Bonsai care (oriental hornbeam)

Placement

The oriental hornbeam is not a houseplant, so it should spend most of the year outdoors. It loves light. Keep it in a bright spot, but in summer shield it from the scorching midday sun.
From June through August you can keep it indoors, in a well-lit place. From September, though, be sure to move it back outside.

Watering

A bonsai needs regular, careful watering.
In nature, a tree’s roots grow deep into the ground. If it doesn’t rain for a while, the tree can still get the water and nutrients it needs through those deep roots.

Confined to a pot, a bonsai has no way to steer its roots in the direction it needs. There is very little soil in a pot, so a bonsai depends far more on watering than a tree growing in nature does.

It is also worth noting that on hot summer days, the movement of water through the tree and its evaporation from the leaves regulate the plant’s temperature and protect it from overheating. As long as the soil is moist, a tree can keep developing normally even in very high temperatures. When water runs short, however, “scorch” spots appear on the leaves and shoots, which ultimately causes the tree to dry out and die.

How much and how often to water

How often a bonsai needs watering depends on the conditions it’s kept in, the soil in the pot and the species itself. A bonsai should be watered not on a strict schedule, but as it needs it. In late spring and summer, for example, watering once a day may not be enough. There is another common misconception: that watering while direct sunlight is falling on the tree is harmful. In summer it is sometimes even essential to water a bonsai during the sunny part of the day. So don’t set yourself a fixed routine along the lines of: “The bonsai must be watered once a day, in the evening.”

Some species need soil that is constantly moist, others need less moisture, but letting the soil dry out completely for a day or two very often kills the tree. Be sure to check the condition of the soil every day and water whenever it is needed.

There are a few simple signs that the soil is drying out: as the soil begins to dry, its surface changes color; dry soil is also noticeably harder on the surface. If your bonsai has been in its pot for a few months, you can also tell whether it needs water by picking it up. The difference in weight is quite noticeable — dry soil is considerably lighter. On deciduous trees, the first sign of late watering is drooping leaves and fresh shoots. Bonsai are watered with a special small watering can that lets the water flow out gently. Pouring a large amount of water all at once washes away the soil surface and leaves hollows here and there.

Use ordinary tap water for watering. Its downside is the chlorine and high mineral salt content. After regular watering with such water, the surface roots and the rim of the pot become covered with a white deposit. You will need to remove this deposit from time to time.

Make sure that after watering, water comes out of the drainage holes; otherwise only the surface may get wet while the soil deeper down stays dry. It often happens that a bonsai is planted in its pot in such a way that much of the water poured on runs off the surface and over the edge of the pot. In that case, pour the water slowly, only as much as the surface can hold without overflowing, wait for it to soak in, then add more, until you are sure the soil in the pot is thoroughly wet. The sign of thoroughly wetted soil is water running out of the drainage hole.

Suppose the soil in the pot has dried out completely. If you look closely at the pot in such a case, you’ll see a gap has formed between the pot and the soil. If we water it in this state, most of the water will run straight through the gap and out of the drainage hole.

In this case it is better to set the tree in a vessel larger than its pot, fill it with water up to the rim of the pot, and lift it out once the soil surface is wet. The excess water will drain out through the drainage holes. In spring and summer a tree needs much more water than in late autumn or winter. In winter it may turn out that you water the tree only once a month for the whole season (do not water a bonsai during frosts).

The time of day you water a bonsai also matters. In late spring and summer, when temperatures are high, try to water so that the soil in the pot stays moist through the night. Water in the evening, after sunset. If you water only in the morning or at midday, the soil will soon dry out and the tree will spend practically the whole night in dry soil. In autumn, when the sun is no longer so fierce, you can water your bonsai at any time of day, though morning is best.

As for overwatering: when the soil around the roots is constantly wet, the amount of oxygen in the soil drops. This then causes the fine roots to deteriorate. The damaged roots begin to rot, and if the process is not stopped, a large part of the root system gradually rots away. As a result, the tree first weakens and, if the situation is not corrected, dies. So once you have watered a bonsai thoroughly, let the soil dry out gradually, and only then water again.

Soil in a pot can also become waterlogged from prolonged rain. But even a week of non-stop rain will not harm the tree. The danger is when the soil in the pot stays saturated with water constantly, throughout the whole season.

Bonsai care in winter

In winter, trees are dormant, and their active growth is suspended until spring. The dormant period is just as essential to a tree’s vitality as the period of active growth. That is why bringing a bonsai into the warmth in winter simply because it “might get cold” is fatal for the tree. Of course, bringing it indoors for a day or two to decorate the room will do no harm. But if it spends the whole winter in the warmth, it will certainly die.

In temperate regions where winters are not too harsh, a bonsai needs no special conditions for overwintering. But in regions where winter temperatures regularly drop low (-5°C and below), the tree must be protected from frost. This applies above all to the roots. A bonsai’s roots are not buried deep in the ground, so they can freeze easily. In Tbilisi’s climate the risk of freezing is lower. But if severe frosts last for a long time, take a container much larger than the pot and bury the tree, pot and all, in sand or sawdust. Under these conditions the roots are relatively well protected from the frost.

Protecting bonsai in summer

At temperatures above 30°C, unless we take special measures to protect a bonsai, the tree may be damaged or even die. How well a tree copes with abnormally high heat depends on its own heat tolerance and on how many hours a day the high temperature lasts.

The effect of heat is easy to see on a deciduous tree. A tree cools itself through its leaves, by evaporating water. In high temperatures it loses moisture quickly. When a bonsai gets too little water in the heat, the leaf temperature can reach a critical point. Wilting leaves are the first symptom of water shortage. In extreme heat a tree may go dormant prematurely (as it does in autumn). The leaves change color and drop — first those inside and at the bottom of the canopy, then the rest. When direct sunlight falls on a bonsai, the soil in the pot also heats up considerably. High temperatures can damage the roots as well. Under such conditions the tree becomes less resistant to diseases and pests. These processes are hard to spot on conifers, however, because their needles don’t give such a “signal.” That is exactly why conifers need special attention in summer.

A tree can cope quite well with very high temperatures if you give it normal conditions to function. There are a few simple ways to protect a bonsai from extreme heat. Keep it out of direct midday sun, or rig up some kind of shade. Don’t place a bonsai on a surface that gets hot in the sun — stone, concrete, metal; try to raise the humidity around the bonsai: mist it more often and water the area around it. Make sure the soil in the pot never dries out completely. Watering at midday is another way to cool the roots.

Fertilizer

For normal growth and development, besides carbon (C), hydrogen (H) and oxygen (O), which a tree takes from air and water, a tree needs to take up macro- and micronutrients from the soil. The macronutrients are nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg). Various micronutrients are also needed in very small doses: iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), boron (B), manganese (Mn), sodium (Na) and other elements. All of these elements are vital to a plant’s existence, the macronutrients above all. An excess or shortage of any one of them has a noticeable effect on a tree’s development. For example: nitrogen is needed to regulate growth, for the leaves and for fruiting. A nitrogen deficiency soon shows up as slower growth. An excess prolongs the growth of new shoots. Nitrogen-rich fertilizer is not applied in the second half of the growing season. Phosphorus promotes the tree’s development and root growth, and increases its resistance to drought and frost. Potassium helps the tree withstand stress (very high or low temperatures, too much or too little moisture). An optimal level of potassium improves the buds’ ability to survive the winter and the tree’s resistance to fungal and bacterial diseases. Calcium is essential for normal metabolism in the plant. Because there is so little soil in a pot, the nutrients are soon used up. That is why regularly applying a fertilizer that contains all these elements is just as essential as watering. Without additional feeding a tree develops poorly, its leaves and needles lose their color, and it falls prey to disease more easily.

For bonsai you can use either organic or mineral fertilizer, but you must not mix them together and apply them that way. There is fertilizer made specifically for bonsai that contains all the necessary elements. It comes either as a liquid or as solid granules. Liquid fertilizer is dissolved in water at a set dose, and the tree is watered with the resulting solution as usual. Trees absorb liquid fertilizer quite quickly, so on conifers it is applied once every 3 weeks. Granular fertilizer acts over a longer period. It is either mixed into the soil or placed in special small baskets set on top of the soil. With every watering some of it dissolves and gradually feeds the bonsai. You can order special bonsai fertilizer online.

If you can’t find such a fertilizer, you can use a balanced compound fertilizer sold at garden centers or flower shops. As a rule, these contain all the elements plants need. For bonsai it is best to choose one that dissolves well in water, as it is more convenient to use. The packaging always lists the composition in percentages (NPK) and how much water to dissolve it in. Be very careful when fertilizing and work out the right dose precisely, because too much can kill the tree. Ideally it should be NPK 10-10-10 and contain micronutrients.

Feeding usually begins in early spring and ends in autumn. There is no need to fertilize in winter. Never fertilize a freshly repotted tree. Fertilizing is only permissible 4–5 weeks after growth begins, once the bonsai has rooted well.

At Samto Kimia you can buy “Kristalon 20-20-20” fertilizer. Dissolve 2 grams in 1.5 liters of water.

Misting

Misting is essential for both deciduous trees and conifers. Start misting once the warm weather sets in, in spring, and continue until leaf fall begins. In summer it is best to mist every day; naturally, there is no need to do so in rainy weather. Mist your bonsai when you water it.

Some water-soluble fertilizers are also intended for foliar spraying. This promotes lush, healthy leaves that are less prone to disease. There are also water-soluble foliar feeds whose spraying gives quite good results. If necessary, spray with dissolved fertilizer or foliar feed once a week, or as often as you apply fertilizer to the soil.

Diseases and pests

Like all plants, bonsai get diseases and are attacked by pests. That is why it is best to spray preventively once a month from spring to autumn. Dissolve Ridomil Gold, Strobi Star and Actellic together in water at the required doses and spray. Never spray a bonsai in an enclosed space.