Growing Bonsai from Seed

Growing bonsai from seed remains the simplest and most natural method of propagation but by no means the most reliable. It also requires a great deal of patience, particularly with very slow-growing trees. It can take anything up to five years to obtain a bonsai from seed.

How to obtain seeds

You should look for wild seeds in autumn. With a little skill, you will find a variety of seeds lying about. But you may encounter the dual problem of finding which tree the seed has come from and what kind it is. This is no problem with acorns or chestnuts, but the problem becomes acute where several species of conifer grow in the same place.

It should also be emphasized that the chances of successfully germinating seeds found in nature are very poor. Some seeds may have been attacked by parasites which threaten germination or the plant's successful development, while others may well have been contaminated by viral or fungal disease.

You should just be aware of the risks and limitations. One reliable solution is to buy selected commercial seeds. These offer a high success rate for germination and the fact that they are sold commercially means there is less risk of diseases and parasites. Seeds sold commercially expressly for producing bonsai come mainly from the Far East and are of species particularly well-suited to this method of growing. But no seeds, having germinated, grow into bonsai trees without special care. The miniaturizing technique entails no genetic modification of the trees. So bonsai seeds will produce normal sized progeny if not specially treated to produce bonsai, just as seeds intended to produce normal trees can also form bonsai. A word about the magnificent trees often pictured on seed packets. These are superb examples of what can be achieved but not the kind of result you can rely upon if you buy the packet.

Preparing the seeds

Whereas many of the smaller seeds can be sown directly in autumn or spring, this is not the case for the larger seeds, particularly if they have a hard coating like a shell. This is true of most tree seeds. They should be left to soak in tepid water for at least 24 hours. If the protective coating is hard or thick, it may be necessary to make an incision, without damaging the seed inside. If the seed is protected by an outer shell, this should be carefully broken open with pliers, taking care not to crush the seed.

Often the seed will not germinate without special treatment, known as stratification. This technique consists of forming alternate layers of seeds and moist sand. This softens the seeds and helps them to germinate, which considerably increases the chances of success. Be prepared to wait, as this form of seed preparation may take several months or a year, depending on the species.

Before sowing, it is worth soaking the seeds in disinfectant to limit the risk of fungal diseases when the seedlings start to sprout (e.g. damping off disease of seedlings). However, as damping off is one of the most likely causes of failure with bonsai seedlings, you should be prepared to spray or dust with a fungicide within a few days of the seeds germinating.

Where to sow

Soil

For most bonsai, the ideal compost for seed-sowing consists of equal parts of peat, loam and sand. This standard composition can be adjusted to suit the special demands of particular species. Although this mixture suits most plants, it cannot be used for heath land shrubs, which need a very acid soil.
The best for bonsai seedlings is pure peat, or peat with sand. Take particular care to ensure that the potting compost is kept moist. So as not to impede the development of young roots, the potting compost should be cleared of the larger impurities and any pebbles which it may contain. It may even be useful to pass it through a coarse garden sieve. Any soil used to cover the bonsai seeds should be passed through a fine mesh garden sieve. To prevent disease, the soil should be disinfected with a product based on formalin or with steam. This could produce good results with earth taken from nature, which should be carefully passed through a sieve. Any unwanted seeds and fragments of root should be removed to prevent them growing at the same time as the bonsai seeds sown. Such weeds' are difficult to remove later without damaging the bonsai seedling.

Containers

Once the bonsai seedling has sprouted its first pair of leaves, it should be potted on several times. Great care should be taken not to damage the bonsai seedling or its roots. The bonsai roots are especially delicate and should not be pruned at this stage. Therefore the container used for sowing can be considered temporary and not as important as the tray in which the bonsai will later be planted.
Though some may favor sowing bonsai seeds in trays or bowls, it is good to use small pots, especially for big seeds. A peat pot has the advantage of avoiding the shock of transplanting, since the pot itself disintegrates. But watch that the peat does not dry out. By contrast, clay pots hold the moisture in the compost very well indeed.

Sowing technique

Whatever container is used for your bonsai, it is essential to cover the base with a layer of fine gravel or sand to ensure good drainage after watering. The bonsai container should have a drainage hole, so excess water can drain away.

Fill the pot with suitable potting compost to within about 2 cm (3/4 in) of the rim. Lightly pat down the soil with a small wooden presser. Sow the bonsai seeds thinly so they are not overcrowded when they germinate. Large seeds can be sown individually, smaller seeds sown with a seeder. If you do not have a seeder, use a piece of stiff cardboard folded in two from which the seeds are gently tapped.

Now cover the seeds with a layer of compost passed through a fine sieve. The depth of compost covering the seeds will vary with the size of the seeds. The largest will need 1-2 cm (3/8 - 3/4 in) layer of compost, whereas smaller seeds require only a mere dusting. The tiniest seeds are best not covered, as this can stop them sprouting.

The surface of the compost should be lightly firmed with a wooden tamp or presser; do not firm it too much, as the seeds should still be able to 'breathe'. Immediately afterwards, give them their first careful watering. Give them a fine spray, so the surface layer of soil is not disturbed. Again, the size of the seeds and thickness of the surface layer will influence the method of watering. Large, well covered seeds can be watered with a can fitted with a fine rose, but small seeds covered with a thin layer of compost should be watered with a fine mist from a hand sprayer. Tiny seeds not covered with compost should be watered from below by standing the container in a tray containing water until the compost is saturated. Be careful that the water which rises by capillary action does not disperse the seeds when it reaches the surface.

A propagator is an ideal container: keep the pots in it in a shady place at a temperature of 15-20°C (60-70°F). Trays and bowls should be covered with a sheet of glass, leaving one corner open to let the air circulate, to limit evaporation and to keep the soil surface at the right temperature. If you do not have a sheet of glass, stand the containers in a frame or, if the temperature is likely to remain above 10°C (50° F) and there is no night frost, simply stand on a balcony. There is normally a risk of frost in temperate zones from late autumn, and so seeds should then be taken in and stood in a cool place near a sunny window. Make sure that watering is frequent enough if the room temperature is warm and the atmosphere dry. It may be necessary to stand the bonsai container in water regularly once the seeds have sprouted.

Once you have sown your seeds, you will need a great deal of patience, since most bonsai seeds take several months to germinate. Some may not even sprout until the following year.

Initial care

Germination is followed by the rapid development of the young bonsai which quickly develops roots, loses its seed-leaves and produces true leaves. But the bonsai seedling remains fragile and so a watchful eye should be kept on it. Make sure the moisture level is adequate to keep bonsai growing but not excessive, so it encourages fungal disease, such as damping off. To avoid severe dehydration, the bonsai seedling should not be exposed to direct sunlight. It should be gradually hardened to both cold and heat. If the season is suitable, the seedling can be potted on after a few months. At this stage, an ordinary clay pot should be used, as the plant cannot yet be thought of as a bonsai. One can now start to feed the plant with fertilizer to promote its development. The bonsai pot should be stood outdoors, weather permitting.

If you have a garden, you might be able to plant your bonsai in a bed for its first year, although you will have to monitor development carefully, to ensure that the seedling does not grow too quickly to be suitable for bonsai training later. These roots sometimes reach astonishing proportions, to stunning effect. Such bonsai can make a spectacular contribution to the decor of a room.

Bonsai treatment should start in the second year after germination, though its first potting in a bonsai tray will not take place until the end of its third year. Throughout this time, whether you use pots or plant out in beds, make sure that no weeds develop to the detriment of the seedling.