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A Basic Guide To Bonsai Seasons ( Summer ) part 2 of 4

Updated: Jan 7, 2023

We all know we go through 4 different seasons in Bonsai, for most parts of the world anyway. Today we will take a look at the general guidelines for work performed in Summer.


Summer is almost a more exciting season for Bonsai for me because during spring we are letting the tree fluctuate in growth and looking after the health of the tree which is super important, But in summer time we can come back in and style the tree back into shape and even expand on our initial designs with the added new growth if we decided to keep any. Summer is also a time though where we need to be very diligent with our watering and making sure the tree has enough moisture to function properly.

PRUNING : Summer pruning is different compared to our spring pruning as by this point in the growing season we should have given the tree enough time and resources to restore its energy and we are now in an energy positive state. We can now turn our focus on pruning to aesthetic decisions and work some more on our design of the tree. Now there are still a few health maintenance points to keep in mind during the summer period, We want to keep the canopy open and free flowing in terms of air penetration. We also want to keep the canopy open enough to allow light penetration. Also remember that the more foliage that is on the tree during the summer period the quicker it will transpire and drain its water resources in the Bonsai Pot. Now I'm not saying that you should come in and reduce the trees canopy to help reduce the amount of transpiration happening but I'm just pointing out that 2 of the same trees with different amounts of foliage may very well need 2 different amounts of watering.

Summer is our time for Black Pine De-Candling as well. We have separate articles on that so we want go fully in depth but as summer approaches its a good time to re educate yourself on timing and technique because Black Pine De-candling is very timing critical.

In the summer time if a deciduous tree like a maple loses all its leaves or for some reason you do a complete defoliation ( not recommended ) you will need to move that tree into full shade otherwise you will cook the trunk, you will see black spots begin to appear on the trunk and the tree will likely die.

Re-Potting : Repotting in summer is a very dangerous move for most species. The reason for this is due to the heat, the tree is moving water through its trunk and foliage at a rapid rate to keep the tree cool and hydrated. It does this by pulling water up through the root system, If we come in and cut the root system and reduce its ability to move water by 50% or more then the tree will struggle to re hydrate and possibly die. If the tree does survive the process it will be slowed down greatly due to the fact it will need to spend the rest of the growing season trying to re establish a root system, if Re-Potting is done at the right time at the end of winter / early spring the tree will re-establish that root system much quicker and wont have to deal with rapid transpiration. Now there is a slight difference with tropical species such as ficus, a lot of people repot late spring early summer but before temperatures get too out of control. Ficus will re establish a root system quicker when its warmer, but don't allow it too get too hot otherwise the ficus could still suffer. If it gets too hot for a ficus repot in early summer wait till autumn.

WIRING : Wiring during summer is much safer then doing it in the spring period, my suggestion is though if you have very major bends that need to be done then hold off till autumn, But general branch and ramification wiring can be done no issues during the summer period. When we talk about major bends im talking about bends that need Raffia or the use of a jack to get the bend done. The tree will be too stressed in summer for this and the tree wont have entered it stage of vascular growth yet which is where we can get away with larger bending work.

WATERING : Ok summer watering, the most important time of year to get this right! 1 missed day could spell the end for your tree. Now we have always spoke about the fact that there are a lot of different factors that will determine how much you water a tree from weather, soil type, pot size and species type to name a few. But i can tell you 1 thing for sure, you will be watering at least once per day during the summer time. Now me for example i need to water 2 - 3 times a day during our Australian Summer, but i also use in organic material such as Akadama, Pumice and Kiyru. If you work all day and are not home to water i suggest putting up at least 30% shade over your trees or finding a spot during summer that has afternoon shade for your trees during the hottest part of the day. This will allow you to give the trees a very thorough watering before you leave for work and then maybe a watering when you get back home if they require it. If you are gone all day and the trees are out in the sun all day you may have trees that completely dry out by the time you get back home. Misting systems can help slow down transpiration by providing an external source of cool on the Foliage, trunk and pots but don't totally rely on just that alone as mist evaporates very quickly.

If your hose is exposed to the sun all day allow it to run for a minute or so until the water runs completely cold before watering, if you turn your hose straight on and begin watering your trees you might as well be watering them with boiling water. Water sitting inside a black hose in the sun all day gets very very hot and applying that hot water too your root system can be a fatal mistake for your tree so always just remember to allow the hose to run before begining to water.

Try to avoid overhead watering softer leaf trees but trees with a hardier leaf or needle can get some water over the foliage to help cool them down, Softer leaf trees run the risk of burning the leaves if they have water droplets sitting on them. Now I've never personally seen this but it cant hurt to follow. I give most of my conifers a good overhead drenching if we still have a few hours of heat left in the day. Don't soak the foliage if it is close to sundown as that moisture could sit in the tree all night. With my mid day watering i also hose down the benches and surroundings just to cool everything down and create a little extra humidity.

Summer is a great time to have some sort of top dressing on the trees soil as well such as sphagnum moss to help slow down surface evaporation. Keep in mind though if you have a nice layer of green moss on your tree don't water to the moss, water to the tree. Moss will dry out super fast in summer, if you re water the tree every time the moss dries out you'll over water. If you want to get your moss green again during the hot days simply use a spray bottle to mist the moss and put moisture back in it. This is the same though out the year and is good advice for trees with moss on them, dont water because the moss looks dry, only water if the trees soil is dry.

That's it for this weeks article on summer care. i hope you have gained some extra knowledge and i will see you next week for Autumn.

Until Next Time, Enjoy Your Bonsai Journey.

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