When doing rituals or workings to honor Gods, you may want to invoke the energy of a certain God or ask Him to join you. Scent is very pleasing to the Gods. Here is a quick reference for your Book of Shadows for Gods.

Adonis: myrrh, corn, rose, fennel, lettuce, white heather
Aesculapius: bay, mustard
Ajax: delphinium
Anu: tamarisk
Apollo: leek, hyacinth, heliotrope, cornel, bay, frankincense, date palm, cypress
Attis: pine, almond
Ares: buttercup
Bacchus: grape, ivy, fig, beech, tamarisk
Baldur: St. John's wort, daisy
Bran: alder, all grains
Cupid: cypress, sugar, white violet, red rose
Dagda: oak
Dianus: fig
Dionysus: fig, apple, ivy, grape, pine, con, pomegranate, toadstools, mushrooms, fennel, all wild and cultivated trees
Dis: cypress
Ea: cedar
Eros: red rose
Gwydion: ash
Helios: sunflower, heliotrope
Herne: oak
Horus: horehound, lotus, persea
Hypnos: poppy
Jove: pine, cassia, houseleek, carnation, cypress
Jupiter: aloe, agrimony, sage, oak, mullein, acorn, beech, cypress, houseleek, date palm, violet, gorse, ox-eye daisy, vervain
Kernunnos: cinnamon, mulberry, hazel, willow
Kanaloa: banana
Mars: ash, aloe, dogwood, buttercup, witch grass, vervain
Mercury: cinnamon, mulberry, hazel, willow
Mithras: cypress, violet
Neptune: ash, bladderwrack, all seaweeds
Odin: mistletoe, elm
Osiris: acacia, grape, ivy, tamarisk, cedar, clover, date palm, all grains
Pan: fig, pine, reed, oak, gern, all meadow flowers
Pluto: cypress, mint, pomegranate
Poseidon: pine, ash, fig, bladderwrack, all seaweeds
Prometheus: fennel
Ra: acacia, frankencense, myrrh, olive
Saturn: fig, blackberry
Sylvanus: pine
Tammuz: wheat, pomegranate, all grains
Thoth: almond
Thor: thistle, houseleek, vervain, hazel, ash, birch, rowan, oak, pomegranate, burdock, beech
Woden: ash
Zeus: oak, olive, pine, aloe, parsley, sage, wheat, fig