Every player of Fairyland on Facebook has a Wilt Balance, shown near the bottom of the right-hand column of the garden. Wilting is a way of penalising players whose plants are not watered in time (which varies among different plants, some lasting 48 hours, others lasting less than 14).
Your Wilt Balance is a whole number, positive or negative or zero, calculated over the past 7 days. Every plant of yours that starts wilting counts as "-1" against your balance. To keep your balance positive, you may spend 2 gold or a diamond to revive a wilter in someone else's garden for a "+1" to your balance.
Plants that reach their limit start wilting, stop growing, cease having any effect on Wildlife, and cost more to water for the revival. (If still left unwatered, they eventually die and cost much more to revive.)
If your balance is below +1, you do not lose growing plants but you are prevented from sowing as many new seeds as you have room for and from refilling the feeding table if it makes up the maximum number of used containers. (Until early April 2009 the limit was +5.)
Restoring your balance
Looking for other players' wilters is easy. Click the "All Gardens" tab, which displays your friends' gardens on the left, your favourite gardens in the middle, and a random selection of public gardens on the right, each column arranged in order of thirstiness with any wilter gardens at the top. Gardens with wilters have a brown circle showing "3" (which means their health is at grade 3 because they have at least one wilter). Click on one of those to visit it. There is a separate link that shows more public gardens, those that have had a wilter for 4 hours or more.
Improve your chances of finding a wilter
If you go for the public lists you may find others have beaten you to any particular garden. To improve your chances of finding a wilter, make gardens that seem to be "persistent wilters" your favourites. They will then show near the top of the middle column as soon as any plant wilts, which gives you a 4-hour start on the "public".