It’s been a wet and cool summer so far. For me this has meant that it’s been quite pleasant to spend time outdoors working on my trees. Sadly though, it’s also meant that I have plenty of weeds to attend to if I can’t find something better to do!
Some days (and nights) have been quite windy though, so it’s still important to keep a close eye on things and not to let your trees dry out. Showers during one day or overnight may not mean you don’t still need to water the next day. 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 sun. Pots prone to drying out can be placed on trays with pebbles filled with water to maintain humidity around them, or stand the pot in something such as a clean polystyrene meat/fruit tray for the same effect. Plants such as wisteria, 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 as 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 have been placed in a shaded area until next month, and then only exposed to sun when the temperature is not too high. The new set of leaves will be smaller 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 fig collection from Christmas through January, defoliating each one 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. Don’t remove the leaves on any weak or thin branches in order to improve their vigour. You should also pinch out the growing tip of each branch, unless you want to allow it to elongate further.
Black pine branches which have matured since forming in the spring may be cut back by half to encourage more compact budding. Do not cut back where there are no needles.
If we get more rain, and the resulting high humidity, watch for powdery mildew appearing on crepe myrtles or oaks, and treat appropriately. Eco fungicide, for example, is quite effective and safe, but needs to be re applied every 7-10 days or after rain.
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 months 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.