For an alphabetical listing of plants beginning with each letter of the alphabet, have a look at: http://en.wikipedia.org/wiki/List_of_garden_plants Thats one way of making wikianswers redundant.
sunflower
scilla
snowdrop
strawflower
snowflake
sollya
Sturt's Desert Pea
salvia
santolina
scaeveola
scabious
schizanthus
snapdragon
shasta daisy
spirea
stock
strelizia
Salvia, or sage
SUNFLOWER-stargazer lily
snapdragons
sour tree
Snapdragon, Soldaster and Sweet Pea are flowers. They begin with the letter S.
SalviaSabi StarSand_VerbenaSarraceniaSatin_PoppyScarlet_PlumeScorpion_SennaSea_LavenderShaddockShamrocksShasta_DaisySnap_DragonsSnow_DropSnow_FlowerSowbreadSpear_LilySpider_LilySpoon_LilySpurgeStar_of_the_VeldtSummer_HyacinthSunflowerSwamp_DaisySwamp_HibiscusSwamp_LilySweet_MarySweet_SultanSweet_WilliamSyringa
Sweet pea, sunflower, salvia, snowball and snapdragon are flowers. They begin with the letter S.
Salvia, snapdragon, snowball, soldaster, statice, stephanotis, sunflower and sweet pea are flowers.
Sweet Pea and Salvia are flowers. Soldaster is a flower.
Scabious can be white
Yes, the Sunflower.
snowball
sillyablesquashsweeny toddsprinkle hairspace macers
sabatia angularis
Here are some flowers that begin with the letter S:SafflowerSagittariaSaintpauliaSalixSalviaSanguinariaSansevieriaSantolinaSaponariaSarraceniaSaxifragaScabiosaScillaSea lavenderSedumShasta daisyShell flowersSnapdragonSnowballSoldasterSolidagoSolidasterSpider lilySpider mumsStachysStanhopeaStaticeStephanotisStreptocarpusSunflowerSweet peaSword fern
Some three letter words that start with S are: sadsagsapsatsawsaxsayseaseesetsewsexsheshysicsinsipsirsissitsixslyskisobsodsonsotsowsoyspystysubsumsunsup