More concise:
* "Purple blueberries are actually hybrids of Pacific blackberries and..."
* "The purple blueberry is a crossbreed of Pacific blackberry and..."
* "These purple blueberries are actually the result of crossing Pacific blackberries with..."
More descriptive:
* "The intriguing purple blueberry is not a true blueberry, but rather a hybrid created by combining Pacific blackberry with..."
* "While appearing like a blueberry, this purple fruit is actually a fascinating cross between a Pacific blackberry and..."
* "This vibrant purple fruit, often mistaken for a blueberry, is actually the outcome of breeding Pacific blackberries with..."
Formal:
* "The purple blueberry is a cultivated cultivar, derived from a cross between Pacific blackberry and..."
* "The botanical name for the purple blueberry reflects its hybrid origin, being a cross between Pacific blackberry and..."
Please note: To provide the most accurate and complete alternative phrasing, I need to know what the second parent plant is. For example:
* "Purple blueberry actually a cross between Pacific blackberry and raspberry"
* "Purple blueberry actually a cross between Pacific blackberry and highbush blueberry"
Once you provide the missing information, I can give you even more tailored options!