*Limitations*

Not all planning problems identified are equally relevant for every supply chain role in the sector, i.e., producers, wholesalers, and retailers. Our systematization thus presents more of a comprehensive overview rather than a dedicated systematization for specific companies. However, as vertical integration is common in the sector, the companies will typically face large parts of the planning tasks outlined within our study. Nevertheless, our contribution is not without limitations. As we have relied on expert interviews with selected managers of companies in the sector, our results cannot be seen as representative in a quantitative sense. However, by following the guidelines of Mayring [19] and reaching theoretical saturation, we believe that our presentation of planning problems represents the typical challenges that small and medium-sized companies face in ornamental horticulture. Furthermore, our findings are derived from interviewees with companies operating in the German market. This was necessary to create a unified context and to limit our data collection to a reasonable scale. As Germany is one of the largest producing horticultural markets in Europe [1,2] and has similarities with several other non-auction-driven markets, we believe that our planning matrix is also applicable to companies in other regions worldwide. Future research could, however, compare our systematization derived from the German markets to other markets. A special interest could be a comparison of auctiondriven with non-auction-driven markets, or a comparison of the situation on different continents, as horticulture is very dependent on the ecological environment.

**Author Contributions:** Conceptualization, A.H.; methodology, M.D. and A.H.; validation, M.D. and A.H.; formal analysis, M.D.; investigation, M.D.; data curation, M.D.; writing—original draft preparation, M.D. and A.H.; writing—review and editing, M.D. and A.H.; visualization, M.D.; supervision, A.H.; project administration, A.H.; funding acquisition, A.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research is part of a project called PlantGrid. The project is supported by funds from the Federal Ministry of Food and Agriculture (BMEL) based on a decision of the Parliament of the Federal Republic of Germany via the Federal Office for Agriculture and Food (BLE) within the aegis of the Innovation Support Program. The APC was funded as part of this project as well.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** We thank all participating experts for sharing their information and providing valuable sector-specific insights. We also thank the anonymous reviewers for their constructive suggestions for improving the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.
