by Terry Erasmus July 11, 2016

With the shortest day behind us now I can safely say spring is on its way. This realization brings with it the need for planning for the season which begins to loom before us. This sounds very ominous and I write it so intentionally. Spring would certainly rank on any bonsai artists calendar as the busiest season of the year.

Its not all work though, after the cold and wet winter the warmer days bring with them new life in us and our trees; a sense of new beginnings and perhaps {hopefully} rejuvenated ambition to really get stuck into your collection during the growing period which lies ahead.

Hackberry bonsai trees

Image caption. After having to look at our trees in the nude for the last few months, we have a canopy full of bright green leaves to look forward to in spring.

However make no mistake there is a lot of work around in spring and this work is made that much easier if proper planning is done in time. There is nothing worse than waking one morning to find half your collection requiring immediate repotting as the buds have already begun opening and you have no growing medium prepared!

So please use the following list as a guide to help prepare, but you might find some items irrelevant and there may well also be several missing:

Winter pesticide spray

If you have a collection of bonsai, they will usually be grouped together. This proximity between trees can lead to a buildup of pests and diseases over the course of multiple seasons.

An age old method of addressing this problem is to spray lime sulphur.

What are the benefits?

  1. addresses all pest and disease issues which I am aware of
  2. breaks the cycle of these between growing seasons

Lime sulphur should be applied as a spray (and I mean the tree must be dripping with it!) to all trees, deciduous or evergreen. I spray twice, two weeks apart. It works best on scale insects when they are on the move so try spraying when it's not that cold, and course there should be no rain for about 24hrs after the application.

Mealy bugs on bonsai lime sulphur

Image caption. Mealy bugs are sorted out by a repeated exposure to lime sulphur spray.

A lot of people are scared of using lime sulphur on unglazed pots. True, it does leave white stains on the pots for a few months but failure to get the treatment into the soil may mean you do not kill certain pests or fungus which exist there. I therefore don't cover mine.

You can purchase lime sulphur here, or from your local nursery. Just remember that once opened it rapidly loses efficacy so you should not store it.

DO NOT WAIT TO USE THIS SPRAY AS APPLYING IT TO TENDER SPRING LEAVES WILL KILL THEM.

Repotting

When I think spring I cannot do so without immediately thinking of repotting. Soon after that, I recall plenty of sore muscles, being berated for constantly dirty fingernails or traipsing dirt into the house and always being in a rush.

Why we repot

  • Repotting is something which we are required to do with our bonsai trees, to keep them in a healthy condition.
  • Some growing mediums deteriorate and reduce in size, retarding drainage.
  • Roots also develop and eventually fill the small container again impeding drainage but also limiting water penetration.
  • A build up fertilizer residue also alters the pH and may also contribute to the reduction in water drainage and exchange of oxygen depending on the type being used.

I am actually of the opinion that most people repot too frequently, although the frequency does depend on the species and stage of development. A young tree in development phase may require repotting every 2nd year, but a mature pine may only require repotting every 5 years or even longer.

Trimming roots on bonsai repotting

Image caption. Don't use your best scissors when cutting roots as stones damage the cutting edges.

If you would like to learn more about repotting then why not join me in one of my small group workshops dealing with this all important activity.

Repotting Shopping List

Sufficient Growing medium

Must be fast draining and not too moisture retentive. Go through your tree collection and identify the trees which will need repotting this season and work out roughly how much medium you're going to need. Ordering in bulk will save you money, as opposed to repeatedly ordering small quantities - Click here to purchase growing mediums.

Sickle

Pot bound trees are difficult to get out of the pot and it is best to use a sharp implement such as a sickle to make a narrow gap between root ball and pot and thus be able to lift the tree - Click here to shop for sickles

Root hook

A root hook is useful in loosening old growing medium and combing out the roots in developing trees - Click here to shop for root hooks.

Root hook in bonsai repotting

Image caption. A root hook is useful for raking out the roots of the rootball and for getting rid of old "spent" growing media.

Rake

When a more mature tree requires repotting a root hook is too coarse and a rake is needed to rake out the mass of fine roots - Click here to shop for rakes.

Drainage mesh

If the holes of a bonsai container are not covered with suitable mesh then it will simply wash through. Suitable mesh is a mesh which has an apeture slightly smaller than the graded growing medium you are using. Anything small and fine particles will be caught and prevent proper drainage - Click here to shop for drainage mesh.

Soil scoops

A soil scoop is useful for transferring growing medium from a bucket or other bulk container to the pot without messing - Click here to shop for soil scoops.

Wire

I cannot stress it enough - USE WIRE TO ANCHOR YOUR TREE INTO THE POT. Failure to do so may result in your tree being lifted out the pot by a gust of wind, or at least allowing movement within the pot and thus breaking young, tender roots - Click here to shop for wire.

Brush

A small broom of natural fibre is useful in clean up operations after the repotting work has been completed - Click here to shop for brushes.

The above is not an exhaustive list of tools which are useful when repotting. I would furthermore suggest a pair of scissors which you will dedicate to cutting finer roots only, and then a must have as far as I am concerned is a root cutter.

Containers

The word bonsai includes reference to a container, although interpretation of what constitutes a container has become rather vague and abstract these days. I personally prefer to stick with the classic, fired ceramic container but please feel free to experiment if you like. 

Selection of bonsai tree ceramics

Image caption. It's useful to have a selection of bonsai pots to choose from come repotting season. In this way you can choose the best pot for the tree rather than use the only one you have.

If you're not sure how to select a suitable pot for your tree then please do read the in depth article I have written on the subject here.

Whatever you do decide to use as container; whether it be a ceramic pot or piece of recycled tyre you should keep in mind the following:

  • Bonsai is about the combination of tree and pot, the pot being secondary to the tree and should play a supportive rather than dominant role.
  • A mistake I see all too often amongst beginners is that they put their trees into bonsai pots too early. {Read these articles on field growing}. If field growing is not for you, then "over-pot" your tree at least, to allow it plenty of space in which to develop.

Shohin bonsai in small bonsai pots

Image caption. These shohin are planted in very small pots. This means that come summer time people are going to be watering about 3 times a day. If you cannot maintain such a schedule you will either need to resort to automation; plant them in larger pots or don't keep such small trees :)

  • Planting your tree in too small a pot will mean extra work {watering} in summer. Use a pot of manageable size.
  • Try to have an assortment of containers available to repot your trees into. When you are busy with repotting it is nice to have several pots which you can mix and match with different trees. {Read this previous blog post where I demonstrate what a difference a bunch of pots can make to the same tree}. A pot should enhance the tree, and it's usually very obvious when you find a winning combination. If you can't afford to buy new pots perhaps you can organize a pot swap meet with some bonsai friends.

Shop for unglazed containers here and glazed containers here. If you are looking for something special then consider one of these handmade, old Japanese pots from Tokoname.

Grafting Subjects

Every time I repot my maples I look at how I may improve their nebari. The fact is that when you repot, it is the only time you can perform a root graft safely.

Likewise thread grafting can only be done in very early spring when the sap is rising and buds are only just beginning to show signs of swelling.

Approach grafting bonsai trident maples

Image caption. Trident maples take very well to the approach grafting technique as they heal over so quickly and so readily.

What to prepare

Suitable grafting material

  1. For approach root grafts I generally exclusively use rooted cuttings of the same species which I took in autumn 2 seasons ago. {Read more about taking cuttings here} However you may also use 2 - 3 year old seedlings.
  2. For thread grafting you will need some long whips of the same tree or you can use a donor seedling of a few years of age. However bear in mind that if you use a seedling, the genetic characteristics will be different and so that branch might have a different leaf shape, it might have different autumn colour to the rest of the tree etc.

Cuttings to be used for approach grafting

Image caption. Root cuttings are useful to use as approach graft material in the root zone. However use branches from the same tree for approach grafts in the canopy. 

Tools you're going to need for root grafts

Grafting knife

For root grafting you're going to need a sharp grafting knife to create the groove in which to lay the scion. Grafting knives in general are very useful for cleaning cuts to accelerate healing.

Grafting pins

Grafting pins to secure the scion in place as it must absolutely not move - Click here to shop for grafting pins.

Panel hammer

Panel or other small hammer to hammer in the grafting pins.

Wound sealant

Sealer to ensure that the joint between scion and tree is kept from drying out - Click here to shop for sealants

Healed wound on a chinese maple bonsai tree

Image caption. When a proper sealer is used, wounds close as they should like this one which was a large cut on a Chinese maple.

For thread grafting you'll need

Suitable drill bits

Suitably sized drill bit which will be at least 1 1/2 times larger in diameter than the thickness of the branch you will push through it. A power or hand drill will of course also be needed.

Wound sealant

Sealer ensures the point of contact between branch and trunk is kept moist or fusion will not happen - Click here to shop for sealants

If you'd like to learn how to do approach or thread grafting together with repotting, then please consider joining me at one of my small group workshops dealing with these topics.

Fertilizer

The initial spring push of growth will be supported by fertilizer you gave the tree in autumn. However pushing all those new leaves takes a lot out of the tree and so you need to begin replacing those lost nutrients.

Once again how much fertilizer and when you give it will be determined by the level of development of your trees. A young developing tree can get as much fertilizer as you can afford to give it from the beginning of the season. A mature tree on the other hand needs to be a little deprived, so you might start to give it some light fertilizer a couple weeks into spring and then gradually a little more as the season progresses. 

Everyone has their preference for what fertilizer they use. Generally the consensus is that organic is better than chemical types, not least of all as you cannot do as much damage with organic as you can with chemical fertilizer by dosing incorrectly.  You may prefer to foliar feed than to use solid fertilizers or drenches. It does not really matter how, only that you do fertilize. You cannot work on a weak tree, period!

Bonsaiboost results with olive bonsai trees

Image caption. A sachet of BonsaiBoost pulled away to expose the feeder roots growing up towards the bag to the source of nutrients. I have never witnessed this response to any other fertilizer.

If you want to know what I use exclusively then take a look at BonsaiBoost. If it is good enough for my teacher,  a 3rd generation professional to use on his masterpieces then it is good enough for me. Still not convinced? Read all the reviews below the product then.

That's about it I believe. So in summary make sure you spray all your trees before bud break with lime sulphur. Make sure you have everything ready for repotting and especially enough new growing medium. Lastly purchase or make enough fertilizer for spring to ensure your trees grow healthily so you can work on them later. 





Terry Erasmus
Terry Erasmus

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