Autumn has finally arrived with cooler nights and crisp mornings. It’s a good time to take a breath for now and take stock of how the trees in your collection have improved during the last year.

We’ve had a lot of showery weather of late, so watering thirsty trees has probably not been a priority like it is in summer. Keep your deciduous bonsai in full sun if possible at this time, as this, combined with cooler nights, should improve the colour intensity of autumn foliage. If you are in the market to purchase more deciduous species, this 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.

Make sure to regularly clean up any fallen leaves on the benches or soil surfaces, as these can harbour fungal disease and insect pests, which may have a negative impact on your trees in the future. I usually have a lot of trouble with powdery mildew on my crepe myrtles during summer and early autumn, so those leaves in particular need to be cleaned up and thrown away. 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. The presence of ants can be a good indicator of a scale infestation, as they ‘farm’ the sticky honeydew secreted by the insects and can even sometimes move the scales from one plant to another! Very annoying if your trees are kept close together like mine are. Remove as many of the insects as you can manually before you spray, as even once they are dead, the dried out ‘carcases’ remain on the branches and leaves, so will need to be removed later anyway. If your trees are in a sheltered position (like many of mine are) some pests are able to survive over the winter period unhindered, so always remain watchful.

Carefully remove any moss that has grown over the roots or up the trunks of your trees, trying not to damage the bark underneath. I use a soft toothbrush on some of my trees with smooth bark to solve this problem, but you have to be a lot more careful with species with rough or corky bark, so as not to do any damage to the beautiful bark which adds to the aged appearance of the tree. Persevere with the removal of weeds, as they seem to magically appear as soon as we get any rain. 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-tended trees. I try to get the weeds out before they go to seed, as growing my own weed seeds only makes the problem worse!

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.