A pine needs attention in order to succeed the growing of this specimen.
Though Pines are growing in a variety of climates, it is important two understand their needs as bonsais. This is a general description and guideline to take care of the Pines as bonsais. Please remark that attention must be taken into the fact that different species of Pines needs different conditions, according to the climate of the area they are grown in.
Light. Full sun. Lack of light will make the needles extend. Plenty of sun will keep the needles shorter.
Over wintering. Tolerant of low temperatures down to 20 – 30 Celsius or lower, depending on the specimens. If not snow covered, keep the trees from frosty winds, which will dry them out.
Watering. Don’t let the Pine be too wet. It is important to let Pines get lightly dry between watering.
In the period when new needles develop it is important to keep the Pine to the dry side, in order to develop shorter needles. Keep the needles from being too wet in this period.
Especially the Japanese Black Pine is very sensitive to wet soil, and easily gets root rod. In general it is extremely important to keep a very well draining soil for Pines that allows the water to sieve right trough the soil when watering. A well draining soil will add gases to the roots, that is especially important for Pines.
Fertilizers. In springtime fertilizing starts using a mild solution of 0-10-10 NPK. Until buds begin to develop the strength of fertilizer is increased with a normal fertilizer. I always use organic fertilizing pellets like Biogold for this purpose.
When buds begin to swell, the fertilizing should be stopped immediately, and being withheld until the new needles are fully developed and hardened. This is when the needles are dark green and feels hard. The non fertilizing period will keep the needles shorter. If you need extended growth on a week tree, skip this faze.
After the needle development period, it is time to add fertilizers again. In midd-autumn until end of autumn, a 0-10-10 NPK fertilizer is used. This will trengthen roots for the winter.
Soil. The soil used for Pines has to be very well draining. Constantly wet soil will kill a Pine.
Use a very coarse soil with grit, and Pine-bark added. Pine-bark will help the formation of the helpful fungi called Mykhorriza. The fungi help the Pine getting nutrients and water, and the Pine gives back hormones to the benefit of the fungi.
My successful soil mixture that is good for the climate in Northern Europe is:
25% Sphagnum, 25% Pine-bark, and 50% grit.
In warmer climates Akadama are very useful. Akadama is Japanese hard burned clay that can be used where the air humidity is relatively high.
Every experienced bonsai grower will over time develop their own recipes for a successful soil, that should be adapted to climate of the area the trees are living in.
Repotting. As a basic guideline Pines prefer a deep pot. There should be tree too four years between the repotting of Pines. Young vigorous specimens might be replanted every second year until growth slows down.
The roots of a tree develops slowly the first year after repotting, and root pruning. The second year the roots grows faster, and the third year the root growth is at is strongest. After this year it is advisable to repot and root prune in order to develop new fine roots.
The time schedule of replanting is also taking into account that the soil mixture will be broken down in a time scale of tree or four years, and needs to be renewed.
Always pay attention to the well being of the tree. If it is week or seems to be too slow growing without visible signs on the tree, it nearly always has to do with the health of the roots. Simply replant the tree immediately, and in the case of root rot it is strongly recommended to plant the tree in pure grit.
It is important only to use dry soil when replanting, in order not to press the soil too tightly when replanting. After replanting is ended, the soil should be watered thoroughly.
Pruning. The time to prune depends of which kind of Pine that should be pruned. In general it is time to prune when your tree is in slow growth during autumn and winter. This will prevent sap loss, which is stressing the tree.
When pruning it is wise to leave a small stump that will dry out during the next months. This is done to give the tree time to find new ways to lead the sap from the cutting area, and will leave back a natural Jin/ dead branch.
Always use a sealer to cover the wound after pruning, in order too reduce sap flow.
Pinching. There are two kinds of pinching. New candles are pinched back when they develops during spring or early summer, and old needles are pruned or pinched during summer or autumn. This is one of the more demanding and difficult techniques of growing Pines as bonsais, and a section on this website is dedicated too explain the rules of pinching. A different specimen needs different treatment.
Wiring.The ideal time to wire Pines is during winter. At this time the branches don’t thicken and the n ew buds are hardened, and are not damaged as easily as during autumn. In autumn the Pine develops new buds that are very fragile, and breaks of by just a small tough.
An alternative time of year to wire is in midd summer, after the new needles are developed. Take care though, that branches is thickening faster, and especially in autumn when root growth are extended. A branch that is expanding will get scars from the wire, and on Pines they might never disappear again.