Q Garden in Brooklyn is setting up Zoom meetings for their garden group and a WhatsApp group for gardeners to stay in touch.
For policies on the ground: they have closed their public composting program -- only in-house DIY compost for now. They are setting a cap of no more than 3 gardeners at a time, all maintaining social distancing. They posted Covid-19 precaution posters as public service announcements.
Slight correction: the garden is called Q Gardens :)