How to grow them
Climate Deciduous magnolias like a chilly, moist winter followed by a warm, moist summer. They thrive along the Great Dividing Range and in south-east Australia – anywhere rainfall is reasonably generous (or adequate irrigation is available) and where winters are cool enough to induce dormancy. They’re not for the tropics or the steamy sub-tropical coast.
Aspect Full sun is most suitable, but they’ll grow with a little shade and enjoy the shelter of other large shrubs or small trees. Strong winds will damage the flowers and break the brittle branches, so try to plant in protected areas.
Soil The most important feature of a suitable soil is that it holds moisture but not wetness. Average garden soil will suffice as long as it drains freely. Magnolias grow naturally in soils that are deep and rich in rotted organic matter. Slightly acidic soil is ideal but magnolias will tolerate alkaline soils containing plenty of humus. At planting, dig a hole about 1m wide and add compost or rotted manure to the excavated soil before returning it to the hole.
Water Young magnolias need plenty of water, but once established and deeply rooted (their root system can span four times the overhead canopy!) they’ll tolerate short dry spells. If watering is needed, soak slowly so water sinks deeply into the soil. Do this fortnightly until regular rain returns.
Fertiliser If soil is deep, dark and rich in organic matter, feeding isn’t necessary. However, spraying the leaves of young plants with soluble fertiliser helps them establish. Spray fortnightly from the time flowering ends until autumn and repeat the following year. When the plants are established, use a controlled-release fertiliser for trees and shrubs. Apply immediately after flowering finishes, topped with a compost mulch.
Pruning In general, pruning isn’t necessary, but you can always remove dead or damaged branches and prune out others to encourage a more desirable shape. Prune deciduous magnolias straight after flowering, cutting back to the raised ‘collar’ found at the base of larger branches. Be careful not to cut past this collar, as this will discourage further flowering and growth.