Split the vanilla pod lengthwise with a paring knife and, using the back of your knife, scrape out the seeds from inside. Add scraped seeds and pod into a medium-sized saucepan.
Add chopped rhubarb, honey, water, lemon juice, star anise, cinnamon, and ginger slices. Put the saucepan over medium heat and bring to a boil. Lower heat and simmer for 3–5 minutes, or until rhubarb starts to soften.
Stir in berries and cherries and continue to simmer for another 5 minutes, stirring occasionally. Rhubarb and berries will break down. Cherries should remain intact but tender.
Remove from heat and stir in the orange flower water, oil or zest (if using). Remove the vanilla pod, cinnamon stick, and star anise. Serve warm or cold. Store in an airtight container in the fridge for a week, or freeze.