I don't know how much space you're allowed, but this is what i'd do:
- Use the word ORCHID somewhere prominently
- Use strong, contrasting colours
- Use a picture of an orchid that is recognisable to the casual windowsill grower - An Epicat might not be recognisable as an orchid by most of the target market.
- If it's for an auction, include the date so people know the ad is current.
- Use a location somewhere so people know that it's local.
- Use the word free somewhere
- NOT use the word 'society' somewhere, that sounds exclusive and unwelcoming, even if it's not.
P.S. I voted for the breasts standing next to the tree (oh there was an orchid?)