The super-exponential growth of digital data world-wide is matched by personal digital archives containing songs, ebooks, audio books, photos, movies, textual documents, and documents of other media types. For many types of media it is usually a lot easier to add items than to keep archives from falling into disarray and incurring data loss. The overhead of maintaining these personal archives frequently surpasses the time and patience their owners are willing to dedicate to this important task. The promise of gamification in this context is to significantly extend the willingness to maintain personal archives by enhancing the experience of personal archive management. In this paper we focus on a subcategory of personal archives which we call private archives. These are archives that for a variety of reasons the owner does not want to make available online and which consequently limits archive maintenance to an individual activity and does not allow any form of crowdsourcing out of fear for unwanted information leaks. As an example of private digital archive maintenance gamification we describe InfoGarden, a casual game that turns document tagging into an individual activity of (metaphorically) weeding a garden and protecting plants from gophers and includes a reward system that encourages orthogonal tag usage. The paper concludes with lessons learned and summarizes remaining challenges.