- Name: Royal Paulownia Empress Tree - Scientific Name: Paulownia Tomentosa - Color: Light Purple - Plant Seeds: Outdoors After Frost / Indoors Weeks Before Last Frost - Bloom Time: Spring - Hardiness Zone: 5 - 9 - Plant Height: 40 Feet - Plant Spacing: 20 Feet - Light Requirements: Sun - Part Shade - Soil & Water Preferences: Average - Quantity: 400 Seeds - Other: The Empress Tree Is One Of The Fastest Growing Trees Around! It Grows An Average Of 10 Feet A Year, And 15 Feet Of Growth In A Year Is Not All That Uncommon. It Makes A Great Shade Tree, And Is Unbelievably Beautiful In Spring Drenched In Big Gorgeous Many Hued Blooms.