We had a very slow start to summer, but there have finally been some hot days in January. I for one am glad that the forecast of a lot of rain didn’t eventuate, as many of my trees struggle to receive enough light at even the best of times, because of where my collection is located and also because, I confess, I have too many trees. Did I just write that??
I spent a week isolating at home during January, which gave me a chance to get to those neglected trees that are often the last to receive any attention. For me, they are elms, olives and junipers. I often tend to miss out on giving them the attention they deserve because they are generally so forgiving and can be worked on at almost any time of year, whereas other species’ needs are often more pressing. We all (should) know that junipers, in particular, actually need to be our focus at regular intervals throughout the year, as this is more beneficial for maximising growth and the styling potential of these trees.
To tidy up my junipers I don disposable gloves and gently work through the foliage pads of each branch with my fingers, removing brown needles and any white webbing from caterpillars or the like among the foliage. It’s amazing how such pests can hide themselves from the naked eye, only to be revealed when the foliage is examined carefully! Then I trim each branchlet (if required) by cutting behind a section of growth, but ensuring that what remains has actively growing shoots. In my early days of bonsai, we were told to ‘pinch, pinch, pinch’ the growth tips of our junipers. This practice actually leads to a loss of vigour in these species, as the energy for growth is in those very tips. If repeated too energetically, it can lead to the loss of branches and may eventually result in the death of the tree. So don’t do it!
Some of the days (and nights) have been quite windy, so, as always, it’s 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. They can be placed in trays filled with pebbles or sand to maintain humidity around them. Plants such as wisteria, swamp cypress, lilly pilly, melaleucas and banksias should be sitting on pebbles in trays of shallow water as well, as they are very thirsty species.
Watering is generally best done in the morning, as early as possible. The stomata (breathing pores) of the leaves on our trees close up for the remainder of the day if the plant is stressed for moisture at any stage. Use a watering can or hose with a fine rose to avoid disturbing the soil surface. If hot, windy weather is forecast, mist all foliage and the surrounding area of trees with a spray bottle, to create a more humid environment. Immersing pots in water once a week can help keep plants in good condition. Adding a seaweed solution 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 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 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.
There is still time to repot figs and other tropical species, but once the nights start to cool later in the month it will be too late.
Black pine branches which have matured since forming in the spring may be cut back by up to half, to encourage more compact budding. But do not cut back to where there are no needles.
Many trees have two growing periods in a year: spring growth, which gives new leaves and lengthens branches (high nitrogen), and the second spurt, autumn growth, which thickens the trunk and branches (storing carbon). This latter spurt is the most important for bonsai growers, as it assists in giving an aged appearance to our trees. This is why using an organic fertiliser in the final months of summer is important to support this process.
Continue to shape branches throughout late summer, with the exception of any sacrifice branches, which should be left to grow unchecked. Rotate your trees regularly so all sides get an equal amount of light, to promote even growth and prevent die back of weaker branches.
If we do get late summer rain, watch for any 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.