What to do this month

Updated 2022/05/03

What to do in May

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Autumn and the days are cooling down with occasional rain.  But beware of warm days.  Little bits of rain are often not enough to thoroughly water your trees.  Often trees with a lot of foliage will prevent the water from reaching the soil.  Trees standing in protected areas (like close to a wall, etc.) can also not receive any rain.  Keep track of the moisture in your trees’ soil and water accordingly.

Growth on deciduous trees has stopped and several already lost their leaves.  Trees like maples show beautiful autumn colors.  Some White stinkwoods will already be without foliage.  Deciduous trees that have been defoliated during summer will lose their leaves later.

Several olives are showing new growth.

Don’t feed deciduous trees but evergreens showing growth can be fed.

Do not prune any of the deciduous trees.  Pruning deciduous trees now will cause the trees to start pushing new buds.  These new soft buds will only weaken the tree before they will stop developing or even die off during the winter.  The tree will also not get enough rest and this can cause smaller branches to die back.

Do not pot any trees at this stage.

Remove moss from trees with soft bark, like cork bark elms, acacia etc.  Leaving the moss on the trunks will cause the bark to rot.  Also remove moss from the soil.  Moss retains a lot of moisture in the soil which can cause root rot on trees like olives.  Moss can be killed by spraying it with vinegar and then carefully removing it with tweezers.  Carefully remove your moss and place it in single layers in a shallow seed tray and keep it wet until spring.  Then you can place it back on the soil again.  You can also spray the moss with vinegar (undiluted grape vinegar).  The vinegar will kill the moss and it can then be carefully removed with tweezers from trees with soft bark.  Do not spray the leaves with the vinegar.

 Check wire on your trees.  Trees are putting down a lot of wood on their trunks and branches and can cause wire bite.  If wired branches haven’t set yet and tend to move back to the original position, wire the branch again but in the opposite direction.   Be careful when you wire trees this time of the year.  Branches are very brittle and can break easily.  So be careful when bending branches.

This is an important time in keeping track of the development of your junipers (apex growth) as well as the pruning and development of your pines. 

If the new growth on your pines have hardened off you can start feeding them.  Feed young pines that are in the development stage every four weeks and older pines in their refinement stage every six weeks until end of winter.  This will help the pine to build up strength for spring pruning.

You can clean up both black as well as white pines now by removing old needles.

Keep weeds under control. 

Remove dead leaves from the pots and shelves.  Dead leaves only supply hiding places for pests. 

You can start cleaning and sterilizing your shelves with a strong mixture of Jeyes fluid end of May.  Remove the bonsai from the shelves.  Do any necessary repairs and remove all old soil and leaves from the shelves.  Then spray the shelves with a strong mixture of Jeyes fluid.  Wait till the smell is gone before replacing your bonsai.

Pest control

Deciduous trees that already lost their leaves can be sprayed with diluted lime sulfur.  This can be done towards the end of May.  Spray again 10 days later to kill pests that survived the first spray.  Mix the lime sulfur with water in a ratio of 1 part lime sulfur to 30 parts water.   Spraying deciduous trees with lime sulfur while they are dormant will kill off unwanted pests and their eggs as well as other diseases.  Cover unglazed pots when you spray the trees with something like glad wrap to prevent the lime sulfur from staining these pots.

You can also disinfect old pots and training containers with Jeyes fluid before reusing them.   

Thrips  – Also look out for signs of Thrip and wooly aphid on your Wild Olives.  On the first sign of marks on the Olive leafs spray your trees.  Look for white fly on the underside of the leaves of Olives.  Spray with Rosecare or Plantcare or apply Koinor as a soil drench to control Thrip.

Alliette  –  Spray your olives with a preventative spray for root rot.

Start shopping around for new potential bonsai stock.   Most of the trees in nurseries already stopped developing and are only putting down hard wood, increasing their trunks.  Shop around to be first to find the best stock. 

Also start looking around for good compost and other ingredients for your soil mixtures so that in winter you know where to find the best soil for your trees.

Winter pruning is around the corner.  Make sure your pruning tools are sharp, oiled and sterilized.

Sharpening tools

Make use of a good quality sharpening tool to sharpen your tools.  Tools are expensive and using the wrong sharpening tools can damage the tool beyond repair, causing damage to your bonsai.

Sterilize tools

With all the new diseases around now is a good time to learn to regularly clean and sterilize your tools.  A good method is to lace your tools in an alcohol like mentholated spirits.   Don’t use heat like open flames to sterilize your tools.  Excessive heat can affect the hardness qualities of your tools, affective losing their sharp cutting edge, etc.

Regular sterilization help prevent the spreading on diseases between trees.  Since we prune our trees we cause open wounds that’s the ideal entry point for diseases to enter.


Collecting trees 

You can start collecting Wild Olives in May.  Olives can also be potted from middle to end of May till August.

Make sure your tools for collecting trees from the field is also ready, sharp and in a good condition.

You will need a strong spade, saw, pruner and good set of gloves to protect your hands.

If you are not experienced in collecting trees then ask one of the experienced members to give you some advice on what you will need and what you need to do.  It’s a terrible waist to collect a tree from the wild and then to kill it because you don’t have the necessary knowledge on collecting trees.

Also remember to first find the bonsai in the tree that you are about to collect before digging it out.  I’ve seen many trees been collected at club digs by over eager members who then afterwards have no idea of what to do with the tree.  Ask an experienced member to assist you in your choice.  If you can’t see the bonsai in the tree then rather move on.  Look for another tree.  Don’t remove a tree from the field if you’ve got no use for it.


Also visit our face book page at ‘Stone lantern bonsai nursery’ for more articles, photos and events.  Please feel free to make suggestions on how to improve the page and what you would to know more about.


Also visit our face book page at ‘Stone lantern bonsai nursery’ for more articles, photos and events.  Please feel free to make suggestions on how to improve the page and what you would to know more about.


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