Growing Concerns: Royal empress tree reigns in Oak Harbor garden

I live in Oak Harbor and have a tree in my back yard I need to identify. It has lovely purple, trumpet-shaped flowers that bloom in April/May and are gone by June. The leaves at that time are just starting to come out. After the flowers are gone the leaves grow to 8-12 inches by 15-18 inches. The tree is about 40 feet tall with a 15-foot spread. It is at least 40 years old.

When we trimmed it years ago, we found the wood to be soft and hollow, or nearly so, in the center. One way it propagates is by sprouting lovely purple shoots from a surface root. In two to three years, the shoot will be a small tree about four feet tall with all the characteristics of the mature tree. The tree does develop a seed pod, but I have not tried to get it to germinate.

I’ve been asked at least a hundred times for the name of the tree, and have had to plead ignorance each time. Web searches have made me no smarter. I’ve attached three pictures of the tree in bloom, the flowers, and the starting leaves. Thank you for any help you can provide. – Ted.

Ted, you have royalty in your back yard. Paulownia tomentosa, otherwise known as the empress tree, or royal empress, is truly regal. In springtime, nothing can compare to its lavender blue clusters of fragrant, trumpet-shaped flowers. Summer brings a profusion of huge, heart-shaped leaves. It doesn’t have much fall color, but brown flower buds form in autumn and burst into bloom before leafout in May. The top-shaped seed capsules that follow the flowers were once used as packing material. When dried, the capsules contain a soft, fibrous material that before the advent of bubble wrap, was used to pad china being shipped from, well, China, where the tree originated.

Although classified as a hardwood, it’s the softest wood in this category. Said to be the fastest growing hardwood tree on earth, Paulownia has been used in Chinese medicine for centuries. In Japan, Paulownia is carved into bowls, chests, and other beautiful and useful items.

Environmentally, Paulownia may be useful in a number of ways. Because it grows so rapidly, it can be used for reforestation, even on ravaged land. According to the American Paulownia Society, the tree decreases soil salinity while increasing fertility. It also produces three to four times more oxygen than any other known tree, while removing carbon from the air.

Not everyone, however, loves the empress. In milder areas, it’s considered an invasive pest, due to its penchant for sprouting multiple offspring from surface roots. This doesn’t seem to be a major problem in the Pacific Northwest. It also has an extensive root system, which makes it a poor choice for planting anywhere near septic systems. The Sunset Western Garden Book says Paulownia is “Not a tree to garden under due to dense shade, surface roots.”

For those who have the space, Paulownia gives an exotic, almost tropical feel to a garden. We purchased three of them several years ago. They were 30-inch saplings when planted, and the following spring, they looked like 30-inch sticks. We cut one back to the ground to see if it would produce new growth, and ignored the other two. The one we cut back never recovered. However, after two years, the others have finally taken off. I’ve since learned that it sometimes takes two to three years for young Paulownia to show growth. After that, watch out! It can grow quickly to 50 feet tall with a nearly equal spread.

Once established, the empress isn’t fussy. It does best in deep, well-drained soil and should be protected from strong winds.

While not a common landscape tree, many an empress flourishes on Whidbey Island. You can see a 50-foot specimen at Meerkerk Rhododendron Gardens in Greenbank, where it blooms in concert with rhodies and early perennials.

Mariana Graham writes this biweekly column as a volunteer WSU-Island County Master Gardener. Contact her at

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