Picea bonsai are members of the large evergreen coniferous tree genus Picea (spruce) and the family Pinaceae (pine). The tree is native to the Northern Hemisphere (boreal and northern regions), where it is also popular as a Christmas tree. In their natural habitat, this tree can grow up to 60 meters tall, and typically has a lifespan of 40 to 60 years. However, the oldest spruce tree is believed to be over a thousand years old. It is found at lake Quinault, and has a girth of seventeen meters.
Mature trees develop a conical or pyramidal shape. The branches are whorled and bent downwards at the base, with tips slightly pointed upwards. The leaves are needle-shaped, have four sides, and remain on the tree for up to 10 years. The bark is scaling or flaking. The cones (flowers) hang downward, and the same tree contains both male and female cones.
Etymologically, the common name of this tree, spruce, dates back to the early 17th century and is of late middle English origin. The word means “something that originates from Prussia”. Interestingly, in the early 14th century, the word “spruce” was a generic name for a large range of luxury items imported to England, including wood and furniture.
Some of the most extraordinary Picea bonsai specimens belong to the European variety Picea abies (Norway spruce) and its cultivars. These incluce P. abies albertiana ‘conica,’ P. abies ‘Echiniformis,’ P. abies ‘Little Gem,’ P. abies ‘Nidiformis.’ P. abies ‘Pumila,’ P. abies ‘Pumila Nigra,’ P. abies ‘Pygmaea’ and P. abies ‘Variegata’.
Another popular specie of Picea bonsai is the North-American Picea engelmannii, also known as Blue Engelmann spruce. This specie is cherished for its camphor-smelling needles and lovely orange-color cones.
The best known Japanese Picea bonsai species are Picea jezoensis (Ezo spruce or Yeddo spruce) and Picea glehnii (Edo spruce, Sakhalin spruce, silver fir).
A commonly seen Picea bonsai in Canada is Picea mariana (black spruce), which can grow in weeping form or in a narrow form. In the USA, the most popular Picea bonsai is Picea pungens (blue spruce or “River Road”), which can thrive even at high altitudes.
This guide provides the foundations of Picea bonsai tree care.
How Long Does It Take to Grow Picea Bonsai?
Picea bonsai is one of the most popular types of bonsai trees. How long it takes to grow this bonsai tree depends on the species and the cultivar. On average, in its natural habitat, spruce trees typically grow from 30 to 60 cm per year. To get a well-developed Picea bonsai specimen requires at least 10–15 years, while in some cases it can take up to 30–60 years (for a mature and highly-prized bonsai tree).
How to Plant and Grow Picea Bonsai?
The Picea bonsai is propagated either from seeds of from late-summer cuttings.
In the case of propagation from seeds, the seeds are collected in autumn or winter, undergo a cold pre-treatment, and then they are planted in early spring. It has been reported that only a small percentage of the saplings survive the first season.
If propagation is done using cuttings, those cuttings need to be taken either at the start or at the end of the growing season (early spring or late autumn). The stem is pruned at an angle, and the needles are removed from the lower two-thirds of the cutting. This is a rather challenging method since it may take up to two years for the roots to appear.
The Picea bonsai requires exposure to full sun throughout the growing season. The plant thrives well in both direct and indirect exposure to light. However, it is recommend to avoid exposing the plant to noon light, since it can cause the foliage to turn brown.
To provide best care for the Picea bonsai during the winter season, the plant should be kept in semi-shade, to allow it to go through its dormant phase. It should also be ensured that the plant—particularly its roots—is protected from frost. Frozen roots can no longer provide water to the plant, resulting in quick drying out of the evergreen foliage.
Soil and Watering Needs
The Picea bonsai does not require specific pH value of the soil, and can grow well in neutral, acidic or alkaline soils which are rich in organic nutrients. Grainy soil is particularly recommended for young specimens, since it can provide good stability to the plant.
Picea bonsai needs regular and thorough watering. Two extreme conditions should be avoided—dry soil and overwatering. As soon as the soil begins to get dry, the bonsai plant should be watered, but its roots should never be kept soggy. Excess moisture of the soil can be a lead cause of fungal disease. During the cold months the amount of water should reduce, but the roots should never be left to dry out completely. A good practice in winter is misting the leaves and the surrounding air, as it prevents the foliage from drying out.
The Picea bonsai thrives well when fed with solid organic fertilizer once a month. During the main growing season, a weekly application of liquid fertilizer is also recommended. When the tree is treated with chelates, nitrogen and iron-rich spray fertilizer, it develops a rich and attractive dark-green foliage. During the winter no fertilizer should be applied, since the plant is in its dormant (sleeping) phase.
How to Care for Your Picea Bonsai?
When it comes to Picea bonsai trees, most of the traditional bonsai stiles can be used. However, the most challenging styles (recommended only for experienced bonsai enthusiasts and professionals) are the informal and formal upright styles. Most commonly used styles are cascading, root-over-rock, slanted and windswept.
Pruning, Pinching and Wiring
While pruning a Picea bonsai, it is important to keep in mind that this tree does not back-bud from old wood. Therefore, bonsai experts advise against removing all the buds and needles from any of the branches, leaving it bare. A good practice is to pinch young shoots in spring, as they are soft.
Typically, several branches of the Picea bonsai tree simultaneously grow and reach the same height. A nicely shaped Picea bonsai will have only one branch of a whorl in the lower part of the tree. To prune back a longer branch, that branch should be cut to small stump, close to the trunk. Cutting the branch all the way to the trunk can result in a serious damage to the structure of the tree.
Wiring is best performed at the beginning or at the end of the growing season (in early spring or late summer). Wiring done in summer world be a serious mistake, as it can result in a dieback. Wiring of the Picea bonsai tree requires patience and perseverance. Namely, the tree has very flexible branches which easily bend, but they also quickly bounce back to their old positions. As a result, the branches can be twisted quite easily without a worry that they might crack, but wiring needs to be done repeatedly, over a longer period of time. In the case of mature branches, it may take up to several years for them to set into a new position. While the branches are flexible, it is the needles that need special attention while wiring, so that no excess damage happens to the foliage. It is recommended to use thin wiring material.
It is recommended to repot a Picea bonsai biannually, especially when they are still young. Older and mature trees can be repotted once in four to five years, or sometimes at even lower frequency, since older trees have slower growth. The best time of the year to repot a Picea bonsai tree is early spring, before the new sprouts appear or, alternatively, late autumn.
Picea bonsai species does not tolerate massive loss of the root mass, so root pruning should be done carefully and in moderation. No more than a third of the roots should be removed at once, regardless whether it is a youngling or an adult bonsai tree. The roots form a large ball, and therefore it is recommended to use a deeper pot than the one typically used for repotting other bonsai species. It is recommended to use a standard soil mix which contains structurally stable grains and can drain well. After repotting, the tree should be protected from exposure to full sun.
Pests and Diseases
The Picea bonsai is vulnerable to various pests, most notably to green spruce aphids, spider mates, budworms (especially in the Northern Hemisphere), needle miners, cytospora cankers, and caterpillars. Furthermore, fungal diseases, such as needle cast and rust can also attack the bonsai. It is thus important to take a good care of the Picea bonsai tree by regularly applying a specific pesticide. Intervention is required as soon as any pest or disease is noticed on the plant. Spruce budworms can easily be removed by hand. Growing a Picea bonsai tree indoors is a commonly used strategy to prevent or minimize the occurrence of various pests and diseases.