Nine woods in the Cauldron go, burn them fast and burn them slow.

Birch in the fire goes to represent what the Lady knows.
Oak in the forest towers with might, in the fire it brings the God's insight.  
 Rowan is a tree of power causing life and magick to flower.
Willows at the waterside stand ready to help us to the Summerland.
Hawthorn is burned to purify and to draw faerie to your eye.
Hazel-the tree of wisdom and learning adds its strength to the bright fire burning.
White are the flowers of Apple tree that brings us fruits of fertility.
Grapes grow upon the vine giving us both joy and wine.
Fir does mark the evergreen to represent immortality seen.
 

Almond - Clairvoyance, divination, moon magick, wisdom

Alder - Balance, courage, Spirit

Apple - Healing, love, perpetual youth, prosperity, fertility

Ash - Protection

Apricot - Love

Aspen - Protection

Birch - Fertility, new beginnings, protection, purification, the Goddess. 

Cedar - Longevity, prosperity

Coconut - Chastity, healing, purity

Cypress - Past-life workings, protection

Elder - Healing, prosperity, protection

Elm - Protection

Eucalyptus - Healing

Fig - Fertility, healing, sensuality

Fir - Immortality

Grape - Joy

Hawthorn - Cleansing, love, protection, faeries

Hazel - Divination, protection, reconciliation, wisdom, strength

Holly - Protection, truth, love, sacrifice, re-birth

Juniper - Protection

Lemon - Chastity, divination, friendship, healing, wishing

Maple - Divination, love

Mulberry - Divination knowledge, will power, wisdom

Oak - Healing, finances, longevity, strength, the God

Olive - fidelity, fruitfulness, peace, security

Orange - Love, marriage

Palm - Strength

Peach - Divination, love

Pine - Fortune, fertility, health, prosperity, purification

Rowan - Protection, strength, magick

Walnut - divination healing, Oracle, protection

Willow - Enchantment, healing, moon magick, protection, the Underworld

Yew - Altered states of consciousness

Sources: 

Beltane by Raven Grimassi

The Wiccan Rede