Oak Styling and Development

There are many ways that oaks adapt to the landscape but the form most associated with oaks that grow on the rolling hillsides and open areas of the landscape is embodied by rounded foliage silhouettes grounded by a buttressing trunk that splits into several vertical and slanting leaders. These trunks, in turn, meander up and around, casting branches every which way to form sub-crowns in the informal umbrella­like shape. Oaks are usually broader than they are tall and are marked with a fountain­like upward and outward branching theme with the tips drooping slightly at the exterior edges.

Unlike pines which are typically styled with defined branches and pads, oak branching takes off more randomly with riotous. Heavy interior branch movement, eventually reducing down to fine twigs at the edges of the silhouette.

The beautiful movement in a mature tree in the landscape is a result of years and years of multiple shoots extending, competing for sun, crowding out weaker shoots, being damaged in windstorms and by insects, wildlife or pathogens. Some just die out and others fill the void in the canopy vacated by those dead shoots and branches.

All of those shoots start out straight. It is the incremental nature of growth over time that yields the wild curves in trunk and branch. In Bonsai, we try to compress those years of movement by wiring those straight shoots with exaggerated curves. When wiring a bonsai branch, the most important section is the first three to five inches. Growth longer than that can be allowed to grow straight to thicken up the interior curves and help them set faster. Bending creates a succession of arcs from which the next shoots will come. This series of arcs, as opposed to straight lines, creates a more natural feel to the tree.

Bonsai Training

As much as possible, working with new shoots yields the best results. They can be manipulated freely without having to fight an old leggy branch with dead patches and aging, reluctant latent buds. Young shoots and branches devote most of their energy to growth and expansion. Older branches lack the same dynamic energy for growth as they must allocate resources to maintain heartwood, sapwood and dead stretches due to shari and jin.

For an oak, the phyllotaxy, or the arrangement of leaves on a shoot, is five to two. This means that between one leaf and the next one in the same position on the shoot there are five intervening leaves rotating twice around the shoot at about 144° between leaves.

Trivia? Yes. When we bend curves in the oak shoot, we can use this growing feature to add randomness to the branch angles and get that meandering oak characteristic.

After allowing the fall growth to mature and store energy in the vascular system of the tree over winter, the tree can be cut back hard in mid-January on both deciduous and evergreen oaks to the point where new shoots are desired. Sometimes, even on an evergreen that means going back to bare wood, leaving no green growth left on the branch. Scary stuff! But forge on! Remember to seal the large cuts with cut paste. To develop branches from scratch on evergreen oaks, try the following procedure.

Year 1. After the above cut back in January, new shoots pop on native oaks at and just behind the cut appearing in late February-early March as the days lengthen and it begins to warm up. New growth is allowed to harden (they become less succulent, turn darker in color and get stiffer, waxier leaves) usually by mid to late April. (Cork oaks are usually about four to five weeks later). New shoots are wired out four to five inches or so in an inclining slope, bending the shoot mostly up and out and up and out, then a little side to side movement in this same section. The shoot tips should be allowed to grow unrestricted for the remainder of the year but remember to remove the wire when it starts biting in, usually in six to eight weeks.

Year 2. Next January cut-back, leaving three to four inches of the new curved branch area. Repeat last year’s process; cut, harden, wire, remove wire, grow. But this time there may be lots of shoots on the three to four inches. Wire three of the shoots (backside, front side, and top) in the same manner as Year 1.

Year 3. Next January, the three secondary shoots from last year are each cut to two to three inches, wired in April after hardening, then choose six shoots (two on each of the three shoots from last year) to wire. Again, remove the wire after the bends are set and, at this time, cut back each of the six shaped shoots to two to three inches. When new shoots come out and harden, wire two shoots and let the branch set in position yielding 12 tertiary shoots. Remove the wire when the bends are set and leave until next January’s cut-back.

Year 4+. From then on refine the branches by cutting back to two to three leaves in January, and each time there-after, as the shoot elongates and before it hardens, leaving a side shoot and leader. Wiring and big cuts won’t be required other than to occasionally adjust the styling or thin over crowded areas. By now, the branch will be well on the path to having that nice ramified oak appearance with good transitional taper.

Defoliation every year or two, can help reduce leaf size after growth hardens, up to about August 1st. Be cautious thereafter. Only defoliate on healthy trees!!

Occasionally, allow a random interior branch to grow outside the canopy without wiring. When it gets past the established silhouette, strip the leaves up to that silhouette and allow it to then run unobstructed. This sacrifice branch will give better transitional taper for the tree where needed, as well as create mature bark, especially with cork oaks. Young, rampant growth is the key to getting good bark. Eliminate the branch when it has accomplished its job and before it weakens the area around it.

We want those interior branches to remain strong because, no matter what we do, the tree will eventually expand and become leggy. Then we need those branches to cut back to and restart the building process. Who said that Bonsai is not perpetual fun?

Ramification maintenance. When the desired branch shape is achieved, pinch back the extending shoots, as they open, at the edges of the branch silhouette. Allow shoots to fully extend if you need to fill a hole in the branch shape.

Deciduous oaks can be cut back in January and thereafter to two to three leaves in May after hardening and maybe once again if it’s extremely strong. Total defoliation of deciduous oaks late in the year (August forward) is very risky and hard on them, using up a lot of the energy reserves of the tree. They can sometimes shut down and wait until the following year to produce new shoots, or throw out a few shoots while cutting off and killing some branches you need. However, after leaf hardening, early defoliation thru June will reduce leaf size and if paired with cutback can generate new shoots as well. If you can’t defoliate, cutting back and thinning the upper section of each branch crown will allow light below, will save interior leaves from dropping and shoots from weakening. Keeping them super healthy and active is important.

Tree Stage

Bonsai Care and Development

Operations and Purpose

Timing

Trunk Development Primary Branches

Secondary I Tertiary Branches Twigs and Foliage Maintenance

(Revert back to earlier stage when necessary to solve problems)

Whole Tree

  1. Sun I Temp I Wind – adjust growth cycle – damage control
  • Water – maintain proper hydration
  • Soil I Pot- size and composition / volume and shape
  • Transplant interval – speed-up / slow down growth – refresh
  • Fertilizer- growth regulation – amending for health
  • Pest Control – treat and/or get ahead of Insect and fungus

Targeted Operation

  • Cutting Branches or Leaves Pinching- shorten internodes – maintain shape – bifurcate Pruning – determining shape – bifurcate

Thinning – Open cramped areas – save inner branches

Defoliation – reduce leaf size

  • Wiring – Shape Branch / Design

Dec. 21 Winter Solstice

Mar. 21 Vernal Equinox

June 21 Summer Solstice

Sep. 21 Autumnal Equinox

Angle/ Intensity of Sun Temp

Perform Operations at the Appropriate Times in the Plant’s Growth Cycle

Hormones Auxin · Apical Growth

Cytokinin – Lateral Growth

Pinch/ Prune Hint

“rule” of 2 –Leave 2 buds / leaves – a leader and a side shoot

Wiring Hint

Bend in toward main, then bend out toward sun.

This handout was prepared by John Thompson (2019)

jtbonsai@gmail.com

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