Nyctanthes arbor-tristis L.

Har singar should not be confused with the West Indian shrub Cestrum nocturnum, also called queen of the night. Nyctanthes arbortristis literally means, night-blooming sad tree. Grows as large shrub or small tree depending on how it is trained. The large attractive leaves are rough and hairy. The sweet scented flowers are small, attractive with white petals and an orange-red tube in center and bloom profusely, opening at night and drop off in the morning, thus making a carpet of flowers in the morning. Used for worship. Needs warmth during winter months. Use well drained soil and fertilize once a month.
References
1. Sharma, L., Dhiman, M., Singh, A., Sharma MM (2021). Nyctanthes arbor-tristis L.: “An Unexplored Plant of Enormous Possibilities for Economic Revenue”. Proc. Natl. Acad. Sci., India, Sect. B Biol. Sci. 91, 241–255.
2. http://www.flowersofindia.net/catalog/slides/Har%20Singar.html