Goals, Trees and Balance
The desire to reduce the impact of climate change by planting one additional tree per person (100KTrees) may create conflict with other goals. Given the need for urban shade, water management, and reduction in air pollutants, it is easy to fall into trap of seeking the trees that grow the fastest in your area. This can directly challenge the desire to restore the local ecosystem, using native plants that generally are slower growing.
The overarching goal for the urban tree planting is to make the city a healthier for people to live. Tall trees grow canopy that cools the streets and offsets asphalt streets and buildings that push cities into becoming heat deserts. Rapidly growing trees will produce faster results to offset heat waves, which in 2022 arrived in many places which hadn’t experienced them in the past.
Native plants should be ideal, but they have self-selected over time for the historic weather patterns and the soil conditions. They may not be ideal for hotter and dryer (in the West) or wetter (in the East) climates. Additionally, many native trees grow more slowly than the newcomers. Species from outside the area may better address the human sense of urgency around mitigating climate change, which pushes us towards tree planting.
Urban trees need to be of sufficient size and vigor to survive the replanting and to thrive in what often is a more challenging environment than the nursery where they have spent the prior year or more. In simple terms, urban trees need a diameter of 2” to 3” to have sufficient strength to continue to grow into urban tree canopy.
I have been chewing on these ideas for a while: rapid growth vs. biodiversity, shortage of trees vs. restoration of native flora, impact vs. preservation.
Then I was introduced to World Tree USA. A brilliant approach — farm fast growing hardwood trees for carbon sequestration! Use them for furniture! After all, 30% of the world’s trees are on the edge of extinction! The Eco-Tree program has notable goals, success in the Southeast and the backing of Jimmy Carter. Sounds great, right?
Maybe.
World Tree’s focus is the Chinese Empress Tree, one of the fastest growing trees in the world. Also known as the Princess or Foxglove tree, the Paulownia family has 17 species. Originally from Asia (native of China, Laos, Vietnam and widely cultivated in Japan and Korea), the Empress Tree has broad leaves, beautiful purple, fragrant flowers and can grow 10 to 20 feet in height the first year. It grows best in poor soil and is known to increase nitrogen levels of the soil. The wood is blond and won’t warp, so it is ideal for furniture, windowsills, and other lumber uses.
Again, this sounds great, right?
Not so fast. Empress Trees are not one of the species at risk of going extinct. Just the opposite — it is growing in many places.
This tree’s rapid growth has made it a very invasive species. Empress Trees are classified as a noxious weed in Connecticut, where sales of this species are banned. In the US, the trees are most concentrated along the East Coast, and the south including Tennessee, Virginia, Florida and Texas. Empress trees have escaped gardens in 30 states and throughout Europe. This tree is known for squeezing out native ecosystems. The rapid growth of the Princess Tree (the Japanese name) allows it to outcompete native plants for water and nutrients. Those 8" to 16" leaves create significant leaf litter which can kill grasses.
Just one tree can take over an entire garden in a few years. After the first year, the trees continue to grow 10 to 15 feet annually until they are over 90 feet fall. Empress Trees produce thick, large roots that can damage asphalt, concrete and a building’s foundation.
Once planted, the tree is hard to get rid of. The roots are strong and spread just as quickly as the tree grows above ground. If even a tiny portion of the roots break off and remain in the ground when you try to remove this tree, it can start growing again. A large, established tree is almost impossible to remove because its roots can grow outwards up to three times as wide as the tree is tall. Additionally, each tree can drop up to 20 million seeds. Better Homes & Gardens describes the Empress Tree as a botanical nightmare.
Ecosystem Gardening says, Good Intentions Can Have Disastrous Consequences.
In defense of World Tree, they have focused on growing the 2 least invasive of the 17 species in the Paulownia family of trees. They are growing Empress Trees on farms and harvesting lumber. The flowers have a vanilla smell and have significant nectar. This seems likely to benefit a variety of insects.
Since the seeds are vulnerable to many of the soil microbes that make healthy soil, and young Empress Trees seem to grow best on soil damaged by fire or other means, I look forward to learning if, after harvest, the roots can be used to grow mushrooms for food or accelerate native soil microbes.
The best discussion of the pros and cons of Paulownia trees is this video. Great information, however, it has NO PICTURES of the Princess Tree throughout. Lots of flowers and plants, but not a single one from the tree it is discussing.
Balance and harmony: Nothing is entirely good or bad. Our goal is to reduce the impact of climate change as quickly as possible, and this means thoughtful solutions. An Empress Tree may well be a solution for a well maintained and managed park or farm.
Why does SymSoil care? We focus on solutions to environmental issues, with a focus on soil biology. Trees and plants feed, and are fed by, the soil microbiome. Healthy soil influences water, carbon sequestration and human health. SymSoil holds a patent on the first scalable approach to manufacturing Soil Food Web products as an alternative to agrochemicals.
SymSoil is a supporter of 100KTrees4Humanity, an urban tree planting project focused on action that moves us towards solutions to climate change with equity and inclusion.
