I began to describe the steps required to grow Japanese black pine bonsai from seed last year, but left off just after planting the seeds. I ended up abandoning last year’s batch as only a dozen seeds sprouted. I tried again this year with much better luck. Due to a cold spring, the seeds took a long time to sprout. After maybe three months, most of the seeds I’d planted were growing well. It was time to make seedling cuttings.
Young pine seedlings
Pine seedlings typically produce a single tap root that reaches downward and grows vigorously to provide a good anchor for the tree. Although they are good for forest trees, tap roots are not as good for young bonsai.
A couple of generations ago, bonsai enthusiasts figured out that cutting the tap root produced a number of lateral roots. As these lateral roots developed, the young trees grew faster, denser, and produced a flared trunk base that is often desired in pine bonsai. Many pine bonsai have been produced in Japan by this technique, and the technique has been gaining popularity in the US for at least 20 years. I first learned about the process from Boon Manakitivipart and Bonsai Today numbers 12 and 20. The techniques below represent knowledge I’ve picked up from Boon, Bonsai Today, and many years of practice – I started my first batch of pine seedlings over 17 years ago.
The basics of the process are simple: make cuttings out of young pine seedlings. I begin by filling a nursery flat with 4″ plastic pots and adding the soil, one layer at a time.
25 pots in a flat
Drainage – large lava particles
Standard Boon mix – akadama, pumice, and lava
I will plant the pines in a pocket of sand to keep the cuttings moist. I watered the soil and then used the handle of a bonsai trowel to create craters into which I poured fine sand.
Repurposing a bonsai trowel
Craters filled with sand
Once the sand was in place, I again watered the soil and created small holes with large gauge copper wire. When the cuttings are ready, I’ll carefully drop them in these holes.
Creating space for the cuttings
The next step is creating the cuttings. I begin by carefully uprooting one cutting at a time. I try to use seedlings that are healthy like the one on the right in the photo below. The two seedlings on the left are weak – I did not use them for cuttings.
Two weak seedlings and one healthy seedling
Healthy pine seedling
There was considerable variation among the uprooted seedlings. Although I typically worked with one at a time, I did a few at once for this photo.
Pine seedlings – time to make the cuttings
I made the cuttings with a razor, leaving about 3/4″ of stem below the first needles. After making the cut, I quickly dropped the plants into water to keep them moist.
The seedling becomes a cutting
Plenty of seedling cuttings
Before planting the cuttings, I dip them in powdered root hormone to help the cuttings develop roots.
Seedling cutting with root hormone
I approach the planting of the cuttings with care. After setting the cutting in one of the holes I created, I gently pressed on the surrounding sand to close the gap. I tried to move the cutting as little as possible to avoid disturbing the hormone. I also skipped on water when I was done to avoid washing the hormone away.
Seedling cutting in its new home
The first flat complete
I’ve kept the seedlings outside under shade cloth for the past five weeks. I’m slowly moving them into spots where they get more light, and I’m misting them several times a day – more when it’s hot, less when it’s cool out. That’s the recipe for the time being. Once the seedlings start growing quickly – evidence of new roots – I can begin to fertilize and continue to provide the seedlings with more and more light.