A recent study found that urban areas can offer hotspots of urban floral diversity. Stating further how the individual gardener has an important role to play in maintaining the population size of many different pollinators.
‘Urban nectar is supplied by a diverse community of flowering plants, heavily comprised of non‐native species. Residential gardens are the key land use underpinning nectar sugar production within urban landscapes, providing both an abundance and diversity of floral resources’ – Quantifying nectar production by flowering plants in urban and rural landscapes

Sources: