The Trolberg Winter Festival is an annual festival held in the city of Trolberg to celebrate the blooming of the Sonstansil Tree; a rare event that only happens once a year. The tree blooms with glowing, orange flowers, that light up the entire tree.
The celebration shares a lot of similarities with Christmas. People like to decorate their homes with lights and plants, and gifts are exchanged during the blooming. In the days before the blooming, there is a market. The Sparrow Scouts sell their vegetable broth here.
The book "Hilda and the Time Worm" gives a more detailed schedule of the festival:
- The buds of the Sonstansil tree appear on the first day of the Winter Festival
- They open gradually during the three nights of the festival
- When the last bud opens, the flowers begin to glow in the dark, an event known in Trolberg as the Big Glow
- The morning after the Big Glow, everybody throws parties and gives presents.