Lasiandra Tibouchina lepidota Alstonville (Pleroma)

Alstonville is the deep violet purple lasiandra, an upright large shrub or small tree with a rounded head that disappears under flower in autumn. The leaves carry the family signature, velvety and strongly ribbed, and the flowers open in a mass rather than a trickle. It was selected on the New South Wales north coast and it behaves like a warm climate plant. Gardens use it as an autumn feature and as informal screening, where one loud season is the point of the plant.

Acid soil, shelter, and no frost

It takes full sun to part shade with moderate water, and it grows at a moderate to fast rate in frost free coastal and subtropical gardens. Soil should be acidic, free draining and mulched; on alkaline ground the leaves yellow between the veins and the plant never really settles. In cold inland districts it burns back over winter and spends the following season recovering instead of flowering. Give it a sheltered position out of the strongest wind, and keep the spent flowers in mind, because they fall in quantity, which looks charming on lawn and much less so over a pool or light pavers. It grows well in a large pot if the mix is acidic and free draining, which is the practical answer in a garden built on limestone influenced soil. Plant it where the autumn flower is seen from indoors, since the season is short.

The failure mode is brittleness. The wood breaks easily, and a large plant allowed to get top heavy in an exposed spot will shed limbs in the first serious summer storm. Shelter plus regular hard pruning is the answer, not staking.

Alstonville or Peace Baby

The two lasiandras here come down to a straight choice between size and colour. Alstonville is the larger, more tree like plant with the deep violet purple flower, and it needs the room and the annual prune that go with it. Peace Baby is white flowered and naturally compact and rounded, which suits a small courtyard, a narrow bed or a large pot without much intervention. Pick Alstonville for mass and a screening role, and Peace Baby for a tidy plant in a tight space. Both want the same acid soil and the same shelter, so the site itself decides very little here; the space and the colour do. For a true flowering tree instead, look at golden trumpet tree. More in flowering.

Prune hard, and prune on time

Prune as soon as flowering finishes, and prune harder than feels comfortable. Cutting back by around a third keeps the plant furnished with foliage low down instead of drawing itself up into bare legs with a mop on top, and it builds the wood that carries next autumn's flower. Late pruning removes that flower, so timing matters more than technique here. A light tip prune in late spring holds the shape, provided you stop well before autumn. Feed after pruning with a fertiliser for acid loving plants, and add epsom salts if older leaves are yellowing between green veins, which is the magnesium shortage this genus is prone to.

Choosing a size

This plant is available in 3 sizes, from 180mm up to 45L, priced from $22.95 to $249.00 per plant. The size shown is the pot the plant arrives in, which is the rootball, not the height of the plant. The smaller pots hold younger plants that cost less each and establish quickly, which suits hedges, screens and mass planting where the plant count adds up. The larger sizes carry several more years of growth on the farm and give height and presence straight away, which is what you want for a single feature position or a screen that cannot wait. Not sure which to choose? Read our guide to choosing a tree for a small backyard.