The empress tree, also known as the princess tree, royal paulownia and paulowia tomentosa, is native to China but has naturalized throughout the eastern United States. This tree can grow up to 10 feet per year and is considered invasive in some states. This hardwood tree produces large leaves, making a great tree for shade. Depending on the cultivar, empress trees can grow up to 60 feet in height.
Most cultivars will grow anywhere on the East Coast, even up as far as Montreal. Before purchasing seeds, be sure you are getting seeds from a cultivar that will grow in your zone. If you are collecting seeds from an existing plant, allow the seed pods to dry on the tree. Harvest the seed pods and break them open to get the seed.
Be aware that this tree is considered invasive in most parts of the United States. It is banned in Connecticut. Empress trees will grow quickly along roadsides and in urban areas, potentially choking out native plant and tree species.
Planting Empress Tree Seeds
Light germination is the only thing needed to start empress tree seeds. This involves exposing the seeds to sunlight and moisture until they sprout. Before planting the seedlings, do a soil test to check the pH. The empress tree will grow in most soils, but it will do best in soil with a pH of 5.5 to 6.0.
The planting hole should be just deep enough to cover the seed. Place seeds at least 20 feet apart, as the canopy of the full-grown tree can be quite wide. Cover the seeds with soil (no more than ¼ inch), pat the soil down and water the seed. Make sure the seed has shade. During germination and growth, keep the seed bed moist-at least until the empress tree becomes established.
Encouraging Healthy Growth
Create a watering ring around the outside of the tree. The watering ring can be leveled out after a couple of years. The watering ring will ensure that the outside roots receive plenty of water, which creates a healthier root system and a healthier tree. Mulch the seed with compost. After the seedling grows to a couple of feet, you can mulch with compost or pulverized bark.
When the tree gets to be about two feet in height, stake it so that it doesn't get ripped out by high winds. Be sure to use a material that is easily removed, as empress is a fast grower, and the stake lines will need to be lengthened from time to time as the trunk gets thicker.
If you are not ready to use the seeds immediately after harvesting, store them in the refrigerator, separate from fruits and vegetables. Seeds can be stored in the refrigerator for up to a year.
In ideal conditions, a willow hybrid can grow 20 feet a year, although most of these trees average six feet of growth.
With its broad leaves and impressive size, Tulip Poplar is a great choice for a shade tree in your yard.