All too often, the best things in life show up when we're not looking and — in the case of night-blooming cacti — they don't stick around for long. To get scientific: Night-blooming cereus refers to a number of flowering ceroid cacti, which include a variety with buds that bloom only at night. The flowers are usually lightly colored and very fragrant, but you won't spot or smell them if you're more concerned with catching up on your Zs. By morning, they've often wilted and disappeared. If you're not planning on growing your own or running out into the desert in the middle of the night, your best bet might be a flashlight tour (May through August) at the Desert Botanical Garden. There, you can catch the bloom of the Peniocereus greggii, or Queen of the Night cacti, and your guide will know just when and where to look.