Back in July I treated a number of black and red pines for suspected root aphids (see “Why are my trees yellow“). I’ve noticed a few changes since then and wanted to share what I’ve seen.
- Some yellow growth has turned green
- The healthiest trees are sending out summer shoots
- The weakest trees remain unchanged
My biggest worry when drenching the two- and three-year old pines was that the treatments would damage roots. Although it’s far too early to tell, I can report that there has been no evidence to suggest catastrophic changes to the trees that were treated. On a more positive note, I’ve noticed a few trees turn from yellow to green. The new needles on the pine below were yellow before treatment. Although the old needles remain yellowish, the new needles have greened up considerably.
3-1/2 year-old black pine
I have no way to tell whether or not the greening resulted from any treatment, but I’m happy nonetheless as it’s a sign of the tree’s health.
Some of the healthiest trees are now sending out summer shoots.
Summer shoots on 2-1/2 year-old black pine
We often think of black and red pines as trees that send out new growth one time per year – two when we decandle – but healthy pines regularly send out summer shoots when they’re growing vigorously. This is particularly true of younger pines.
1-1/2 year-old black pine
1-1/2 year-old red pine with summer shoots
Pulling a flat out at random, I noticed that all but one of the trees had summer shoots.
1-1/2 year-old pines
These trees will all need wiring and repotting before next spring. In the meantime, I’ll continue to feed heavily to help the trees prepare for winter.
Decandling and cutback are great techniques for redirecting growth on black pines. Here are some examples. Tree #1 After eleven years, the trunk of the tree below has reached the desired size. Any further significant growth and the curves would begin to disappear. The goal for this stage of development is to reduce investment in the sacrifice branch and further refine the lower branches.
11 year-old black pine
Close-up of the lower branches
Tree #2 The goal for the tree below is to generate more branches low on the trunk. The escape branch helped the tree reach its current size, but further growth is not necessary as the trunk is now the desired size.
11 year-old pine
After decandling and cutback
Tree #3 The tree below is another future shohin black pine. I’d like the right side to continue to thicken so I left the right hand escape branch in place while reducing the escape branch on the left. I decandled most of the lower branches to encourage new buds close to the trunk.
11 year-old black pine
After decandling and cutback
The challenge here is getting summer buds to develop when the escape branch remains strong. I’ve experimented with this in the past and found that it’s not always easy to generate summer buds without further reducing the escape branch. I’ll find out in fall what happens with this tree. Tree #4 The tree below is slightly further along as the escape branches were removed last year. The goal is to replace vigorous spring growth with more refined summer growth. I decandled all spring shoots and removed extra needles.
11 year-old black pine
After removing extra needles
The steps are simple. 1) Remove spring shoots.
Shohin black pine – 21 years old
After removing spring shoots
2) Remove extra needles.
After removing extra needles
3) Perform light cutback as needed.
The first branch on the right is long
After shortening the first branch on the right
That’s it. In all I removed 14 branches, lots of needles, and 212 spring shoots.
Spring shoots removed
I decandled on the early side as I’d like the tree to be show ready by the end of September. I’m also feeding the tree more than usual to further boost the summer growth.
Effect of hormone treatments on P. thunbergii cuttings for the production of surface roots on trees cultivated for bonsai
Pinus thunbergii is a popular species of conifer cultivated as bonsai. In an effort to produce superior surface roots on P. thunbergii, bonsai enthusiasts have developed a method of making cuttings from young seedlings to replace any taproots with radially distributed lateral roots. These lateral roots are developed to improve the look of the tree when it matures and to help develop taper or flair near the base of the trunk. The focus of the present study is to measure the effect of different treatments on the production of roots developed through the “seedling-cutting” technique.
Cuttings were made from 63 seedlings of P. thunbergii planted 84 days previously. Treatments tested include 1-Naphthaleneacetic acid (Dip ‘n Grow), 1-Naphthaleneacetamide (Rootone) and a low dose fertilizer (Olivia’s Cloning Gel).
Root treatments outperformed controls by a small margin when product instructions were followed. Increased exposure to hormones stimulated increased root production.
Bonsai enthusiasts appreciate Japanese black pines, Pinus thunbergii, for the age and character conveyed through their bark as much as for their general shape and appearance. A pine’s surface roots play an important role by demonstrating the tree’s connection to the ground in which it grows.
As black pine bonsai became more popular, producers developed approaches to creating trees with superior surface roots. By making a cutting of a young seedling, a grower can essentially replace the taproot with several lateral roots that are distributed radially. This approach has become known as the “seedling-cutting” technique.
The idea behind the present study is to guide the production of pines created by the seedling-cutting technique. While seedling-cuttings can be developed without the use of hormones, their application can produce significantly more roots than seedling-cuttings made without them.
This study is limited to the comparison of basic approaches to creating seedling-cuttings and does not allow for specific recommendations for producing superior roots. It is intended as preliminary research aimed at guiding future efforts to optimize root production for bonsai in P. thunbergii and Pinus densiflora.
Materials and Methods
Creating the Seedling-Cuttings
P. thunbergii seeds were sown in a bed containing equal parts of lava, pumice and clay pebbles (particle size was between 1mm – 5mm) and covered with a thin layer of sand (particle size 1mm – 2mm) on February 9, 2013. After 84 days the seedlings were uprooted and the taproots were removed with a razor blade leaving approximately 2.5cm of stem. The cut is made with a slicing action to avoid crushing stem tissue. Cuttings were placed in water after the taproots were removed to prevent them from drying out.
Figure 1. P. thunbergii seedlings 84 days after planting in seedbed of lava, pumice and clay pebbles covered with thin layer of sand. The red-colored stems indicate optimal time for making seedling-cuttings.
Figure 2. Seedling-cutting.
Dip ‘n Grow Treatment: Cuttings were placed in a vial with Dip ‘n Grow (1-Naphthaleneacetic acid 0.05%) for 5 seconds per the manufacturer’s instructions. A second batch remained in the vial for 5 minutes to measure the effect of increased exposure.
Figure 3. Seedling-cutting to be dipped in Dip ‘n Grow.
Rootone Treatment: Cuttings were dipped in Rootone (1-Naphthaleneacetamide 0.2%) and excess powder was flicked off.
Figure 6. After flicking off excess hormone.
Olivia’s Cloning Gel Treatment: Cuttings were dipped in gel (N-P-K: 0.08-0.15-0.09) before planting.
Figure 7. Seedling-cuttings in cloning gel.
Control: Cuttings were planted with no hormone or other treatments.
Cutting at the First Root: A variation of the control, these seedlings were cut below the first root. Taproots were removed leaving a single lateral root.
Figure 8. Removing taproot below first lateral root.
Planting the Seedling-Cuttings
Cuttings were planted in a bed of lava, pumice and clay pebbles similar to the bed used for germination. Instead of sand, channels of small clay pebbles (particle size 1mm – 2mm) were used to provide additional moisture for the cuttings.
Figure 9. Planting medium used to grow seedling-cuttings.
The bed was watered before planting and perforations were made with a 2.5mm wire. Treated cuttings were placed in these perforations and sand was added to hold the cuttings in place. Sections of 1.5mm aluminum wire were used to pin down cutting foliage to prevent the cuttings from moving during watering. Seedling-cuttings were kept outdoors under 30% shade cloth and watered when the planting medium began to dry out.
Figure 11. After planting, the 63 seedling-cuttings were gently watered.
Results and Discussion
The seedling-cuttings were watered regularly throughout summer, fall and winter. In winter, some seedlings showed signs of yellowing, a sign of stress due to temperature, growing conditions, fungus and/or infestation. Seedling-cuttings were uprooted 295 days after planting when the apical buds began to extend.
Figure 12. Seedling-cuttings 295 days after planting, February 23, 2014.
Mortality was low overall (6.3%) but significantly higher among the control and cut to one root seedling-cuttings (25%) than among the treatment group (3.6%). As mortality could be attributed to bird activity as well as cutting treatment, mortality was not considered as a factor contributing to study results.
The seedling-cuttings were evaluated by counting primary root divisions. Results for the control group and the group cut back to a single lateral root showed no difference, each producing 2-3 lateral roots per seedling-cutting. The cloning gel performed slightly better than the control, whereas the hormone treatments produced better results. The treatment that produced the greatest number of roots was the group that soaked in the Dip ‘n Grow solution for 5 minutes, 60 times the recommended exposure.
The reason for taking two approaches to the Dip ‘n Grow treatment is that it offered the best flexibility in terms of managing exposure to the cutting treatment. Holding a stem in powder longer does not allow for greater hormone absorption. Exposure to gel nutrients remains the same regardless of time spent in the gel as it sticks to the stem after it is removed. Stem tissue has some ability to absorb liquid hormone as demonstrated by the increased root production resulting from increased exposure to the liquid Dip ‘n Grow.
Figure 14. Average number of roots per seedling-cutting. Range indicates minimum and maximum values.
This study suggests that varying the time spent in a liquid hormone solution may provide some flexibility for controlling root production. Producers wanting more surface roots could increase exposure to hormones while producers wanting fewer could limit exposure. Further study is required to determine expectations for root production based on varying levels of hormone exposure.
Directions for Further Study
In addition to suggesting a correlation between hormone exposure and root production, this study shows that a variety of approaches can produce seedling-cuttings acceptable for use as bonsai. Further inquiries could add to these findings by:
- Measuring the effect of increased exposure to hormones to offer guidance relating root production to exposure time. This would allow growers to control root production to fit their needs.
- Measuring the effect on stem length for the cutting. Does leaving longer or shorter stems make an appreciable difference?
- Varying the time at which seedling-cuttings are made.
- Modifying the planting environment to ensure all seedling-cuttings receive equal warmth and moisture. Planting all seedling-cuttings in one containers makes the amount of light received equal but cuttings planted near the sides of the container receive more warmth and dry out more quickly whereas cuttings towards the center of the pot have more moisture available to them.
- Measuring overall root mass and/or plant mass to determine which approach leads to the most vigorous trees.
- Varying the timing and types of fertilizer applied during the growing season.
- Varying the growing medium and/or exposure to sunlight to determine optimal conditions for increasing vigor.
- Determining the optimal number of surface roots for trees of different styles and sizes. This is a broader and more subjective area of inquiry that is tied more closely to the fundamental purpose of creating bonsai as objects for aesthetic appreciation.
|Roots per Seedling-Cutting|
|Dip N Grow 5 minutes (n=7)||4||12||6.3|
|Dip N Grow 5 seconds (n=16)||2||8||3.9|
|Olivia’s Cloning Gel (n=15)||2||5||3.0|
|Cut to one root (n=3)||2||3||2.7|
Table S1. Low, high and average number of roots per seedling-cutting.
Figure S3. Control specimen.
|Roots per cutting|
|Dip ‘n Grow – 5 seconds (n=16)||2||5||5||2||5||3||4||3||8||3||2||3||6||5||4||3|
|Olivia’s Cloning Gel (n=15)||2||3||2||5||3||1||3||3||3||2||4||3||4||2||5||x|
|Cut to one root (n=3)||3||3||2||x|
|Dip ‘n Grow – 5 minutes (n=7)||7||4||6||5||12||5||5|
Table S2. Number of primary root divisions for seedling-cuttings observed 295 days after cuttings were made. “x” indicates seedling-cuttings that died or disappeared.
Acknowledgements: The author wishes to thank Boon Manakitivipart and Kathy Shaner for introducing him to the seedling-cutting technique as well as Kindai Bonsai and Bonsai Today for publishing articles on the topic.
Author Contributions: Conceived and designed the experiments: JD. Performed the experiments: JD. Analyzed the data: JD. Wrote the manuscript: JD.
Keywords: Conifers, Hormones, Horticulture, Lateral roots, Plant roots, Seedlings
Citation: Dupuich J (2015) Effect of hormone treatments on P. thunbergii cuttings for the production of surface roots on trees cultivated for bonsai. Bonsai Tonight. http://bonsaitonight.com/2015/07/17/effect-of-hormone-treatments-on-p-thunbergii-cuttings-for-the-production-of-surface-roots-on-trees-cultivated-for-bonsai/
Funding: This research was funded by the author.
Competing Interests: The author has declared that no competing interests exist.
Copyright: © 2015 Dupuich. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.