Wave petunias (Petunia x hybrida "Wave") are prized for their brilliant masses of colorful blooms. Hardy in U.S. Department of Agriculture plant hardiness zones 10 through 11 and grown as annuals elsewhere, these trailing and spreading plants look equally attractive when grown in containers or as bedding plants. With proper care, Wave petunias bloom profusely; so the best thing to do if they are not blooming is to make sure your petunias are getting everything they need to thrive.
Sun and Light
All petunias need full sunlight to bloom properly, and this is especially true of Wave petunias, which have blooms that line their long stems rather than just clustering at the tip. Watch your flowers throughout the day -- if they are in the shade for more than an hour or two, consider moving them to a location where they'll be in the sun all day long.
Soil and Water
Because they like the sun, Wave petunias need a lot of water. What they don't need is a little bit of water sprayed on them occasionally. The flowers don't like to be wet -- they tatter easily in the rain -- and constantly wet foliage can lead to fungal diseases that can prevent them from blooming. Instead, give your Wave petunias a slow, deep watering at the ground level. Give them about 2 inches of water once a week, or enough to keep the soil just barely moist to the touch. Too much water, on the other hand, can lead to root rot, so make sure your petunias are not located in a depression where water can collect. If they are in a container, make sure it has holes and that the water can drain freely out the bottom.
Wave petunias don't usually become leggy, because of the way they spread, so they don't necessarily need to be cut back. On the other hand, cutting them back after the first flush of blooms can stimulate them to bloom again later in the summer, according to the Missouri Botanical Garden. If your flowers bloomed once but are no longer blooming, try cutting them back by half their length.
Deadheading and Fertilizing
Deadheading means to remove the spent blooms from the plant. This directs the plant's energy into creating new blooms rather than producing seeds. Wave petunias are often deadheaded before they are sold, but they also need to be deadheaded on a continuing basis once in your garden. Fertilizing also helps your plant create more blooms. Use a water-soluble, balanced fertilizer designed for flowering annuals, and follow the directions for application on the package.
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