How often should I fertilize my bonsai and what should I use?
> Probably the most important rule about fertilizing is to never feed a tree that is under stress. The causes of stress are many, ranging from over watering or under watering to newly pruned roots or disease.
> Once again, it is so very important to know what type of tree your bonsai is.
Different types have specific needs as to the type and frequency of fertilization.
> Many enthusiasts who have some experience think the safest method, with no fuss, is 4 month type of 14-14-14 time release fertilizer, such as Osmocote. This is incorporated right into the potting mix or sprinkled on the surface and worked down into the mix.
> Most broadleaf trees and tropicals can be fed with any general houseplant or garden fertilizer.
> Conifers, azaleas and certain others can benefit from a monthly application of an acidic fertilizer, such as MirAcid.
> Some growers include hormones such as Superthrive in their regimen to stimulate root production.
> Trees should only be fertilized when in periods of active growth. This is generally from midspring through early summer and from late summer to early fall.
> If your summers are extremely hot and your trees are outdoors, do not fertilize until temperatures have moderated and growth has resumed.
> Likewise, do not feed trees in winter when they are either dormant or growth has slowed down.
> Some growers prefer organic fertilizers over chemicals. This is an ongoing debate and much too lengthy to go into detail here.