“The U.S. Fish and Wildlife Service suggests that people could plant a garden or add a flowering tree or bush to yards and avoid using pesticide, to help increase the rusty-patched bumblebee population. Leaving some sections of the yard unmowed in summer and unraked in fall can also help since bumblebees need a good place to make their nests and spend the winter. People could also leave standing plant stems in gardens and flower beds in winter.”
Everyone can help! Even a potted plant on a balcony can help.