Petunias are widely grown flowering annuals, valued for their trumpet-shaped blooms and ability to provide continuous color throughout the growing season. Their color palette offers a vast spectrum suitable for nearly any gardening design. This diversity includes solid colors, complex patterns, and striking bi-color combinations, developed by breeders manipulating the natural pigments.
The Solid Color Range
The most prevalent colors in petunias span the spectrum from bright whites to the deepest purples. Shades of pink and magenta are common, often presenting in soft pastels or vibrant, nearly fluorescent hues. Red varieties offer a range from classic scarlet to deep crimson, providing a traditional anchor for many garden displays.
The purple and blue range is extensive, though true, pure blue is a difficult shade to stabilize and often appears as a rich indigo or violet hue. White petunias serve as a bright counterpoint to darker colors. Yellows are also available, typically appearing as pale lemon or lime shades, since the plant’s chemistry does not naturally produce the deep golden tones seen in other flowers.
A more recent development is the near-black petunia, which is actually a highly concentrated, deep burgundy or mahogany purple. This sought-after color achieves its dark, velvety appearance from an intense accumulation of pigment. Petunias are notably absent in the true orange color, which is a rare shade often only achieved through advanced genetic techniques that borrow pigment pathways from other plant species.
Distinct Patterns and Bi-Color Varieties
Beyond the solid-colored blooms, many petunia varieties are known for their intricate, multi-toned patterns. One of the most common is veining, where a network of fine, dark lines contrasts sharply against a lighter base color, drawing attention to the flower’s throat. This effect is particularly prominent in purple and plum varieties that have a light pink or white background.
Another striking pattern is the picotee, which features a contrasting colored edge, or margin, around the entire rim of the petal. A classic example is a deep purple bloom with a perfectly uniform white border, creating a sophisticated, two-toned look. Bi-color varieties also include the star pattern, where a distinct, five-pointed star shape radiates outward from the flower’s center.
This star pattern is formed by a band of color that follows the midrib of each petal, often appearing as a white star on a purple or red background. Other complex patterns include contrasting throats, where the very center of the funnel-shaped bloom is a different color than the main petal face.
How Breeders Create Such Variety
The extensive color range is a result of the plant’s internal chemistry. The majority of petunia colors, including the pinks, reds, purples, and blues, are derived from a class of compounds called anthocyanins. Different chemical modifications to the anthocyanin molecules, such as the addition of sugar groups or changes in the cell’s acidity, result in different visible colors.
A shift in the pH level of the flower’s vacuole, the storage area for the pigment, can cause a color change; a more acidic environment tends to produce a redder hue, while a less acidic one leads to bluer colors. The yellow and pale orange colors are primarily attributed to carotenoids, a separate class of pigments also responsible for the colors of carrots and corn.
Modern breeding efforts rely on both traditional crossing methods and, in some cases, genetic manipulation. Breeders use cross-pollination between parent plants to create hybrid seeds that reliably produce a uniform color and growth habit. They stabilize new colors and patterns by selecting and propagating plants that express the desired traits, allowing for the continuous introduction of novel petunia varieties.