Pruning

Both Scots Pine and Mugo Pine are single-flush pine bonsai.  Allow the new candles to emerge in Spring through to early Summer.  As the white sheaths at the base of each new needle begin to naturally shed (typically by early to mid-June in the northern hemisphere), cut back each candle to an even length across the entire bonsai.  Be sure, though, to leave some of the new needles from this year on each candle, as removing the entire candle can cause the branch to die back.  If, however, the new candle growth is exceptionally short, it may not be necessary to cut the candles back at all.  This is particularly true with Mugo Pine.

Heavy pruning on these European pine species is best done in the late Summer through Fall, from late August through October.  By pruning unnecessary branches and plucking old needles at this time of year, it is possible to induce back-budding, or adventitious buds, on pine bonsai.

For a more in-depth look at pruning techniques, please consider joining our online bonsai learning platform Bonsai-U!

Wiring and Styling

Wiring and styling pine bonsai is best performed in the late Summer through Fall.  During this period, back-budding can be induced by bending and shaping the branches.  Avoid wiring and styling pine bonsai in the Spring through the Summer, as this is when the new buds and candles are forming, which can easily be damaged.

Repotting

Repotting Scots and Mugo Pine bonsai is best done in Spring just as the buds begin to swell.  This usually happens sometime in March in the northern hemisphere.  When repotting, do not remove all of the original soil, but rather leave a core of older soil beneath the trunk to preserve the health of the bonsai.  Avoid cutting too many roots as well, as this can weaken the pine bonsai in the subsequent growing season.

Use a free-draining soil medium, such as Aoki Blend or a mixture of akadama, lava rock and pumice in a ratio of 1:1:1.  The soil particle size should be approximately 3/16 inch (4mm) for medium and large trees, and slightly small for shohin size bonsai.

Watering

The watering needs of pine bonsai will vary from species to species.  However, as a general guideline, check the water twice per day during the growing season from early Spring through late Fall.  Most pine bonsai will need to be watered at least once per day, and sometimes twice per day, during this period.  Water as the soil surface becomes dry.  In the winter months, check once per day and water as needed, which could be as little as once every 3-5 days depending on the climate and the individual pine bonsai.  For newly collected Scots and Mugo Pines, watering may need to be done much less frequently, even in the growing season, so as to avoid causing root rot.

Fertilization

For young Scots and Mugo Pine bonsai, fertilize from early Spring through late Fall using an organic fertilizer cake, such as Biogold or Tamahi.  This might cause the needles to elongate; however, the goal with a young bonsai is to produce rapid growth and thickening.  The needle size can be reduced at a later time.

For older, refined single-flush pine bonsai, do not fertilize until the new growth has completely hardened off.  This typically occurs in mid to late Summer.  At that time, begin fertilizing with the same organic fertilizer through late Fall.

Placement

Place pine bonsai in full sun year-round.  If you live in a hot climate, however, make sure to protect high-elevation pine species from the heat by placing them in afternoon shade.  For example, Scots Pine from the high elevation Pyrenees and Mugo Pine from higher elevation mountainous regions are best protected from the hot afternoon sun.

Pests/Diseases

Pine bonsai are susceptible to a number of pests including aphids, borers, caterpillars, mealybugs and weevils.  The most common diseases that affect pines are tip blight, needlecast and rust.  For a comprehensive understanding of what fungicides and pesticides to use on your pine bonsai, please join Bonsai-U!