Plants With Spirit - NYTimes.com Twenty years ago, I made an accidental hajj to a founding site of American Druidism. We called it the Hill of Three Oaks and that's what it was. The main attractions were Ultimate Frisbee and beer - an improbable pairing, best left to the elite class of frolickers. What I didn't know at the time was that some of the first Druid gatherings in the United States also took place on the Hill of Three Oaks, at a small Minnesota prairie school called Carleton College. There, 50 years ago, a group of freethinking students discovered a way to evade Sunday's mandatory chapel service. They invented a church of their own: the Reformed Druids of North America. How this prankish act of protest turned into an earnest religious movement is a tale for another day. One simple lesson, however, is that it doesn't take much to form a genuine Druid sanctuary. Start with what you've got in the backyard, said Ellen Evert Hopman, a Druid herbalist and author. "Every tree is a church," she said. The roots of the tree go down to the Sidhe realm - the fairy domain, the underworld. The branches go up to the sky world of the gods. And the trunk is in the middle: the realm of the nature spirits, the humans and the animals. Celtic lore held the white oak to be a signpost for the otherworld, she said. During Samhain, the Druid festival devoted to the ancestors, Ms. Hopman will "make offerings to the oak tree" from her garden: dried lavender, rose petals, fruits, mushrooms. "Anything nature would like," she said. In "A Druid's Herbal of Sacred Tree Medicine" (Destiny Books, 2008), Ms. Hopman lays out the sacred properties of all the trees that make up the ogham, an inscribed and coded alphabet of the ancient Celts. If you're not ready to plant a full Druid arboretum, though, "you've got to have a hawthorn." This was an important plant for Beltane, the May Day festival. "Back in the time before the Internet," she said, "you knew it was summer because the hawthorn bloomed. That meant it was safe to send the cows up to the hills. These days, sadly, not everyone has a cow (or a hill). Yet the old gods can send signs through a more familiar device. The Druid Oracle Cards is an iPhone app from Philip Carr-Gomm, the chief of the Order of Bards, Ovates and Druids. It lists the magical properties for dozens of herbs. Can the mugwort weed on the lawn also open your third eye to prophecy? And why does that crow keep landing on the barbecue? All secrets will be revealed in the Apple store. Though you may not have stepped outside, your Druid prayer garden is almost complete. Ms. Hopman said: "The next step is some water - like a bowl of water, or a stream if you're lucky. And some kind of fire. If you have fire, water and tree, that's the full ceremonial get-up right there! Until, that is, you're ready to break ground on a stone circle.