Katsura bonsai – tips on starting and caring for a Cercidiphyllum caramel tree bonsai

Autumn foliage on a katsura cercidiphyllum bonsai

Cercidiphyllum, commonly called katsura, can be grown into bonsai that are particularly appealing in fall.

Katsura bonsai facts

Difficulty – difficult
Start from – older tree, katsura seedling or katsura cutting
Season of interest – fall color & fragrance

Cercidiphyllum katsura – not to be confused with the more common katsura maple – is rather difficult to train into a bonsai. However, its peachy-apricot fall colors combined with the delicious caramel fragrance make it a worthwhile endeavor!

How to grow a bonsai from Katsuratree

What to start a katsura bonsai from

There are three ways to grow Cercidiphyllum bonsai:

  • from an old tree or stump
  • from cuttings (either stem or basal cuttings)
  • from seedlings

Growing from a stump or larger tree

Seedlings may seem like a natural place to start, but the best practice to create a katsura bonsai is to start from a older tree or stump.

  • This is because seedlings, trimmed as bonsai, would take decades to grow noteworthy trunks.
  • Much more interesting is to find existing, larger trunks that may have twisted and suffered in the past.
  • When possible, try to work with several specimens at the same time. Your experience will increase two- or three-fold for basically the same effort!

In nurseries, twisted or wounded specimens deemed too ugly to sell make perfect bonsai candidates. Usually they’re already at least three or four years old.

If you plan on starting from an old tree, jump directly to this section of the page:

Growing from cuttings

Start with basal cuttings for a higher chance of success.

  • Select the stems or branches well, since they will form the structure of the bonsai you’re preparing.
  • Once the rooting has started, leave the cutting undisturbed for an entire year. Katsura cuttings don’t root as well or as prolifically as other species of trees. They’re more fragile at the start.
  • Here’s how to prepare cuttings from a katsura tree (basal and stem).

Growing from seedlings

Sowing from seed takes an extra year or two compared to cuttings. However, it’s a great solution that gives you more leeway in shaping your katsura bonsai. You can wire and tweak branches into shape.

  • A nice way is to force the sapling into the desired shape.
  • Remember you can use tricks to trigger sideways growth like slanting the pot, etc.

Seed and cutting bonsai – growing in the ground is a must

For both seedlings and cuttings, a key step to understand is that large trunks can only be reached with katsura planted in the ground.

Growth in the trunk of a tree is directly related to the volume of leaves and roots above and below ground. Large volumes require a thick layer (or growth ring) with lots of sap-channeling veins, whereas a few sparse leaves will only require growth as thick as a sheet of paper.

  • So to thicken a bonsai trunk, growth must be allowed to flourish at some point.
  • The art of bonsai isn’t so much “growing” a bonsai as it is “halting the growth” of the tree at a desired point in time.
  • This delicate balance is what makes bonsai seem like timeless pieces that never age.

Alternate growth in soil and structural work on the bench

Consequently, the best practice to form and shape a Cercidiphyllum bonsai from small seedlings or saplings is to alternate two different periods.

  • On one hand, growing in the soil is essential to build the plant up.
  • On the other, forming the tree on a workbench must happen for the tree to take on the desired shape.

The time slot available for forming branches is only a couple weeks to a month every year, especially for katsura:

  • For katsura, older wood is brittle and breaks easily.
  • It’s very difficult to “bend” wood that is more than a year old.
  • Any shaping, bending, and twisting of branches must be performed on softwood – wood that has grown in the recent weeks and is still flexible.

Working on a seed-or-cutting katsura bonsai will require alternating between the soil and the work bench for two to five years.

From soil to work bench and back

At the end of spring, the main growth spurt has ended but wood is still tender.

  • Pull the plant out with a clump of soil 12 to 18 inches (15 to 20 cm) across and 8 inches (20 cm) deep.
  • Prune longer roots off cleanly.
  • Place in a basin on a bed of clay pebbles or gravel constantly kept moist. Water and mist the plant daily.
  • Give yourself at most a week or two to work on the branches. Use this time to shape and bend them.
  • When finished, return the plant to its growing hole in the ground and water abundantly.

With Cercidiphyllum, there’s a very high chance that this short 1 to 2 week-period will result in leaf drop. This is because the plant is very vulnerable to drought. Its first coping mechanism is “leaf abcission” (leaf drop).

  • This is nothing to be afraid of. After watering, the tree will put out a new set of leaves that will last till fall.

The pot-in-pot technique, a gamechanger for the katsura bonsai

Work will be made very easy if you follow the pot-in-pot technique for planting your future bonsai.

With this method, two growing pots are used that are only one size apart.

  • The inner pot will contain the plant.
  • The outer pot is buried in the ground, up to the collar.
  • The space between both pots is either left empty or also filled with clay pebbles.
  • For katsura, which has side-shooting roots, it’s best to carve matching openings along the side walls of both pots for roots to shoot out from.

The outer pot is left in the soil at all times. The inner pot can be pulled out rather easily when needed.

  • Of course, before pulling the pot out, roots bridging from inside to out must be cut away.
  • Only a year’s worth of root will be sacrificed every time. The katsura will maximize what space it has better and better.
  • You can use a long knife or blade to this, or a narrow spade with a sharpened edge. Wedge it between the pots and circle around.

It helps to condemn or block the bottom holes of both pots to ensure that roots only sprout out sideways and not down. This makes cutting roots off easier. However, make sure a few of the openings you care are level with the bottom, so that excess rain can drain out.

An added, crucial advantage of this technique is not to be overlooked. You can use the rim of the inner pot to attach and tether wire, slabs of wood, and other things. The structure used to shape the tree will stay with the tree until the next season.

After around five years of this treatment, the trunk will have thickened to a size large enough to be transferred to permanent bonsai pot.

Transplanting the bonsai to the pot

Katsura has a wide and shallow root network. This usually translates in difficulties when transplanting. It’s difficult to not kill an uprooted katsura.

  • Unlike barberry bonsai, ficus ginseng, or Dracaena massangeana bonsai, Cercidiphyllum has more trouble recovering.
  • For those tolerant plants, simply chopping up a larger tree can be enough to start a bonsai, since they readily recover.
  • For Katsura, you’ll have to make sure soil is constantly moist.
  • Hang a shade veil above the bonsai to protect it from harsh sun.

Every time the soil dries up, leaves fall and energy is expended to make new ones. If this happens too often, the tree will drain its reserves and die.

Transplanting to the final pot requires a few steps: culling the roots, cutting back unwanted main branches, and carefully preparing the pot.

Cull the roots

Katsura tends to grow surface roots. Try to maintain this feature when preparing your bonsai.

  • Brush off extra soil to reveal the first top roots.

Attach the root ball firmly to the pot.

  • For example, use a wire that hoops around the root and exits through one of the water-drainage holes.
  • Tie the wire ends around a stick or nail.
  • Tying the root down will make sure the tree doesn’t fall over out of the pot when more leaves and branches grow.

Shape and cut the main branches

On an old, thick Cercidiphyllum shrub, you can cut back branches.

  • Select your candidates based on the shape of the trunk.
  • Aim for curvy, tapered trunks or trunks that sport an impressive wound or defect.
  • Old broken branch stumps also can be maximized.
  • With larger shrubs, you’ll have to transform some of the branches into deadwood to structure your bonsai.

Use various tools such as chisels, metal brushes, and small drills to work off portions of wood and shape the ends of branches.

On a seedling, start wiring the trunk in a harmonious manner.

  • Slant or curve it as you wish the tree to appear.

Shaping smaller branches every year

Smaller branches are shaped in early or mid-summer, on softwood. After that, they tend to become brittle.

  • Note, however, that the bark easily marks.
  • You’ll have to take precautions when wiring these young branches.

Plant in a pot with high drainage

Make sure the pot has excellent drainage.

  • Because roots are often trimmed, wounds might develop root rot if left to wallow in water.
  • Having too much water would spur growth that would grow unbalanced. Long twigs would grow out instead of branching or growing tightly-packed leaves.

Caring for a Cercidiphyllum Katsura bonsai

This bonsai is more difficult to care for than other bonsai.

Watering and exposure

It’s important to not let a katsura bonsai dry out.

  • Check on it daily in case of warm weather.
  • In winter, a weekly verification is enough.

Fertilizer

Bonsai have a tiny amount of soil to draw nutrients from. It’s important to compensate spent nutrients regularly.

  • If you’ve purchased commercial fertilizer, follow what the label recommends.
  • You can also prepare your own fertilizer from weeds. Fermented weed tea is ideal, but any nutrient-rich tea will do.
  • Fertilize monthly during the growing period.

Blooming and fruit bearing

Because the bonsai is under duress, your katsura might not always bear flowers and fruits.

Learn more about Katsura bonsai

The key to making your Kastura tree a great bonsai is in the watering. As a bonsai, the root system is always a bit too small for comfort. Kastura is usually very vulnerable to lack of water, even when not grown as a bonsai.

  • The typical response to lack of water is immediate shedding of all the leaves.
  • Don’t fear, your bonsai won’t have died!
  • Water again and new leaves will appear.

Learn to strike the right balance. You shouldn’t water too much, as this would trigger too much vegetation, but you shouldn’t also let it dry out too often!

Defoliation thus occurs rather naturally for Cercidiphyllum bonsai. In other bonsai species, it’s something occasionally forced on the tree to weaken it and make leaves smaller.

Best varieties for Katsura bonsai growing

All the katsura varieties can be coaxed into a bonsai, but the Cercidiphyllum magnificum are naturally smaller and slower-growing. They’re a better choice, but don’t let anything stop you from trying out a Cercidiphyllum japonicum bonsai!

  • Katsura typically has a rather shallow root system. This makes it very adequate for bonsai-growing compared to deep-root trees.

Smart tip about Katsura bonsai

Katsura is especially beautiful in fall. Keep it in a shaded place during the rest of the year, but bring it out to shine when the leaves start turning golden pink!


Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Cercidiphyllum bonsai by F. D. Richards under © CC BY-SA 2.0