Valavanis Bonsai Hints
Part 1– Spring Transplanting
William N. Valavanis
Without a doubt, spring is the busiest time of the year for those training bonsai. In addition to creating and shaping new trees, most bonsai are transplanted in spring, although the exact dates may vary by months considering our vast country with 13 different U.S.D.A. climate zones. People in southern California and Florida will often have finished transplanting their trees while bonsai in the northern areas are still frozen, dormant and under snow cover for protection.
Most temperate species trained for bonsai are best transplanted in early spring. However, tropical species are often transplanted during the hot summer months when the plants are actively growing. Frequency of transplanting and root pruning depends on many factors such as: species, developmental stage and purpose. Generally deciduous species require more frequently transplanting than broad leaf and narrow leaf evergreens. Developed bonsai require less frequent transplanting than those that have not developed the desired shape.
Species are commonly transplanted in early spring prior to bud break when the trees are awakening from dormancy just as the vegetative buds begin to swell. The roots are often just beginning to grow and will quickly recover from root pruning. Deciduous species awaken from dormancy earlier than broad leaf and narrow leaf evergreens so they are transplanted and root pruned first. Broad leaf and narrow leaf evergreens awaken from dormancy later than deciduous species and are transplanted later in spring. Although there are ideal times when to root prune and transplant, professionals with knowledge, skill and a bit of luck, can successfully transplant any species any time of the year with controlled aftercare.
After potting its best to put green moss on the soil surface to maintain a bit of moisture in the media, provide some erosion control on high areas and to present a better image. If green moss is not available cut up long-fiber sphagnum moss is an excellent substitute. I transplant so many deciduous bonsai in spring it’s difficult to find the time to plant green moss on all my trees so I usually use cut up long-fiber sphagnum moss. The best comes from New Zealand and Chile which orchid growers use in the media and is quite clean. Usually the long-fiber sphagnum moss obtained at garden centers contains sticks and is dusty. Look for “orchid moss” at garden centers and greenhouses. Lowe’s Home Improvement Centers often carry orchid moss in small bags that are the size of a loaf of bread quite inexpensively. Most importantly, covering the soil surface prevents soil from splashing the trunk and getting the bark dirty. It is best to apply any either kind of moss on the soil surface when the soil is dry, not after watering the bonsai. Planting and pressing green moss or long-fiber sphagnum moss into wet soil applies pressure and often compacts the soil and removes important areas for proper air circulation.
A thorough watering is necessary immediately after transplanting because the soil mix is dry so it works in between fine roots and draws moisture from the roots. Usually soaking the bonsai from the bottom, while gently overhead watering from the top at the same time is best because water will quickly be distributed throughout the soil mix. When watering from the top the water peculating through the soil mix will push out any fine dust that remains in the soil. Watering from the bottom only, as with soaking, will not filter out the fine particles. If only watering from the top, its best to keep applying water until it runs clear through the drainage holes thus removing the fine dusty soil particles. Although controversial, for the past 40 plus years I have always used an additive to reduce transplanting shock such as SuperThrive and HB 101 at the first watering after transplanting, either when watering from the top or soaking from the bottom. Actually, I use both weekly mixed in with my liquid fertilizer.
It is important to keep newly transplanted trees above freezing temperatures to avoid plant tissue injury that will slow down recovery from root pruning. In cold climates I have discovered it is best to wait until small new leaves begin to open or are even open a little on deciduous species before transplanting and root pruning. If transplanted before bud break and low temperatures occur the recovery time will be delayed and the plants will just sit without growing. I tend to transplant deciduous species later in spring when the plants are growing, usually in warmer temperatures because the plants will simply continue to grow without setback.
After transplanting it is best to keep broad leaf and evergreen species out of the strong sun and wind for a few weeks. They should not be fertilized until after they have recovered from root pruning. Since deciduous species do not have foliage I usually put them directly outside in full sun, but carefully watched for drying out. However, all species should be carefully watched and protected from severe weather. If deciduous species are kept protected for a long time in a shady location normal growth and foliage color may not develop correctly.