What I have learnt trying to grow our native plants.
1. Planting under Gum Trees
To maximize your success establishing new plants to grow under gum trees, plant them as close to the trunk as possible. The reasons you do this are: there are very few tree feeder roots to rob your plant of nutrients and moisture. The second and less obvious is all about increasing the moisture of the soil.
During rain, a lot of water runs down the trunks of the tree and hence toward your newly planted plant.
2. A Great Screening Plant