These can usually be sown at any time of year. It is often helpful to pre-chill the seeds. Whether pre-chilling or not, most large seeds benefit from being soaked for 1-2 hours in luke warm water before sowing. For most types a free draining seed compost is preferable. The seeds can be sown individually or several to a Sin (7.5cm) pot which should be carefully labelled with a plastic label and waterproof pen or pencil. It is also helpful to enclose the seed container inside a polythene bag until germination as this prevents the compost from drying out. Provide the specified temperature by placing in a propagator, cold frame or on a well lit but not sunny windowsill and once the seedlings start to emerge remove the bag and lower the temperature to around 60°F (15°C). Give the seedlings plenty of light but shade from the strongest rays of the sun.An alternative method which is relatively foolproof but usually slower is to plunge the pots, after sowing, up to their rims in a shady part of the garden or a cold frame. In the former case it helps to cover each pot with a large upturned jam jar or piece of glass. The compost must always be moist but never soggy and germination can take over 12 months in some cases. This method is the natural way of breaking dormancy as over the winter the seeds experience the slow freezing and thawing which is often necessary before seeds will germinate. Whichever way they have been started off, when the seedlings are large enough to handle transplant them carefully into Sin (7.5cm) pots of a similar potting compost and grow cool and well lit. Once they show signs of becoming established, plunge the pots in a cold frame or sink them level with the soil outdoors in a shady sheltered part of the garden. Keep the pots well watered during the late spring and summer and plant out 12-24in (30-60cm) apart in autumn into a reserve border made up of well drained garden soil, mixed with well rotted compost or peat. Usually after 2-3 years you can plant them out into their final positions.
Treat these as described for Tree & Shrub seeds above but once the seedlings are well rooted into their pots they can be placed in their Bonsai containers, spring being the best time. The compost used should be gritty and free draining to ensure that it never becomes waterlogged. Water the pot 2-3 hours before transplanting and make sure that the Bonsai pot has its drainage holes covered with 'crocks' or brick rubble etc. and that the compost is moist but not over wet. Pot firmly, working compost into all the crevices among the roots and then water thoroughly. Stand the plant in a shady, sheltered place for about 1-2 weeks to enable it to become established and then move to the permanent position. After this keep the plant uniformly moist and in good light. Syringe the foliage regularly on hot days. Once the subject is well rooted into its new container careful pruning can be done taking care to stop the leader when the specimen reaches the desired height, but also allowing for natural shape.
Root pruning at this stage will be unnecessary but always remember to repot at least yearly to retain a healthy Bonsai. Root pruning is necessary when the tap root becomes too large for the pot. Thin this down so that the roots fit easily into your pot making sure you have left sufficient feeding roots (normally fine roots horizontal to the tap root) for the tree to thrive. Always pay particular attention to watering after this exercise.
Bonsai should for the most part be grown outside. Shelves and benches will show them off but they can be kept on balconies or roofs. Their requirements are simple, water and sunshine. They should, however, have some protection from the brightest sunlight and from hard frost during the winter.
Remember they are HARDY plants and should not be kept indoors for more than a few days at a time.