This dataset consists of occurrence and cover class observations for problematic invasive plants (so-called “problematic plants”) in the National Park Service Heartland Inventory and Monitoring Network Parks. The dataset includes approximately 35,000 individual cover class estimates covering over 120 problematic plant species observed at 13 NPS park units taken between 2006 and 2022. Problematic plant species include invasive, exotic, and harmful plant species. They fragment native ecosystems, displace native plants and animals and alter ecosystem function. In National Parks, such species negatively affect park resources and visitor enjoyment by altering landscapes and fire regimes, reducing native plant and animal habitat, and increasing trail maintenance needs. Recognizing these challenges, Heartland Inventory and Monitoring (I&M) Network parks identified problematic plants as the highest-ranking vital sign across the network. The goals and objectives associated with this dataset are described in the protocol - Kull KA, Young CC, Haack-Gaynor JL, Morrison LW, DeBacker MD. 2022. Problematic plant monitoring protocol for the Heartland Inventory and Monitoring Network: Narrative, version 2.0. Natural Resource Report. NPS/HTLN/NRR—2022/2376. National Park Service. Fort Collins, Colorado. https://doi.org/10.36967/nrr-2293355