A native of Brazil, the princess flower (Tibouchina urvilleana) is a glorious addition to tropical and sub-tropical gardens. Its large purple flowers and soft hairy leaves add interest and a burst of color to any landscape. It can also be used as an indoor container plant in cooler regions if full light and warmth are provided. Though it is usually a shrub in the United States, it sometimes becomes large enough to form a small ornamental tree.
This shrub is a recipient of the Award of Garden Merit given out by the Royal Horticultural Society.
|Botanical Name||Tibouchina urvilleana. Sometimes it is listed as Tibouchina semidecandra. It is included in the Melastomataceae family.|
|Common Names||Princess flower, glory bush, pleroma, purple glory bush, or lasiandra. Princess flower may also be used for other species in the genus.|
|Plant Type||Perennial evergreen shrub or small tree|
|Mature Size||10 to 20 feet outdoors (can be pruned to be compact), two to three feet indoors.|
|Sun Exposure||Full sun, though it can tolerate some afternoon shade, especially in the hottest zones.|
|Soil Type||Rich, well-drained, acidic|
|Soil pH||7.0 or below|
|Hardiness Zones||Zones 9 to 11 are best for this shrub. It can be grown in Zone 8, but winter frost will cause it to die back until warmer temperatures return.|
How to Grow Princess Flower
Be sure to protect this plant against frost and strong winds. If you live in a cooler USDA zone, you could plant the princess flower in a container to be brought in each winter. You can also have it be a houseplant with enough warmth and light. You can propagate princess flower using softwood cuttings.
The princess flower is tall at its mature size and can be pruned to be more compact. It is round or vase-shaped. The leaves are two to six inches in length and one to 1 1/2 inches wide, covered in soft hair and often tipped with red around the edges.
The flowers are three to five inches wide and a deep, vibrant purple. Princess flower can produce blooms year-round, especially if it is deadheaded to encourage the formation of more flower buds. The fruit is a small brown capsule that is under half an inch long.
Use the princess flower as a specimen plant or for borders and foundations. The large vibrant purple flowers and soft hairy leaves work well in sensory gardens.
The princess flower prefers full sun but can tolerate partial shade if it receives at least five hours a day of direct sunlight. In fact, if you are in a particularly hot area, it's a good idea to provide some shade.
Your princess flower will appreciate damp, rich soil. While the plant does need regular watering, it's important that the soil drains well: princess flower can experience root rot if the soil is soggy.
Princess flower is somewhat drought tolerant but does best when regularly watered. Unless it's very hot, weekly watering is sufficient. Be careful to avoid overwatering, as very wet soil can injure the plant.
Temperature and Humidity
Princess flower cannot tolerate a real frost and will die back once a frost hits. If you want to keep your plant from dying back you can bring it indoors for the winter. One option is to cut the plant back to about eight inches and keep it in the garage or basement. If you do keep the plant in the dark, water it only enough to keep it from drying out.
It's best to fertilize your princess flower each spring, summer, and fall. You can use fertilizer intended for acid-loving plants such as rhododendron or azalea, but your plant will also appreciate a bit of manure. Mulching will help your princess flower to retain moisture.
Prune the princess flower to maintain a rounded shape. Pinch new growth to encourage branch formation. Prune lightly after blooming. This shrub can be trained to form a standard if you prefer it to have a tree shape.
You can clip any dead branches at any time. This may be necessary if the plant is near a walking path, or if the branches are too low to the ground.
Common Pests and Diseases
Occasionally scale, nematodes, aphids, mealybugs, and geranium budworm may attack the princess flower. To manage these, you can introduce beneficial insects such as ladybugs, or clean your plant using insecticidal soap or horticultural oil.
Mushroom root-rot can occur if princess plant is kept in soggy soil. To avoid this problem, water no more than once a week and check to be sure that your plant is not receiving too much rain.