Three different kinds of claim
When you read about a plant you'll meet three things tangled together. Documented history: what people demonstrably grew, ate, traded and wrote about. Folklore: the stories and customs attached to it, which are real as folklore whether or not they're accurate. Modern correspondence: the magical association assigned to it in twentieth-century and later witchcraft writing. Keeping the three apart is most of what separates good herbal writing from bad.
How magical herb use works in practice
In everyday modern practice, plants are used as focus objects and symbols: carried in a pouch, added to a jar, simmered on the stove (keep an eye on the pot and crack a window for airflow), dried and kept, set on an altar, or grown on a windowsill. The kitchen shelf is a perfectly respectable place to start, and 'shop-bought dried herb' is not a lesser ingredient.
Substituting sensibly
Substitute on association, not appearance. If a spell asks for something you don't have, ask what it's there to represent, then pick something in your cupboard with the same meaning for you. Rosemary is widely treated as an all-purpose stand-in in modern practice. Salt, water and a written word will carry a surprising amount of work on their own.
Safety comes before symbolism
Pretty Little Wiccan covers folklore, food and magical practice, not herbal medicine, and it doesn't teach plant identification or foraging. Only eat, drink or burn correctly identified, food-safe or shop-bought ingredients, never anything foraged or identified on guesswork. Treat essential oils as concentrated products rather than stronger versions of the herb, and check with a pharmacist or doctor before using herbal preparations, particularly in pregnancy, while breastfeeding, or alongside medication. The full safety notice sits at the top of the Herb & Plant Guide.
Where to go next
Rather than repeating it here, the Plus Herb & Plant Guide holds the individual entries: magical associations, where the folklore actually comes from, practical uses and the cautions that matter for each plant.