The empress tree, or Paulownia tomentosa, is sometimes referred to as royal paulownia or princess tree. This plant loves warm weather, and is hardy only to the milder regions in USDA Planting Zone 5. Young specimens produce gargantuan leaves, but don’t worry because the mature tree eventually grows into them. Paulownia is easily propagated from seed. In fact, this plant seeds itself so freely that many people refer to it as a noxious, invasive weed. Germination is easy and growth is rapid, so be prepared to enjoy this beauty early on.
Fill the cells of a plastic seedling 6-pack to within ¼ inch of their tops with a good all-purpose potting soil in January. Set the pack in a shallow container of warm water until the soil surface feels moist to your touch. Remove it from the water and allow it to drain well for about 2 hours.
Press an empress seed into the surface of the soil of each cell in the pack. Don’t cover the seeds, as they require a great deal of light for successful germination. Set the seed pack in a very warm, brightly lit spot. The top of your refrigerator or above a hot water heater are good choices. The temperature must be from 70 to 85 degrees F.
Hang a 40-watt shop light over the seed pack and keep it lit until seeds germinate. Keep the soil evenly moist, but not soggy or wet. Your empress tree seeds will sprout in about 9 to 21 days.
Transplant the seedlings in individual 4-inch clay pots when they’re 1 or 2 inches tall. Use the same planting medium that you sprouted them in. Set them on a warm, bright windowsill and keep the soil evenly moist.
Move the empress tree seedlings outside to a shady spot after all danger of frost has passed for your area. Protect them from wind and rainfall for 10 to 14 days and keep the planting medium evenly moist. Thereafter they can be planted in full sun.