Herbaceous vegetation is a critical component of the multi-layered arrangement in historic gardens, enhancing its harmony and natural balance. Despite its numerous advantages, such as limiting weed growth, inhibiting soil degradation, and increasing biodiversity, it remains one of the most neglected components of historic gardens. The objective of this article was to present practical guidelines for the management of herbaceous vegetation in the North Landscape Garden of Wilanów Palace made for the Museum of King Jan III’s Palace at Wilanów between 2017 and 2018. Analytical studies and design works were conducted for an area of 5.3 ha. Following the principles of conservation with respect to spatial forms and landscape features with simultaneous reference to the composition of natural plant communities and preservation of the existing natural qualities, a list of 106 dominant and coexisting plant species was proposed. Herbaceous vegetation covered in total 39% of the park’s area. The identified species indicated a habitat of subcontinental oak-hornbeam forest (Tilio-Carpinetum calamagrostietosum) and willow-poplar marsh (Salici-Populetum). In addition, compositional guidelines and recommendations for implementation, care and use were specified. The correct management of herbaceous vegetation in a historic garden requires a well-thought-out design and implementation process that accounts for cultural values and habitat conditions.