Autumn is well and truly on us now, with cooler nights and crisp mornings. 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 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 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 if possible, move your figs to more protected areas under cover, so they are minimally impacted by the cold weather ahead and frosts in particular.
Check species such as figs (particularly ‘Little Ruby’), pyracantha, cotoneaster and olives for scale insects and treat appropriately with pest oil or a systemic insecticide, however, you can scrape them off if you prefer not to use chemicals. The presence of ants can be a good indicator of a scale infestation, as they ‘farm’ the sticky honeydew the scale secretes, and sometimes can even move the scale 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 ‘carcasses’ still remain on the branches and leaves, so will need to be removed later anyway. If your trees are in a sheltered position (like mine are) some insect pests are able to survive over the winter period unhindered, so always remain watchful.
Carefully remove any moss that has grown over the trunks and/ or 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-tended trees. I try to get the weeds out before they go to seed, as growing my own weed seeds only make 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.