Pruning

Pruning both Spruce and Fir species is quite a simple process.  In spring, allow the new shoots to elongate to 0.5-1.5 inches (1-2.5 cm) long.  Once the shoots reach said length, either pinch or cut each shoot back to an average length across the tree to balance energy.  Within a few weeks, a new terminal bud will appear at the end of the cut shoot, and back buds will likely appear further down the shoot as well.  These species will likely only produce one flush of growth per year, so you will only need to prune the shoots once in a growing season.

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 these species is best done in fall or late winter before the new shoots start to swell.  Avoid styling in the coldest part of winter if you plan to perform heavy bending and manipulation of the branches.  Detail wiring and light bending can be done at any time of year, but fall or late winter are optimal.

Repotting

Repotting spruce and fir bonsai is best done in early 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 often cause the tree to weaken 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

As a general guideline, check the water twice per day during the growing season from early Spring through late Fall.  Most spruce and fir bonsai will need to be watered once per day, and sometimes twice per day, during this period.  Keep in mind that these species do better if kept slightly on the dry side, but make sure  to 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 bonsai.

Fertilization

Fertilizing spruce and fir bonsai will be dependent on the stage of development of the tree.  For example, younger trees are best fertilized with a high-nitrogen synthetic fertilizer to rapidly increase their size and vigor.  Older, more refined spruce and fir bonsai should be fertilized with a milder organic fertilizer with a lower nitrogen value.  All spruces and firs, though, regardless of development, should be fertilized from the early growing season through late Fall.

Placement

As these species are high elevation plants, they can take direct sun year round.  However, if you live in a hot climate, consider putting them under shade cloth or in a shady location during the hottest summer months.  This is particularly true when dealing with extreme high-elevation species such as Engelmann Spruce and Subalpine Fir.

Pests/Diseases

Spruce and Fir bonsai are susceptible to a number of pests including bagworm, balsam twig aphid, bark beetles, Cooley spruce gall adelgid, eastern spruce gall adelgid, gypsy moth, spruce bud scale, spruce spider mite, and white pine weevil.  The most common diseases that affect spruce and fir are canker, rust, needle cast and blight.  For a comprehensive understanding of what fungicides and pesticides to use on your spruce and fir bonsai, please join Bonsai-U!