What is Oak Bonsai & Care GuideLearn all about Oak Bonsai Trees and how to take care of them.
|Description||The genus Quercus consists of hundreds of oak species. Many are not suited to the art of bonsai. The ones that are suitable are much prized for two particular characteristics: Their awe-inspiring tree trunks and their rough, heavily-textured bark that suggests great age.|
|Position||Oak trees require full, direct sun. However, in areas where summers are hot and dry, the trees should be grown where filtered afternoon sun is provided.|
|Watering||Water the tree as needed to keep the soil moist. Do not allow the soil to become dried out.|
|Feeding||In their growing season, feed oak bonsai trees with a balanced liquid fertilizer at half-strength every two weeks. A fertilizer with high nitrogen concentration may be used if the goal is to develop trees with thick trunks. There are no guarantees as to whether a bonsai oak tree will produce acorns or not.|
|Leaf and Branch Pruning||Pruning is best carried out in early spring when the tree burst into vigorous growth, sending out rather elongated shoots. Unwanted/undesired shoots should be cut away immediately.|
|Re-potting & Growing Medium||Re-pot every year in early spring. Roots should only be pruned in the spring before new growth emerges, and this should be done at the time of re-potting. The roots should be pruned only minimally. It is imperative that the roots are not pruned at any other time of the year. Oak trees are ideally grown in soil that is comprised of roughly 60 percent aggregates and 40 percent organic matter. Native North American oaks are adapted to many different soil conditions, and they will thrive in any soil that is suited to the growing of bonsai trees.|
|Wiring||Most oak trees are highly responsive to wiring, especially the pin oak. Any wiring that is undertaken must be done gently so as not to cause damage to the bark, however. The tree is best trained into the formal or informal upright style, but the use of gentle wiring can create cascade styles as well. The tree also looks wonderful when it is trained as a multi-trunk specimen.|
|Notes||There is only one species of oak that is indigenous to Japan, and it is mainly used in the manufacture of drums. As such, oak trees are not generally used in the art of bonsai in Japan. The use and popularity of oak trees as bonsai subjects gained traction during the 1950s in California.|
There are hundreds of members of the Quercus genus, that which contains all of the oaks. There are more than 600 species native to North America alone. Not all of these are amenable to being grown as bonsai. Those that are, however, make lovely and gratifying bonsai subjects. Oaks are more particular than other plants about when the grower prunes their roots. Oaks demand greater care in that regard than popular maples and conifers.
Oaks As Bonsai Subjects
Some oaks offer the qualities that bonsai artists and growers most want to achieve. Two of these characteristics include predisposition to form impressive trunks and their rough-textured bark that conveys an image of age. Only one oak is native to Japan, however, and that species traditionally has been a utility tree used to make drums. Oaks have not been traditional bonsai subjects in Japan, but they began gaining popularity in California in the 1950s.
The Southern live oak, Quercus virginiana, is one of the most popular evergreen oaks for bonsai. There are other live oaks native to the Western states of the United States, but the Southern live oak often is more widely available. Live oak species are called “live” because, in their native habitats, they are not deciduous but stay green all year. Q. virginiana is native to the Southern Atlantic coast and all along the Gulf coast. Its leaves are narrowly elliptical to narrowly oval, with smooth margins. The leaves are heavy and dark green, providing pleasing bonsai foliage. Leaves of live oak species native to the Western United States are similar. Though Q. virginiana is the most widely used of all of the live oaks commonly used in bonsai, any of the live oak species native to North America are appropriate for bonsai use.
Among the deciduous oaks, likely the pin oak, Quercus palustris, and the Northern pin oak, Quercus ellipsoidalis, are the most accommodating for the bonsai artist. The pin oak has deeply lobed, toothed and pointed leaves, with deep, irregular sinuses extending nearly to the midrib of the leaf. Pin oaks also have leaves that are somewhat smaller than some other oaks, lending themselves well to being miniaturized through bonsai culture. Q. palustris is native to much of the Eastern portion of the United States and adapts well to a wide range of growing conditions.
The growing medium of any oak species should be about 40 percent organic material and 60 percent aggregate or nonorganic substrate. As oaks native to North America grow in all types of local environments, they are quite adaptable to common bonsai growing media.
This is the area in which oaks present oak-specific challenges in bonsai culture. Whereas the bonsai artist or grower can root prune a maple or pine virtually at any point in the growing season, oaks are much more particular about the timing of root pruning. Root pruning should be done only in the early spring, after the oak breaks its winter dormancy but before it has gathered much new growth. Missing the annual root pruning altogether is better for an oak bonsai than imposing root pruning at the wrong time of year.
Virtually all bonsai oaks will need supplemental fertilization during the growing season. As there are no ornamental flowers that the grower would desire, there is less need to withhold nitrogen as is the case with flowering bonsai. Heavier nitrogen fertilization may be desirable in those plants that the grower is trying to coax into developing heavier trunks, but oaks respond well to a weak solution of balanced fertilizer that addresses both top- and root-growth needs. Bonsai oaks may or may not produce bonsai-sized acorns.
Various live oaks, pin oaks and others respond well to wiring and training. Most oaks are best suited for training into formal upright styles and do less well with windswept or cascading styles. Other than the formal upright style, oaks are well suited for multi-trunk training and for forest bonsai growing.
Oak bonsai plants not only tolerate full sun better than many other bonsai plants, they also need a good bit of direct, full sun, preferably in the form of morning sun that is not so hot and drying during the summer. During hot afternoon hours, oak bonsai need to have filtered sun to full shade. The sunlight is critical, however. When sited in full shade at all times, oak bonsai often develops dieback or may develop abnormally large leaves. These large leaves are inconsistent with the goal of bonsai, of course. They signal the grower that the plant needs more sunlight than it is getting.
Pruning & Shaping
Oaks are known for throwing long shoots after emerging from winter dormancy. These shoots can contain seven or eight nodes, which can be spaced rather far apart if the plant does not receive sufficient sun during the day. The grower will need to stay on top of this early growth, because any shoot that the grower does not see as being an integral part of the plant structure in the future will need to be removed right away.
The shaping method preferred for an oak bonsai largely depends on the species. Though the Mediterranean Cork oak responds best to pruning, the pin oak is more suited to wiring. Regardless of species, any oak being wire trained needs to be wired gently. Gentle wiring avoids damaging the bark that can be quite heavy and striated on some species. On other species, gentle wiring avoids breaking branches that can become brittle. Recalling how native oaks respond to ice storms or other similar assaults on their branches can help to guide the grower to use wiring very gently. Some of the live oaks – specifically the Coast live oak native to California – can be bent easily with wiring. Other oaks are less willing to be bent into formal bonsai styles. As is the case with any bonsai subject, the grower will do well to observe full size, native forms in their natural habitats. Those oaks that grow well in the face of coastal winds likely will be most accommodating of wiring into windswept or cascade styles.
Some of the very large-leafed oak species such as Southern red oak may be less successful as bonsai subjects, but there are several Quercus species that lend themselves quite well to bonsai. Oaks are strong and resilient and they are long lived. Though oaks have some narrow requirements such as early spring root pruning, they are quite rewarding as bonsai subjects.