Shrub
Princess flower
Pleroma urvilleanum · Melastomataceae
Also called: Glory bush, Tibouchina, Purple glory tree, Lasiandra
Princess flower (Pleroma urvilleanum) is a high-water shrub well suited to Tucson and the low desert. It thrives in full sun to part shade, with a moderate to fast growth rate.
Princess flower at a glance
- Water use
- High (established)
- Sun
- Full sun to part shade; in Tucson provide morning sun with afternoon/filtered shade to prevent leaf scorch and stress in summer.
- Mature size
- Commonly kept 4-8 ft tall and wide in cultivation; can reach 10-15+ ft in frost-free, ideal climates
- Growth rate
- Moderate to fast
- Bloom
- Brilliant royal-purple/violet flowers up to ~3-4 in across, Warm months, heaviest in summer and fall
- Cold hardiness
- Frost-tender; foliage damaged below ~32 F and plants die back or are killed in hard freezes. Best in a warm, protected microclimate or as a container plant with winter frost protection in USDA 9a-9b.
- Soil
- Needs rich, acidic (pH ~5-6), well-draining soil with organic matter. Poorly suited to native caliche/alkaline soils; grow in heavily amended beds or large containers.
- Native range
- Brazil
- Best used as
- Tropical-look flowering accent, Container/patio specimen, Focal-point shrub in sheltered, irrigated gardens
- Wildlife
- Flowers attract bees and butterflies.
- Toxicity
- Not known to be significantly toxic; generally considered non-toxic to people and pets, but not intended for consumption.
How to grow Princess flower in Tucson & the low desert
Watering
Keep soil consistently moist; water 2-3 times per week in summer heat. It is not drought-tolerant and wilts quickly when dry; mulch heavily and protect from drying wind.
Fertilizer & nutrients
Prefers acidic conditions. Feed with an acid-loving-plant fertilizer in spring and early summer and supplement iron/micronutrients; Tucson's alkaline soil and water cause iron chlorosis (yellowing leaves with green veins).
Pruning & care
Prune to shape and encourage bushiness after the main bloom flush; pinch growing tips on young plants. Remove frost-damaged wood in late winter once freeze danger passes.
Notes
Spectacular purple bloomer but a high-input, marginal plant for the low desert: it dislikes heat, intense sun, alkaline soil/water, and frost. Reserve for sheltered, well-amended, acidified, regularly irrigated microclimates or grow in pots. The accepted botanical name is now Pleroma urvilleanum (formerly Tibouchina urvilleana).
Sources: University of Florida IFAS Extension (ENH791, Tibouchina urvilleana); Wikipedia/POWO nomenclature (Pleroma urvilleanum accepted name); University of Arizona Cooperative Extension (alkaline soil / chlorosis guidance)