Scots pine bonsai

Placement

Scots pine is grown strictly outdoors, all year. In spring, summer, and autumn, give it as much sun as possible: full light keeps the needles short and the tree vigorous, while in shade the needles lengthen and poorly lit branches die back. It likes cool summers and suffers in humid heat: in a hot climate, make sure air moves freely around it.

In winter it needs a true cold rest of a few weeks between 32 °F and 45 °F: never bring it into a heated house. In the ground it is one of the hardiest trees there is, but in a pot its roots are exposed: when the root ball is frozen, shelter it from freezing winds.

Avoid leaving the foliage wet for long. Several needle and shoot diseases that are common on this species need damp needles to take hold.

Soil mix

Use a very free-draining, airy mix. A conifer mix of equal parts akadama, pumice, and lava rock works well. In a rainy climate, add more lava rock or grit; if you cannot check the watering often, a little more akadama holds more water.

In a good pine mix you will see white threads: they are a fungus partnered with the roots, very beneficial, and it needs air to live. Overall yellowing of the foliage often signals old, compacted mix in which the roots lack air; replace it gradually over several repottings.

Watering

There is no schedule: water thoroughly when the top layer of mix starts to dry. In midsummer that can mean every day or every other day; in winter, far less often. Pines hate sitting in soggy mix, but the root ball must never dry out completely. While the shoots are lengthening, shelter the tree from long spells of rain: too much water at that stage produces long needles. Deliberately holding back water to shorten the needles, on the other hand, is an unnecessary risk.

Feeding: a weakened tree can be fed as long as temperatures stay mild. For a healthy tree in refinement, the usual approach is a single low-nitrogen feeding in spring, then no fertilizer until the new needles have hardened in late summer; after that, a richer fertilizer every two to three weeks until early autumn builds vigor and encourages new buds. Avoid excess nitrogen, which makes tip blight worse.

Pruning

Scots pine produces only one flush of growth a year, so never remove all of its candles, which could kill it. From late spring to early summer, shorten elongated candles to an even length; where more than two candles grow from one point, keep two. In autumn, remove surplus shoots, keeping two lateral shoots of equal strength, heading in the right direction and forming a V. In the strongest areas, pluck old needles to balance growth.

Work slowly. Do not cut back more than half of a nursery pine’s top growth in one season. An old tree tolerates only one major intervention a year: after repotting, hard pruning, or heavy wiring, wait twelve months. Heavy structural pruning is done in late winter. Leave a stub, seal the cut with petroleum jelly, then the following year turn it into deadwood or remove it. Prune in dry weather with disinfected tools.

It suits every style except broom. Literati, with its long bare trunk, echoes its natural habit. The dwarf cultivars ‘Beuvronensis’ and ‘Watereri’, with their short needles, make excellent subjects.

Wiring

Wire from autumn to early spring, or just after shortening the candles, from early to midsummer. Harder annealed copper wire is best for pines; aluminum is easier for beginners. Use wire about one-third the thickness of the branch, wound at 45°, and wrap thick branches in damp raffia before bending them. Branches take a few months to hold their new position and swell around the wire within one to four months: check them often and remove the wire by cutting it at every turn. On an old tree, heavy wiring counts as the year’s major intervention.

Repotting

Two windows work: in spring, as the buds begin to move, or in late summer and early autumn, when the heat eases but roots still have time to regrow before winter. The second window is often considered better, because roots grow more after the shoots have finished extending. Once established, repot every three to five years. Never bare-root the tree: replace at most one-third, or half, of the mix, do not wash the roots, and keep some old mix to preserve the beneficial fungus. There is no need to prune the foliage to “balance” root pruning.

The species is sown outdoors in early spring, because its seeds need frost to germinate; cultivars are grafted in late winter. Watch for aphids, spider mites, scale, and sawfly larvae, which you can pick off by hand. Sudden discoloration followed by needle drop in spring points to a needle disease that is hard to cure. Stunted shoots with short brown needles and resin reveal tip blight: cut them out. A pine declines quickly once symptoms show, so seek advice without delay.