You will find details regarding bloom times below, green leaves start sprouting throughout April depending on the weather.
Source: The North Carolina Arboretum
When do the Azaleas bloom? In the Asheville area, our native azaleas begin blooming around the middle to the end of April. The exact bloom time will vary from year to year.
When do the Rhododendron bloom? In the Asheville area our Rhododendron usually bloom around the end of June. The majority of the plants that are on our property are Rhododendron maximum, Rosebay Rhododendron. This plant is also known by the common name "Laurel", but should not be confused with Kalmia, Mountain Laurel (Lance, R. Woody Plants of the Blue Ridge).
When do the Mountain Laurels bloom? A close relative of Rhododendron, laurel is sometimes called ivy and Rhododendron called laurel. The term "Laurel Hells" can refer to Rhododendron thickets which, with their dense, intertwined stems make cross country travel very tedious. Mountain Laurel blooms at the end of May.
What is that pretty pink/purple blooming tree I am seeing on the interstate? Well, you know the old saying "it depends"? In this case, that question depends on when you are traveling the highways. Redbud, Cercis canadensis, blooms in late March to early April and is one of our first native blooming trees of the season.
If you are visiting our area in later in the spring, late April to early May, the purplish blooming tree you are seeing is Princess-Tree, Paulownia tomentosa. Unlike the Redbud, Princess Tree is not native to this area, although it is still colorful. This tree blooms around the end of May.
Princess-Tree can quickly grow to as much as 60 feet and is not at all demanding as to moisture or soil. That's why we typically see it in locations where the soil has been disturbed and little else is growing.
Paulownia flowers are borne on erect panicles that grow upward. Each of those flowers produces a capsule that contains literally dozens of light, winged seeds that are widely disbursed by the wind. That explains how they reach high on the cliffs in the rocky gorge of I-40 west toward Tennessee, for example.
The flowers of the other possibility hang downward in showy clusters and that's an oriental Wisteria, Wisteria sinensis. This is a vine but when it climbs and envelops a tree it can easily be confused with Paulownia, being about the same shade of violet or purple.
Your answer then is to check the arrangement of the flowers. Growing upward equals Paulownia, hanging down, Wisteria. Paulownia, by the way, is the "Miracle Tree" you see advertised for its flowering beauty, rapid growth and tough constitution. But both Paulownia tomentosa and Wisteria sinensis are listed by several states and the US Forest Service as being invasive, definitely not the kind of plants you want to bring home to meet the family.