Autumn is well and truly on us now, with cooler nights and crisp mornings. We’ve also had a break from all that summer rain, so hopefully your deciduous bonsai will be starting to show some autumn colour. Keep the trees in full sun if possible at this time, as this, combined with cooler nights, should improve the colour intensity. If you are in the market to purchase more deciduous species, autumn is a good time to look around, as you can see what autumn display any new trees are likely to give you each year. Trees are usually pretty consistent from year to year, either turning red, orange or golden before losing their leaves. One of my favourites at the moment is the beautiful, buttery yellow of my ginkgo trees.
Make sure to regularly clean up any fallen leaves on the ground or soil surfaces, as these can harbour fungal disease and insect pests, which may have a negative impact on your trees in the future. Remove old flowers and berries from trees, and move your figs to more protected areas, if possible under cover, so they are minimally impacted by the cold weather ahead, frosts in particular.
Check species, such as figs (particularly ‘Little Ruby’) and olives, for scale insects and treat appropriately with pest oil or a systemic insecticide if you have them. The presence of ants can be a good indicator of a scale infestation as they ‘farm’ the insects, collecting the sticky honeydew the scale secrete and sometimes even moving the scales from one plant to another! Very annoying if your trees are kept close together like mine are. Remove as many of the scales as you can manually before you spray, as even once they are dead, the dried out ‘carcases’ still remain in the branches and leaves, so will need to be removed later anyway. I have a constant battle with black scale attack on the olives in my collection and the marks they leave behind on the leaves mean that my trees are never worth showing.
Gently remove any moss that has grown over the roots of your trees, trying not to damage the bark underneath, and persevere with the removal of weeds. Weeds are a constant problem for me, as my collection is close to an untended block of land next door, with weed seeds very happy to migrate to the soil of my well-watered trees.
Tree growth will generally be slowing down, so reduce the use of fertilisers or use a weaker solution. Seasol can be beneficial year round as a tonic, especially after repotting or when trees are stressed in any other way. Trees like natives will continue to grow in the cooler months while the deciduous species are dormant. As the season progresses, all your trees will benefit from as much exposure to sunlight as possible.