Answer: To pinch the cascading petunias, simply trim off the growing tip using scissors or your fingernails. This should force the plant to branch.
Petunias are grown as annuals in our cold weather climates, so you will need to replant them each year. They bloom beginning at a fairly small size/young age and will continue blooming until frost. Remove the spent flowers to prevent seeds from forming, and to encourage the plant to bloom more. (This is referred to as deadheading.) This process does not involve cutting the plant back and doesn't affect bushiness.
The waves tend to be more self branching and grow naturally denser and thicker than the cascades. One of the characteristics of the cascades is lenthy branches so they will trail over a hanging basket or the edges of a planter like a waterfall or cascade.
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