Flowers are great to use when there is a lot of emotion involved, especially love, naturally. They are moderately easy to use, and most are available at any flower shop. The more flowers you have, the more effective the spell will be.
Acacia - friendship
Amaryllis - Beauty, timidity, shyness, love
Anemone - Abandonment, forsakeness
Apple Blossom - Preference
Arbutus - Fidelity, true love
Aster - Variety
Bachelor's Button - Hope, patience
Beech (Fire Element) - Personal finances, gambling, money
Birch - (Water Element) - Dreams, astral travel
Buttercup - (Fire Element) - Ambition, social matters, riches
Camellia - Gratitude
Red Carnation - Poor Heart, forlorn
Pink Carnation - Deep Love
Striped Carnation - Refusal
White Carnation - Purity
Cedar - (Fire Element) - Goals
Cherry - (Earth Element) - Intelligence
China Aster - Variety
Red Chrysanthemum - Love
White Chrysanthemum - Truth
Cinnamon - (Fire and Water Elements) - Business, logic
Clematis - (Earth and Air Elements) - Soulmates
Cock's Comb - (Fire and Water Elements) - Partnerships
Coltsfoot - (Fire and Water Elements) - Political Power
Cyclamen - Diffidence
Daisy - (Fire and Water Elements) - Swift movement, a decision
Dahlia - Dignity and elegance, or instability
Daffodil - Unrequited love, or high regards
Fern - (Earth Element) - Wisdom, fascination
Fir - (All Elements) - Manifestation
Forget-Me-Not - Remembering, clinging to the past
Fuscia - Taste or frugality
Geranium - Preference, Friendship
Gladiolus - Strong character, strength, integrity
Hazel - (Earth Element) - Communication
Heather - (Earth and Air Elements) - Beauty
Hemlock - (All Elements) - Protection
Heliotrope - (Fire Element) - Success
Hibiscus - Delicacy, beauty, fragility, temporary pleasures
Holly - Questioning
Hyacinth - Constancy
Iris - (Water Element) - Reincarnation, a message, travel
Ivy - (Earth and Air Elements) - Friendships
Jonquil - Desire
Lavender - (Earth Element) - Healing, faith
Purple Lilac - First emotions of love, obsession
White Lilac - Youth, children
Lily of the Valley - Happiness, good luck
Marigold - (Fire Element) - Health, affection, or constructive loss, rebirth
Morning Glory - Affection
Moss - (All Elements) - Binding
Motherwort - (Water Element) - Imagination, creativity
Myrrh - (All elements) - Binding
Narcissus - Egotism, self love, self concept
Nasturtium - Patriotism, paternal love
Nightshade - (All Elements) - Death, rebirth, lunar activity
Oak - (Fire Element) - Personal finances, wealth
Orris Root - (Water Element) - Psychology, subconsciousness, psychicism
Pansy - Thoughts, reflection, memory
Peony - Shame, bashfulness, unrealized desires
Pepper - (Fire and Water Elements) - Energy
Periwinkle - (Earth Element) - Memory, Education
Pine - (Fire and Water Elements) - Courage
Poppy - Consolation, avoidance of problems
Pink Rose - (Earth and Air Elements) - Romantic love
Red Rose - (Fire and Water Elements) - Passion
White Rose - (Water Element) - Silence
Wild Rose - (Earth Element) - Simplicity, honesty
Yellow Rose - Unfaithfulness
Sage - (Earth and Air Elements) - Artistic ability
Sweet Pea - A meeting
Sweet William - Gallantry
Thyme - (Fire and Water Elements) - Swift movement, action
Tulip - Fame
Vervain - (Water Element) - Feminine power, women's power, abilities, problems
Violet - (Earth and Air Elements) - Artistic ability, faithfulness, fidelity
Water Lily - (Earth and Air Elements) - Harmony
Willow - (Water Element) - Psychology, psychic powers, psychicism
Wolfsbane - (All Elements) - Neutralization, balance, temperance
Zinnia - Absence, lost friends