Thinning out seedlings in the garden is important for crops...but why?
Thinning out seedlings to allow enough space for the remaining plants to grow is an important part of growing many crops. Lettuce is a good example, along with spinach, chard, carrots and beets.
Spittle bug is a grotesque little creature that makes a foamy home that looks just like spit. Some plants have little or no response while others become a little deformed. A blast of water to the spit blob and the problem is solved.
Grape clusters should be thinned to allow only two per cane so that each can attain a better size. Many other advantages of thinning include earlier harvest and better cold hardiness.
You can head to the Milwaukee County UW-Extension Horticulture page for more gardening information.