persist into winter. This is a very short shrub, growing to a mature height of one to two feet. Dwarf indigobush blooms on old wood, so if you cut it back, it will not flower until the following growing season.
