The best way to water a bonsai is to stand it in water, to just below the rim of the pot, for at least 10minutes. This will ensure that the soil is fully saturated. Check the surface of the soil with fingertip daily, & when dry to the touch, stand in water again. Watering needs vary according to size of tree/pot, rate of growth, time of year & situation, however following this regime you will get to know the requirements of your trees. They need to be well watered, then allowed to drain, NOT kept fully saturated all the time - roots need air too to function well. In hard water areas use rainwater - a build up of lime in the soil is harmful.
Raising the humidity level is very important when keeping trees indoors, & mist spraying is an excellent method. WARNING - Beginners Beware - This will NOT water the tree but will moisten the surface of the soil. Check the surface with a fingertip BEFORE spraying, so you know when your tree needs watering properly again. Outdoors the British climate rarely necessitates additional moisture, however during dry spells mist spray as described. In all cases late afternoon or evening is the best time to spray, as strong sun on wet foliage causes damage both through glass & outdoors.
Healthy trees thrive when given the additional salts, minerals & trace elements they need. However if your tree appears unwell stop feeding until the problem is resolved & it is growing vigorously again. We recommend the use of slow release organic fertilisers - dry granules that are rubbed into the surface of the soil & are slowly absorbed as required when the tree is watered. Assuming that the compost is good, one pinch per month should be ample, during the growing season. If you have an indoor tree that continues to grow well during the winter, you may continue to feed less frequently, but stop feeding when dormant or, as mentioned above, when poorly. There are numerous liquid feeds on the market & powders that are added to water. If you use these types of fertiliser do ensure that your tree is well watered before adding - liquid feed can burn roots if the soil is dry.
In general we use the compost that we make here for most types of tree [adding more grit for pines etc]. We have described its composition in our booklet entitled "Introduction & General Care of Bonsai", which we wrote for first-time bonsai growers & give away free with every tree. Copies available on request for £1.00 + an A5 s.a.e. Good bonsai compost should contain plenty of horticultural grit to aid the development of feeder roots & ensure a good free-draining mix. Years ago we bought a ready-made bag of "bonsai compost" [so called] but were disappointed to find that it did not contain the necessary amount of grit, leaf mold etc. This prompted us to put our compost into bags for our customers. All gardeners say their own compost is the best & we are no exception!
Repot & Root-prune
We repot to provide fresh, fertile compost, to ensure that we maintain a healthy root system that has room to develop, and, or, to change the appearance / planting style. Trees grow fastest when young, the rate of growth slowing with maturity, so in general we repot the younger trees every 2 - 3 years and older trees as & when necessary. The best time to repot is early spring or late autumn when the tree is dormant, not in the spring / summer when it is growing fast and the roots need to be functioning at optimum. Now is the time to check the root system, and if there are roots winding round the pot tease them out gently and trim back. In this way you provide space for new roots to develop, promote more vigorous growth, and prevent the roots from choking themselves. Treat with care after repotting / root-pruning to minimise stress, particularly with indoor trees & other evergreens as they are still maintaining the top foliage albeit slowly. A little more shade, if usually situated in a very bright spot, will aid recovery.
All trees need plenty of light, and good air circulation. Outdoors protect from direct sun and wind. Indoors do not place too close to the window [especially when south- facing], where foliage can be burned through glass, or close to a source of heat, such as a radiator or television.
Most frequently problems arise when trees are not watered correctly, and, or, are badly situated. Following the notes above will rectify these difficulties simply and quickly. Pests such as greenfly can be eradicated by spraying with a proprietary insecticide available at most garden centres. However trees can withstand pests like these in large numbers, so if you are experiencing serious problems the humble greenfly may not be the culprit. A poorly tree is more susceptible to damage by pests or fungal attack. Whilst I do not rule out the use of a pesticide or fungicide when absolutely necessary, I do recommend a thorough examination of the circumstances that may have led to a weakening of the tree prior to the infestation.
Please let us know if there are other topics that you would like included here.