Novel, first published: Analog Science Fiction / Science Fact, Oct.-Dec. 1979
A mysterious black box lands in Minnesota, and when an excited barber takes a potshot at the box, he is burned to a crisp. Along with other forms of life, a graduate student on a fishing trip is taken inside the box. The student receives a strong impression of home and that the box is somehow akin to a tree, but then the box disgorges him. News of a new satellite, which may be the mother ship, alerts the White House. Meanwhile, the visitor starts chewing up trees and spewing out bales of cellulose behind it. A shuttle confirms that the new satellite is a huge cluster of visitors waiting to come down to Earth. The government is uncertain what to do, when suddenly the visitor begins budding "babies" who start gulping down the cellulose. The visitor takes off, leaving its offspring behind.
Other visitors start landing everywhere in forests and lumberyard, but no one is actually harmed. The President chooses to sit tight and wait, despite pressures from religious cults, conservationists, and the military who covet the visitors' defense system. Just as suddenly as they came, the visitors begin leaving. In exchange for the trees, the visitors are budding biological "cars" that operate without fuel, fly through the air, and never crash. Another group is experimenting with making houses. The free cars and houses are causing economic panic, and this crisis forces international cooperation and a new economic world order. The story ends on an uneasy note - are the visitors making people, too?
Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.116-117