What is that tree blooming on the side of the highway? The one with light purple flowers that look like Wisteria, except the panicle points up rather than hanging down.
This is Paulownia tomentosa, often seen in cheap looking ads from mail order nurseries called the Empress tree or Princess tree. The ads tout its rapid growth and long lasting blooms, and grow it does, often nearly ten feet per year. The flowers last a couple weeks at most, but are quite attractive.
The wood of Paulownia is prized in Japan for use in making furniture, and there are tree farms in the southeast that have tried to promote similar commerce in the United States with limited success. Trees escaped from cultivation years ago, and are on many invasive plant lists since a large tree can produce well over a million seeds, and the seeds will germinate in poor soil in just about any sunny location.
Why not plant one in your garden? I did.
Years ago I snatched a waist-high seedling from the gravel shoulder of a nearby highway. “Grab and pull” is not the recommended method of transplanting most trees, but Paulownia withstood this abuse easily, and grew in my garden without a pause. I recognized long before invasive plant lists were established that trees flourishing on roadsides were likely to be problematic, and intended to grow mine for its leaves only.
I’ve been an addict to plants with huge leaves forever, and my garden is filled with hostas, a Bigleaf magnolia, tropical elephant ears and bananas, and anything else I can find with leaves a foot or more across. I’ve tried Gunnera, which can have leaves more than six feet across, but haven’t latched on to the secret for getting it through our Winters.
Anyway, if Paulownia is cut back several times each year it won’t bloom, and thus no seeds, but the enormous energy from the tree goes into growing leaves two feet across. I tried to maintain my Paulownia at about seven feet, a height I could comfortably reach to prune, but within days of chopping it back it would spurt skyward again.
I loved the huge leaves, but after a couple years I realized that I would eventually lose this battle, and chopped it out. For another year I fought suckers from the roots, but finally was rid of this beast.
Should you plant one? There are more idiotic things you could do, like plant a wisteria and fight a losing battle with it for another decade or two, or plant bamboo and decide that selling the house and moving is easier than getting rid of it. I’ve planted those too. But, generally I believe it’s best to avoid plants that are intent on conquering the planet.