The Big Book of Practical Spells: Everyday Magic That Works - Judika Illes 2016

Potpourri
Botanicals
Other powers: your Magic Allies

Commonly disguised as room freshener and typically made from synthetic substances, colors, and even fragrance, potpourri's origins lie in ancient botanical magic. Essentially incense that won't be burnt, fragrant plant materials were carefully combined. Rather than placed in open bowls, they were closed within airtight boxes. When a hit of fragrance was desired, a blast of power or intensity, the box would be opened and the fragrance inhaled. Different potpourris were created to invoke different effects: individual formulas are listed among the spells. Potpourri can also be simmered on the stove, allowing the fragrance to waft throughout the surrounding area. This method harnesses the power of all four elements: air, earth, fire and water. Fine simmering potpourri can be very simple: a few cinnamon sticks and a handful of whole cloves, for example.

Herbs may be purchased already dried. Sources are listed in the Appendix. However, it's very simple to dry fresh herbs. Hang them upside down in small bunches, so that they are not too crowded. Use professional herb dryers that look like horizontal ladders, or attach the bunches to a wire hanger. Let them hang, out of direct sunlight, in a well-ventilated area until dry.