However, certain herbs and scents are particularly associated with Aradia and Diana, including rue, vervain, verbena, lemon verbena, van-van, and sometimes fennel and lavendar.
So, what is the best way to offer herbs and scents, particularly associated with Aradia and Diana, to these two goddesses?
Vervain may be made into an infusion like rue. See Vervain Infusion. Vervain water can be used in bath waters and beauty spells. It is sometimes used to banish unwanted spirits and ghosts. Like rue water, it is also known as Juno's Brew and can be sprinkled on an altar with an offering candle. In ancient Roman times, vervain was strewn on altars as an offering.
Modern Wiccans often annoint, or dress a candle, for offerings with an essential oil that has been mixed with a base, like almond oil or extra light olive oil.
Essential oils, incidentally, are not true oils. They are volatile liquids that are extracted by a number of methods--usually steam distillation--from aeromatic botanicals. True oils, also known as base oils, or fixed oils, include olive oil and almond oil, which are extracted from the fruit or seeds of plants.
Apparently vervain is a botanical from which no essential oil is produced. Sometimes you can find stuff labeled verbena or vervain that is commercially made. Generally, this essential oil is lemon verbenna. Lemon verbena (Lippia citriodora), aka verbena, is similar to vervain (Verbena officinalis), magically speaking. However, the two plants are botanically unrelated. Lemon vervena is also sacred to Diana and Aradia, because of its lemony scent. According to Leland, lemons were sacred to Diana and her strega daughter, perhaps because of the fruit's yellow color.
If you wish to dress an offering candle to Aradia with genuine or "official" vervain (Verbena officinalis), you can dress the candle with the dry, powdered herb. Carve whatever marks, letters, words, or sigils into a pure beeswax candle with a special carving knife or a pin. Apply olive oil in the middle. Stroke up from the middle and then back down to the base. Roll the annointed candle in powdered vervain to complete "dressing the candle." (Dried, powdered rue can be used to dress a candle in the same way.) There is an old-fashioned way to make a homemade leaves and flowers vervain oil. See recipe: Leaf and Flower Vervain Oil.
Judika Illes, in The Element Encyclopedia of 5000 Spells, 2004 (p. 31-32), gave a recipe for oil-based infusions. This recipe involved using a bain marie (balnucum Marie) or more commonly known as a double boiler. See Oil-Based Infusions. This is another method for making vervain scented oil. I have run across one source that sells a floral-scented vervain oil: The Crystal Fox.
This ability to associate one idea with another metaphorically seems to be key to our specie's ability to think abstractly and even develop language.