Sindar of Doriath

Nightingales Generally ascribed meanings: the Queen Melian, song, love and devotion, bonding, joy

Bracken fern and fiddleheads fern Generally ascribed meanings: geometry and order

Beech Leaves: Generally ascribed meanings: Abundance, generosity, resourcefulness

Holly leaves Generally Ascribed Meanings: honor, defense, resilience

Oak leaves Generally ascribed meanings: Friendship, loyalty

Niphradel and snowdrops Generally ascribed meanings: purity, youth, innocence, cycles

Elanor Generally ascribed meanings: light, growth, curiosity

Bluebells Generally ascribed meanings: spring, fleet footedness

Elm leaves Generally ascribed meanings: the king, service, steadfastness

Sindar of Mithrim

Nettles, stem, leaves and flowers Generally ascribed meanings: nettles are used in the northern Sindar culture in a variety of ways including fiber for fabric, eating, and medicinal teas. Their appearing in heraldry, art and symbolism is usually believed to mean resilience, the change of winters to spring, and the earths resources

Clouds Generally ascribed meanings: the heavens, tranquility

Outline of mountains Generally ascribed meanings: history, family, honesty

Wolf's Bane Generally ascribed meanings: Lore, knowledge

Blue bellflower: Generally ascribed meanings: color, joy, exploration

Trout Generally ascribed meanings: home, water

Lake birds (herons, swans) Generally ascribed meanings: grace, flight, legacy

Lake birds (ducks, loons, teals) Generally ascribed meanings: cycles of life and predation, respect for land

Fir tree Generally ascribed meanings: shadow and light, truth

Sunflowers Generally ascribed meanings: joy, sun, day

Sindar of Nevrast (non Falathrim) Aquatic birds one (ducks/shelducks/grebe/teals/eider/sea ducks) Generally Ascribed meanings: stability, peace, family

Aquatic birds two (cranes/egrets/herons) Generally ascribed meanings: grace, skill, aptitude, seeking

Aquatic birds three (loons, crakes, rails, etc) Generally ascribed meanings: song, mystery, change

Ripples on a lake Generally ascribed meanings: the world, the ages, time

The clifflines of Nevrast: Generally ascribed meanings: strength, wisdom

Marsh grasses: Generally ascribed meanings: roots, abundance

Sea Lavender Generally ascribed meanings: the lands and sea, gentleness

Sunflower or daisy

Generally ascribed meanings: resilience, loyalty

General among the Sindar of Beleriand:

hummingbirds generally ascribed meanings: pollination, flora and fauna, wonder

butterflies and dragonflies generally ascribed meanings: change and transformation, fragility and beauty

willow trees generally ascribed meanings: peace, connection to Ulmo, mystery, prophecy

Obviously this isn't a complete list as many, many species of flora and fauna have their own meanings! Please feel free to ask about any or ask any world building questions! I hope this is ok!