This summer, we have had quite a lot of rain and cooler days than is normal for this time of the year. We have also had COVID 19 restrictions in place, possibly limiting the movements of many of us during the holiday season. I’m sure this has given most of us more time and motivation (if we needed any) to attend to our trees than in recent years.
The heat has finally arrived, however, in late January as I write this and there’s more of the same ahead, so it’s still important not to let your trees dry out. Some smaller or shallow pots may require watering more than once a day and should be kept in a more sheltered position for protection from drying winds and the hot sun. Pots prone to drying out can be placed on trays with pebbles to maintain humidity around them or stand the pot on something such a clean polystyrene meat/fruit tray for the same effect. Plants such as wisterias, swamp cypress, lilypillies, melaleucas and banksias should also be sitting on pebbles in trays of shallow water, as they are very thirsty species.
Watering is best done in the morning, as early as possible. When watering on hot, windy days mist all foliage and surrounding area of trees to create a humid environment. Immersing pots in water once a week can help keep plants in good condition and prevent the soil drying out and becoming ‘water resistant’. Adding a seaweed solution such a Seasol to the tub when you do so, can give an added boost to stressed trees.
Keep your maples and other deciduous species sheltered from hot, dry winds and preferably under shade, to prevent burning of their leaves. Continue to fertilise all your trees through the latter part of summer, but don’t do it on very hot days, to avoid burning the roots. Any deciduous trees which have been defoliated earlier in the summer should be placed in a shaded area until next month and then only exposed to sun when the temperatures are not too high. The new set of leaves will be smaller due to defoliation and colour better in autumn because they will have a higher concentration of sugars.
By now, you should have defoliated any figs in your collection and have a good flush of new and smaller leaves. There is still time to repot figs if you haven’t yet got to them but once the nights start to cool later in the month it will be too late. I usually work my way through my figs from Christmas through January, defoliating every one in my collection and repotting at the same time, if they need it. To defoliate correctly, just cut through the stem of each leaf to remove it. This prevents the loss of too much sap from the tree. The stems left behind then drop off within few days.
If we get more rain and the resulting high humidity, watch for any powdery mildew appearing on crape myrtles and oaks and treat appropriately. Eco fungicide, for example, is quite effective and safe but needs to be re applied every 7-10 days.
Many species of trees have two growth patterns in a year; spring growth which gives new leaves and lengthens branches and autumn growth which thickens the trunk. This latter spurt is the most important for bonsai growers, as it improves the appearance of age in our trees. This is why using an organic fertiliser in the final month of summer and early autumn is important.
Continue to shape branches throughout late summer, with the exception of any sacrifice branches, which should be left to grow unchecked. Rotate your trees so all sides get an equal amount of light, for even growth distribution.