Japanese maple, a woody plant native to Japan, North and South Korea, Mongolia and Eastern Russia, comes in a number of variations. These different forms, called cultivars, each have certain special characteristics that identify them from the rest. The acer atropurpureum is one such variation. It, just like its parent species, is a perfect specimen for bonsai art.
The acer atropurpureum is a small tree naturally reaching a mere 4 meters in height. What starts as a green bark when the tree is young ends up grey or brown as it reaches maturity. It has lobbed leaves just like other forms of Japanese maple. However, what sets the atropurpureum from the rest is its distinct deep lobes. Autumn turns the red leaves into a pronounced crimson and during spring, striking purple flowers emerge. These stunning visual qualities are what make the tree a darling to bonsai enthusiasts.
It takes at least three years before you can start training the tree. Once it has taken its full bonsai shape, the tree has a low growing crown which gives the tree rather majestic proportions. When in full leaf, the tree appears heavily covered as opposed to some species where the branches are overly exposed. It has a stout gray trunk which hardens and develops deep furrows as the tree ages.
Acer atropurpureum bonsai trees are hardy and highly adaptable trees. Although it may look small and cute to watch, this maple bonsai is not a house plant. It is the same wild tree in a miniature form. As such, it is best located outside but also fares well indoors so long it receives 5-6 hours of sunlight per day.
The positioning of any bonsai may not instantly kill it, of course, but it may destroy the tree with time or at least affect its appearance. Exposure to sunlight is one of the most important factors when deciding where to put your Japanese red maple bonsai tree. It is a must for the tree to receive ample sunlight in the morning.
During hot summer afternoons, the tree must be shielded from direct sunlight. The intense heat causes dissolved minerals to build up in the leaves which turn them brown. The acer atropurpureum’s delicate foliage is susceptible to drying out around the edges when exposed to too much sun. The drying is more pronounced at the edges.
The effect of direct sunlight is not only limited to the leaves. Even the roots may be baked and the results are seen in a withered crown.
Harsh winds can be devastating to your Japanese red maple bonsai tree. The foliage of unprotected trees may suffer leaf damage and, if the tree’s root system is not fully formed and firm enough, it may outright be uprooted.
Naturally, trees have their roots buried deep in the ground, which protects them freezing. For bonsai, the burying isn’t that thick and this poses a huge threat to the root system. Temperatures down to -10 degrees Celsius are bearable, but anything below that can be harmful.
Although acer atropurpureum trees make highly adaptable bonsai, care should be taken when it comes to watering. Wrong watering methods will kill your tree more than any other problem. Atropurureum bonsai thrive in moist to wet soil. An extra eye should be paid to make sure the plant’s pot is never completely dry. Usually, watering the tree once a day will see to this. But, during the hottest summer days, a frequency of twice a day will keep your bonsai healthy. However, even in hot times, the importance of ample drainage still stands. The soil should never be water-logged as it leads to root rot and problems absorbing nutrients.
In hot seasons, water the tree before the sun rises and temperatures soar. This gives it ample time to soak its systems up before the rapid loss of water that comes with the afternoon’s heat.
Just like most Japanese maples, acer atropurpureum prefer water with neutral to slightly acidic levels. In this case, limey water should be avoided.
In the wild, the acer atropurpureum has its roots deep in the earth that’s constantly being replenished with nutrients from dead plants and animals and biological waste. For your bonsai, the soil in the small pot cannot just hold nutrients enough to last more than a few weeks. You have to manually add the fertilizer.
There are several things to consider when it comes to feeding your bonsai. Age of the tree, season, size of the pot, and the concentration of the fertilizer. You don’t need any special fertilizers. An all-purpose liquid fertilizer obtainable from any decent gardening shop will suffice.
The tree should be fed once a fortnight so long you halve its strength. A too strong fertilizer will burn the roots and brown the leaves. If you opt for a slow-acting organic fertilizer, take breaks of 20 to 30 days between feeding.
Avoid feeding a tree that’s been weakened by disease or weather elements. After re-potting as well, the tree should be allowed to fully establish itself in the new pot for two months before you can feed it.
During times of the raging summer sun, a two-month long feeding break should be observed. The action of the heat on the fertilizer has a negative impact on your bonsai.
Winter is a period of dormancy when the tree’s growth ceases. There is no need to feed the tree during this time.
To shape your bonsai, it is necessary to prune certain parts of the crown. Although you can prune new shoots and small twigs throughout the year, trimming of mature branches should be done in autumn or summer when the tree is most capable of callus sealing. Spring pruning leads to excessive sap bleeding. To avoid fungal attacks, which tend to enter the tree through the prune wounds, it is advisable to apply cut paste.
The root system also needs pruning when repotting the plants. This is also the right time to prune your bonsai’s branches to match the reduced nutrient and water supply from the roots.
Although the acer atropurpureum is mainly shaped by pruning and leaf pinching, it may be necessary to wire the tree. This should be done in summer with the bonsai in full-leaf. To prevent the wire from cutting into the flesh of the tree, wrap them before wiring. Each wiring period should not last more than six months. For trunk shaping, an appropriately positioned stake can be used to bind the tree to your desired shape.
Japanese red maple bonsai are best repotted in spring. This should be done once a year for young trees, and once every three years for the older plants. With every re-pot, the roots should be sufficiently pruned. The root system is rapidly recovered and fills the pot in little time. Pruning the roots should be accompanied by branch pruning to balance the intake of water and nutrients with the consumption above.
The root system will most likely have a couple of dead roots. These have to be removed to prevent root rot. Young trees can have all the soil removed and their roots washed for easy placement. But older trees need to be transplanted with a ball of soil still on.
Aphids: These pests attack acer atropurureum in spring. Ordinary gardening insecticide handles the problem.
Verticillium Wilt: This attacks the tree through wounds and cuts. It appears as a black spot on open skin of the bonsai tree. The disease results in partial death of the tree and in extreme cases, the whole tree is damaged. The worst part about verticillium wilt is that it is difficult to treat and can spread from tree to tree through your bonsai tools.
Root Rot: Root can be problematic. But, its cause is well known and prevention is simple. Water-logged pots are the culprit. Your pot should have sufficient holes in it and you should time your watering intervals to maintain moist but not overly wet soils.
Root rot can also come through dead roots which then spread the problem to the healthy ones. All dead roots should be removed upon repotting.
Acer atropurpureum can be propagated by grafting or from seeds. Propagation by seeds is easy and can be done from home.
Defoliation gives the tree better branches and nicely spaced internodes. You should prune your bonsai’s leaves every two years. The defoliation is best performed in early summer when the tree is going through a season of rapid growth.
Lighter leaf pruning can be done every year. The target should be large leaves and those that are densely spaced. The result is pleasantly small leaves and more bud-sprouts which lead to a dense crown typical of great bonsai.
A well-grown Japanese maple bonsai has closely spaced internodes. To achieve this, pinch back new growth leaving only two pairs of leaves. One rule to observe is not to defoliate the same year that the bonsai is repotted.