What plant is characterized by a purple/pink flower spike blooming from July to August?

The plant characterized by a purple/pink flower spike blooming from July to August is purple loosestrife. This perennial herb is known for its vibrant, towering spikes of flowers that can dramatically impact wetland ecosystems. It typically blooms from early to late summer, reaching its peak between July and August, which aligns perfectly with the description provided in the question.

Purple loosestrife is also significant because it is considered an invasive species in many areas, outcompeting native plants and altering habitats. Proper identification of this plant is important for effective management strategies in aquatic environments.

In contrast, watershield is known for its floating leaves and does not exhibit purple/pink flower spikes; duckweed is a small, floating plant that bears small green flowers and is not characterized by spikes; and American lotus has large, distinctive white to yellow flowers that differ significantly in appearance and bloom time.