I grow a number of plants that bloom at night, including regular four o'clocks (Mirabilis jalapa) and Epiphyllum strictum. The former have been blooming continuously since July, and the latter is currently producing its third flush of flowers this summer. Two more species have come into bloom more recently. The sweet four o'clock (Mirabilis longiflora) has been flowering for a couple of weeks, but the buds open so late in the day that it is a challenge to get a picture before it gets dark. Meanwhile the moonflower (Ipomoea alba) just began blooming three days ago.
Sweet four o'clock (Mirabilis jalapa)
Moonflower (Ipomoea alba)
Unfortunately, the moonflowers do not really get going until the weather gets really hot, and do not set buds until the days get short enough again. As a result, their season here in New England is quite short. However, even if I only get a handful of flowers each year, I think those huge silvery discs are well worth the minimal effort of planting a few seeds in late May and watering and fertilizing the plants through the summer.