Almanac

Our bonsai are dormant, or nearly so, in January. But this should not be an idle time for the bonsai artist.

This is the season to do clean up chores. Remove dead leaves from pots and benches which may harbor insects and fungus. Wash empty pots with a dilute mixture of soap and bleach. Scrub lime deposits with Sandflex or other coarse textured sponge. Rinse and dry in the sun.

This is the best season to study the design of each bonsai by carefully reviewing the branch structure, trunk line, and pot placement. Make a list of the trees which require repotting in a few weeks. Take a few photos to get a more objective view of the tree. It is too early to fertilize (except lightly for some conifers) but the right time to add trace elements. January is the time to apply Dormant Spray and insecticide to kill mites and insect eggs.

Take this time to remove some (but not all) old needles and to reduce shoots to improve balance and interior light to black pine bonsai. A few alternating old needles should be left on the branches in the horizontal position to offer a chance at interior budding. This is also the ideal time to evaluate your needs for bonsai soil components. Obtain those components and to begin sifting and mixing bonsai soil based upon your repotting plans. Most bonsai texts suggest not to repot in January, but our climate zone will permit repotting of some species (pines and junipers) by late January in temperate years. Deciduous species should be kept in shady and cooler areas to avoid early budding during unexpected warm periods. If a deciduous tree does sprout early, however, it should be moved into the sun, because new growth that develops in shade tends to be weak and leggy.

We are starting the repotting season in our climate zone. The more question is always “why” rather than “when” to repot. Repotting, like any bonsai technique, should be performed with a purpose, rather than by some arbitrary schedule. Deciduous trees should be repotted first and conifers later, although junipers may be repotted now as well. The ideal time to repot maples, in particular, is when the buds become red and begin to swell. The tree has the maximum stored energy just before bud burst. Too early is better than too late.

Once trees are repotted, be careful to protect them from a sudden hard freeze. Trident maples will tolerate very aggressive root pruning. Do NOT bare root conifers; old garden soil should gradually be removed over 2-3 repottings from conifers.

After repotting, trees should be left out in the sun (contrary to old advice) as heat from the sun will stimulate root growth. All species which are subject to mites or scale insects should be sprayed with dormant spray during this cool weather. This includes elms, and Shimpaku and Prostrata junipers primarily. If a deciduous bonsai, in shade, begins to bud, it should be placed out in direct sun. If left in shade, it will produce weaker, larger leaves.

It is too early to fertilize, but iron, and other soil additives may be added.

Fruit bearing species may be pruned after blossoms have dropped. Cuttings for propagation may be started in late February and grafting on deciduous species should start this month. This is the final month to graft pines and other conifers.

Watering remains dependent upon rainfall and temperatures and must be individualized. Care should be taken to assess wired branches over the next few weeks, because a warm spell may suddenly push bud growth and branch growth causing wire cuts 

March brings us to the end of the primary repotting season. Generally, pines, junipers and other conifers are repotted during this month, as many of the deciduous trees have already begun to leaf out.

As the weather warms, trees which are subject to infestations should be sprayed with dormant spray in order to kill eggs which may have wintered in the crevices of bark and roots. Elms should be sprayed for scale insects and scale junipers need a spring bath to ward off spider mites in particular.

As temperatures and breezes are unpredictable, trees should be checked for moisture daily and water as needed.

Deciduous species that are starting to leaf out should be moved into the bright sun, if they were shaded during the winter, in order to prevent weak leaf development.

Spring moss may interfere with water and should be removed if so. 

Conifers, which have not been transplanted within the last month, may now be fertilized. Trace elements, like iron supplements can be given in dilute solutions.

Deciduous trees which have not yet leafed out may be thread grafted now.  

All healthy bonsai should have new growth and should be out in the sun with air circulation.

It is wise to rotate bonsai 180 degrees monthly, so the foliage gets equal sun exposure throughout the year. Warm and breezy days will require more careful watering. Watering will remain challenging as foliage development (transpiration), wind, temperature and rain will lead to varying water needs.

At the same time, that fresh spring foliage is more delicate and subject to sun and wind damage. Try to keep Black pines a bit on the dry side, as this will keep the new needles shorter and strong. Long shoots on deciduous trees should be allowed to harden off before they are cut back to two or three buds. While cutting or pruning must wait for foliage to harden off, now is the season to pinch back leaf shoots on maples to reduce internodes.

Pines and conifers may still be transplanted in early April. Remember to preserve some mycorrhiza from the old soil and add it to the new soil mix, particularly for Black pines. April (or late March in our zone) is the first month to fertilize conifers and broad leaf evergreens. Maples and other deciduous species should not be fertilized until May (to reduce internode length.) The key point is to establish a schedule to fertilize at regular intervals depending upon the stage of each tree’s development. Use a slow release organic fertilizer. It is preferable to use frequent feedings with light applications (less than manufacturer’s recommended dose) and utilize relatively low nitrogen, and higher phosphate and potassium. Do not feed newly transplanted trees for at least 4-6 weeks after repotting. 

This is also the month to begin spraying with Neem oil for aphids, scale and spider mites. Again, establishing a regular schedule to spray conifers for mites every 2-4 weeks (in the cool early morning hours) of summer will protect scale juniper species from spider mites.

Most importantly, enjoy the beauty of your bonsai in Spring! 

The summer sun is coming soon to remind us that we live in a bone-dry Mediterranean climate.

Remember to rotate your bonsai 180 degrees every month. More importantly, watch species with delicate thin leaves very carefully, like Japanese maple, Hornbeams and Ume. On hot days move them out of the direct light to filtered sun or shade. During summer, those species should always be kept in full or partial shade.

Watering must be more consistent to keep the soil moist as the Spring breezes and warm days will dry out bonsai much faster.

New shoots on deciduous trees may be cut back to 2 or 3 leaves, if hardened off, in order to maintain shape. The one proviso regarding “hardening off” may be very vigorous species like Trident maples and hornbeams.

Juniper shoots may be cut back now for pad development. They can be cut back but only to two buds on each shoot, rather than simply “hedge pruned”. Removing all the Spring buds will severely weaken the tree and retard growth.

Young black pines black pines may be decandled at the very end of May or early June. Be aware that if decandling occurs early, the second growth candles will have more growing time and will be longer next spring.

Check on wires from last fall. Remove them if they are cutting into the rapidly growing branches of deciduous species. Smaller branches in vigorous species like maples will add girth in Spring very fast and the thin bark will cut easily.

Pomegranate, cotoneaster, olive and pyracantha may still be transplanted.

Most species are growing rapidly and may be fertilized on a regular schedule. Consider organic fertilizers every 4 to 6 weeks depending on whether your bonsai is in development versus refinement.

Spider mites will be attacking juniper foliage very soon. Consider Neem oil spray in the cool mornings every 2-4 weeks. If you have evidence of active mite infestation scale juniper species, like Shimpaku, spray thoroughly with Neem oil in the cool morning hours, then rinse off the trees after 2-3 hours. Repeat in two weeks to cover the life cycle of the eggs. This will work for elm scale as well. 

By now all healthy bonsai should be leafed out and new growth hardened off.

We are entering the hot season. Remember to rotate your bonsai in relationship to the sun so that growth is balanced throughout the summer. We will get little rain.

John Naka recommended soaking the foliage, soil, ground, and even overheadshade to increase the local humidity. If the soil is draining well, you cannot “overwater”.

June is the correct month to partially defoliate. The purpose of defoliation is to reduce leaf size, slow growth (to reduce internode length on new shoots), and allows light into interior branches. Defoliation makes wiring easier. 

Defoliating does NOT produce back budding. Some species, such as hornbeams, Japanese maples, and beeches do not tolerate defoliation well.

Cutting or pruning can be done now, both to maintain shape and encourage backbudding in some species. Making large cuts or chops is not advisable now as we are entering the most stressful time of year with our intense summer heat. This is a problematic time to wire new growth if the foliage is soft and green. Wire cuts are a great risk in fast growing, thin-barked species like maples. Some species, such as Trident maples may still be thread grafted this time of year if the green shoots are partially defoliated for use as the graft.

Rapid growing species should be fertilized now.

Stop fertilizing Black Pines (multiflush pines) now. Insecticide spraying should begin now to prevent scale and spider mite damage. Scale (like Elm Scale) can be removed by hand. 

Some experts advise spray should be continued every 2 weeks during the cool morning hours, throughout the summer.

Ryan Neil advises rotating three different chemical insecticides to prevent development of resistance in Spider mites.

It's not uncommon for July temperatures to reach well beyond triple digits. When this happens, You and your bonsai must switch into "survival mode."

Each tree must be well watered at least twice a day. Keep a close eye on your plants. They may require even more water.

Morning sun is generally good for bonsai, but afternoon can be murder on them. Consider placing your trees under shade cloth or beneath a larger tree for protection from the blistering direct valley sun.

The August heat is just as bad as July.

Some species, such as Japanese Maples, may experience leaf burn if exposed to radiant heat from being situated too close to a stucco or masonry wall. If this happens, and it can happen quickly, move the plant to another shaded area.

Many bonsai growers invest in drip irrigation systems to take care of their watering needs. Even if you decide to do this, you must check on you trees every single day. Drip systems are notorious for breaking and clogging. Timers can be finicky too.

Remember, it the valley heat, it only takes a day or two to kill your plants. Make sure to check on them every single day. 

As temperatures slowly return to normal, plants will return to their normal growth activity. Once this is evident (you will start to see new growth), attention should be focused on fertilization to supply the plant with the substances it needs to develop, consolidate new growth, reconstitute exhausted reserves and strengthen itself to best cope with the winter season.

October can bring wide swings in temperature in the Central Valley. Sudden hot breezy days may desiccate young leaves that will not hardened off until later. Watering requires careful attention as weather shifts may call for more or none.

As the Autumn Equinox will leave many trees in the shade and these must be shifted to sunnier spots until dormancy. Watch the shade pat-terns in your yard carefully.

Nitrogen fertilizer should be stopped and 0-10-10 is advised (to discourage sudden green shoots during warm spells.) John Naka advised applying only one half the recommended dose and only to bonsai still growing.

Moss should be removed from surfaces, particularly on roots and trunks. Fine moss may be dried and kept cool or grown on boards or in cans in shady areas. It can be reapplied in early Spring.

Watch wired branches closely for cuts and girdling damage. Tight wire will quickly become imbedding during the Spring growth spurt. 

Remove brown leaves and dried fruit from deciduous trees.

Long shoots on young bonsai should not be cut back hard but only trimmed back slightly, and only after it has hardened off.

Transplanting may be done in cooler weather, but only from one pot to another and not if root pruning is required. 

As Fall approaches, our trees are engaged on two projects: accumulating carbohydrate fuel to help them resist winter stress and building vascular structure in preparation for the Spring growth spurt. Pruning, wiring and defoliating them while foliage is green will impair that process. When more than half the leaves have turned brown, the tree may be defoliated. 

November can be tricky in our Central Valley environment. Cold windy days may dry out soil but there is much less evaporization as the leaves disappear from deciduous species. Unexpected warm days may confuse budding and deciduous trees should be shifted briefly to shady areas. Trees may require watering due to wind losses. Water less but do not allow any species to dry out completely. Feel the soil, don’t just look at it.

Remove dead leaves, fruits and seed pods. 

Remove moss from potted trees. Clean benches. Apply a final winter dose of insecticide or dormant spray.

Remove two year old pine needles, burned or distorted pine needles.

Balancing of black pine may be done by needle pulling from vigorous bonsai. Be certain you understand this strategy before applying it. 

Fertilizing with phosphate and potassium in half strength may be continued through November with conifers, but fertilization should be stopped for deciduous species. This is an ideal time for pruning and wiring junipers. Transplanting is not advisable until Spring, under most circumstances.

This is the season to study forest plantings in particular as the trunk and branch structure is much easier to see when not obscured by foliage.

And this is the season to start evaluating your needs for the coming repotting season...soil components, supplies, or new pots. Most importantly, spend time studying your bonsai and enjoying them. 

Officially, December 21st is the beginning of winter. But here in the central valley, it is not that clearly defined. Fortunately, we can work on almost all bonsai species this time of year, because our mild winters allow us to ignore issues of winter hardiness.

Our deciduous bonsai have almost shed their leaves. The rule of thumb is that once half the leaves on a tree have turned, you may strip the branches clean (assuming you don’t want to enjoy the fall colors.) The advantage of this is that you can keep the dead leaves off your soil and benches, thus reducing the opportunities for insects. Removing all the leaves also provides a chance to study the trees structure carefully and to make decisions about pruning and wiring.

Watering may only be required one or two times per week.

Fertilizing of deciduous trees should stop in November. Cool temperatures shut off microbial activity to break down organics anyway.

Leaves and detritus should be scraped from the soil now. Scrape down a half inch into the soil. Discard this soil if it is broken down and replace it with fresh. Consider whether the deeper soil is broken down. Has it lost its percolation when watering? Has the trees growth slowed too much or are the roots pushing it out of the pot? Should you mark this tree for repotting in the Spring?

Multi-flush pines ( i.e. Japanese Black Pines) have now harden off their new needles. If the tree is strong, shoots may be pruned and old needles pulled to balance growth and develop ramification. This involves complex decision beyond this simple guide. This work can be carried out anytime between December and February and applies primarily to trees in the refinement stages of development.

Although pines continue to grow slowly, winter fertilizing with organics may be ineffective due to loss of soil microbe activity.

Grafting of pines can be done in December through February.

Junipers and other conifers may be pruned and wired in December.

Trees that have undergone heavy pruning and large bends should be allowed to recover before spring repotting. Consider your priorities and plans for these trees.

Dormant spray should be applied now.

Winter is the season to contemplate. Study your trees. Make decisions about design, potting angles, or pot style: a need for repotting? Begin accumulating soil components, sifting, and mixing.

Do you need a new pot? Silly question. You always need a new pot.