In this instructional video, Harry Harrington demonstrates a comprehensive approach to developing Japanese black pine (Pinus thunbergii) seedlings and saplings into robust bonsai with thick trunks. He begins by explaining the scarcity of the species in the UK market and the need to start from cuttings or seeds. The video walks through the process of lifting the trees in their pots, amending the substrate with pumice and akadama, and establishing a bonsai structure early on. Harrington emphasizes the use of a sacrificial leader at the top of the tree to bulk up the trunk while developing the lower branches for the final design. He introduces wiring techniques that both shape the trunk and, when left in place, promote rapid trunk swelling by cutting into live veins. The presenter details how to manage wire removal safely, including using Vaseline to prevent bark damage. He stresses the importance of maintaining temperatures above 12 °C, providing ample light, humidity, and heavy watering, and feeding with organic fertilizers, seaweed, and fish emulsion to accelerate growth. Seasonal strategies such as using cold frames or polytunnels to extend the growing season are discussed. Harrington also outlines optimal timing for repotting (August to mid‑October) and for pruning and wiring (late summer to October) to avoid frost damage. Throughout, he showcases several case studies of pine saplings, illustrating the sacrificial leader method, coiled‑wire thickening, and long‑term development over decades. The video concludes with a call to like and subscribe.
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Japanese black pine, or Pinus thunbergii, is a classic species for bonsai that hasn't been available to the UK market for some time now. The only way to obtain one is to buy an older and therefore more expensive bonsai, or to start a few from cuttings or seeds. So if you've obtained some Japanese black pine seedlings or saplings, I want to develop them into bonsai. What do you do? Just let them grow. In this video, I'm hoping to show you how to approach the development of these pine saplings and pines in general, plus a few tricks to help fatten them up fast. These are Japanese black pine grown from cuttings. Over 3 years and are very well rooted. Having been candle pruned in midsummer to encourage better ramification, they are currently extending a second flush of growth, something that isn't so easy to do here in the UK. Unfortunately, we don't have the temperatures or the light or length of summer for multiple flushes on Japanese black pine. These trees are very well rooted with plenty of healthy mycelium growing in the substrate. Today I'm lifting the black pines higher up in their pots, adding a little pumice to the base and some akadama and pumice mix around the root ball. This will give the roots fresh soil to grow into. The major difference with thickening pines from deciduous trees is that from early on you need to establish what will be the branches of the tree, as back budding from a fully formed, bare, mature trunk is very difficult. Build a small bonsai structure now at the base of the trunk, but allow a sacrificial leader at the top of the tree to grow hard to bulk up the trunk overall. This sacrifice can continue to grow for years if necessary until you are satisfied with the girth of the trunk. To avoid a straight trunk when the tree has thickened up, add some movement now by applying wire to the sapling. Exaggerate the bends as the trunk will straighten them out a little as it thickens up over the Twist and bend the trunk in the same direction as you have wired. This will tighten the wire around the trunk. So you apply the wire clockwise, twist the trunk clockwise. The wire will take a year or so to hold the trunk into its new position, when it can then be removed. One useful technique available to us growing pines is to leave the wire permanently on the trunk. As the wire cuts into the swelling trunk, it causes the live veins either side of the wire to swell considerably, thickening the trunk twice as fast as without. This Austrian black pine, Pinus nigra, is an example of coiling and swelling of the trunk of a pine sapling, creating a much thicker trunk in The cold wire cutting in also causes the live veins to spiral around the trunk instead of straight upwards. If you really want to cut the wire in the future after it has started cutting into the trunk, be aware that uncoiling the wire can pull away the bark and the cambium. You can try rubbing Vaseline onto the wire and letting it soak in, and then trying to remove it 2 to 3 months later. This tends to avoid the bark sticking to the wire. Incidentally, this technique also works when removing deeply embedded wire on branches or any part of a bonsai. This Scots pine from Poland was field grown with coiled wire giving it movement and helping to thicken the trunk. It has caused it live veins, around the trunk. I'm currently creating a shari from the coils, a process that has taken a couple of years. One important thing to do when you're trying to bulk up your tree is keep feeding hard and keep the tree over 12 degrees centigrade for as long as possible. 12 degrees centigrade seems to be the point below which the tree will stop growing. So to exaggerate and lengthen your season, if you have the use of a cold frame or a polytunnel in the early spring or the autumn, you can extend the growth time of a Japanese black pine. The second example of work on a Japanese black pine sapling shows me building a small bonsai structure now with the aim of allowing a sacrificial leader at the top of the tree to grow hard build up the trunk. This sacrifice can continue to grow for years if necessary. The branches at the base can be developed for the actual finished bonsai, should be given plenty of light to encourage growth, but it should also have short internodes created by either pinching out the very tips of new candles if they extend too far, or cut back entirely in late summer. With the trunk given some shape using cold wire, you can see the beginnings of a branch structure and also a new leader ready for the tree as a bonsai when the upper sacrificial growth has thickened the trunk. This next example Japanese black pine is one I purchased 3 years ago with its sacrifice leader still in place, but with nicely developed branches still at the base ready to be wired and styled. As already mentioned, Japanese black pine enjoy high temperatures in general and plenty of humidity as well as sunlight. They are a relatively thirsty pine species and can be watered much harder than Scots and particularly white pine bonsai. Feed with plenty of organic fertilizer, seaweed, and fish emulsion for maximum growth. Sacrificial branches can also be used to bulk up parts of the trunk. Look at this example of a relatively short Japanese black pine with a huge sacrificial branch used to thicken its base. I took these images a couple of years ago when removing the, the sacrifice branch for the owner in stages. Lastly, some words about timing while I show a magnificent Japanese black pine developed by enthusiast John Golding of over 2 decades. I've now owned the tree for 2 years and I'm refining the growth by increasing ramification and reducing needle size. The absolute best time for repotting pines of all types is from August, when the new needles have set, until mid-October. This is also the safest time to repot all pines. The best time for pruning and wiring pines is again after the new growth is set in late summer until October when the risk of frost first appear. I hope you've enjoyed this video. If you have, please like and subscribe to my channel.
