Tree Tips

December 2025

End of Year Holiday and Christmas Pot Luck (and Auction!)

This year we will be getting  together for our Pot Luck Christmas Dinner and Year-End Auction this Thursday, December 2nd. Whether bringing a main course, side dish or family favorite let's all share the spirit of the holidays together. I’m bringing a spicy lima bean casserole - my family favorite. Remember also to bring in bonsai related items: trees, books, tools, pots, etc. as well as your checkbook for the auction and next year's dues. $50 for single, $60 for a family. This auction is 100% to the club and covers the many expenses we incur throughout the year. So, Ho Ho Ho, be as generous as you can. It's always fun and you might score some neat stuff. 

It looks like the early winter will have reasonably mild nights near 40º and days in the lower 60s but watch out for colder weather between now and the end of January. We had some rain in November and I hope we get some more storms this month, like once a week. Check trees for water needs. Some aren’t using much water and others are really thirsty. Move and rotate your trees so those trees needing more water are together. All shade cloth can be put away until spring. Tropicals and sensitive trees are vulnerable to cold snaps and the most likely time is now through the end of January. Bring them into a garage or a sheltered area near heat, or put an incandescent light bulb (if you can find one) near them to give them some warmth at night. 

Wiring & styling—conifers

Winter is a great time to wire and style your conifers. You can clean out the crotch growth in conifers, deciduous and broad leaf evergreens unless you need a new branch to replace a weak older one that won’t back-bud. Also clean out and trim back excessive foliage in the upper part of the tree to allow sun to strengthen lower branches. Start from the top so that you create a pyramid shape where no upper branch is shading the tips of the next lower branch. Hardened older pine needles can be thinned out without harm to the tree. Multiple buds from this summer’s candle pruning should be reduced to two. Remember that you need to stimulate new budding close in to keep the tree healthy, happy and compact. It allows light in and also gives you room to apply wire.  Also remember that June candle cutting is done on more refined trees to increase ramification, not on trees that need basic branch structure. We candle cut when we have set the branches in place and want to ramify from close-in to the trunk.

Wiring & Styling—deciduous trees

Once half your leaves have turned color, strip the remaining leaves off your deciduous trees. We want to work on them as they are going into dormancy, not when they are totally dormant. They tend to bleed when fully dormant.

Broad leaf evergreens like oaks, citrus and olives can have their upper leaves cut in half to allow more sunlight into the interior core of the tree to strengthen those lower branches, thus preventing them from weakening and eventually dying. Weak branches should not be totally stripped of interior foliage so that they can gain strength with the heavier load. We will cut back to this interior area from now until early February to create back budding.

If you cut back when you strip off the leaves, the shoot shouldn’t bleed. If the wound does drip sap excessively you should wait until late winter to cut back when you transplant. Also, spray the bleeding wound with cold water as this sometimes helps stem the flow of sap. The next month will see almost all of the leaves fall from your surrounding landscape trees as well. Get them off your bonsai. You don’t need or want hiding places for over-wintering bugs and slugs. It is always a mess this time of year and I have to clean them up and get the weeds, which never stop, out of my pots.  

Regardless, it's a good time to study the future of your trees and decide which branches to eliminate and which to keep. Leave a little stub when cutting back at this time of year.   

General seasonal upkeep

Rotate your trees! Give all sides access to the sun. The sun is very low on the horizon and will give you one-sided growth if you don’t turn the trees. Watering is important especially for evergreens because the foliage mass acts as an umbrella just like in large trees in nature, and sheds the water out to the drip line. In our case the drip line is outside the perimeter of the pot. So make sure you check your plants water needs regularly. Put a block of wood under one side of your pot to help drain excess water. Alternate the block from side to side every other week.

If you haven’t done it yet, put super phosphate on the soil. But don’t forget that some nitrogen is needed to enable the other components to work. Some fish emulsion or cottonseed meal should be enough. Pay attention to any trees that have young growth pushing or are semi-tropical varieties. Again, the freezing cold weather may cause some damage, so protect them.  

Dormant spray. Start it now. I like to spray the foliage and trunks with Ultra Fine® oil or a fixed copper spray like Microcop® or Bordeaux® dormant spray for peach leaf curl prone plants such as stone fruits and pomegranates, as well as on deciduous trees.  A few years ago, Barrie Coate thought very highly of using the oils as a preventive measure. Be sure to wash off oil after an hour on conifers so they don’t burn. Separately, you can use lime sulfur except on Ume (flowering apricot). I spray three times: at Thanksgiving, New Year and Valentines Day just before bud breaking. (P.S. Lime sulfur will turn your copper wire black but shouldn’t hurt the tree.) Do your spraying now and you won’t have as many problems later.

Preparing for repotting

Mix your soils and clean your pots for transplant season. Gear up for transplant season right after New Years Day. I will be doing a transplant program on the third Thursday of the month, January 15th, our first meeting of the New Year. See if you can get supplies (soil, tools, pots, wire etc.) from Drew Tucker in our club or Jonas DuPuich at Bonsai Tonight, or Peter Tea or online. Or pick some up at the December auction, if they are offered. 🌳