In general, every two weeks feed bonsai with a high-nitrogen fertilizer from late spring, and then in summer feed them with a balanced fertilizer, stopping for four weeks during the hottest part of the summer and starting again in late summer with a low-nitrogen or tomato fertilizer. High-nitrogen fertilizer feeds leaves and buds, and low-nitrogen fertilizer feeds twigs, roots, trunks and branches.
Spray bonsai with foliar feed every two weeks in spring, and mist the foliage with water in the warm summer to keep the humidity levels up. To avoid lush or soft growth initially, such as in pines or maples, use a zero-based nitrogen fertilizer, 0-10-10 or at the worst a low-nitrogen fertilizer such as tomato fertilizer at the beginning of the season. to get bright autumn colours in maples, do not feed them more than twice in the entire season.
It is important to remember that using liquid feeds allows the food to pass quickly through the soil, and if the soil is correct, then some will be retained during the feeding process. While watering during rain is sometimes unavoidable, soil and foliar-feeding of bonsai with large canopies of foliage during rain is not a good idea, as the water will wash through the soil much faster.
Small trees can be immersed in a bucket or sink filled with feed, and when the bubbles stop rising the tree will have received sufficient food and water. Do not do this every day if you have outdoor trees. On the other hand it may be the only available method for an indoor tree. (if you live in a flat or apartment) In that case, you will probably find that your tree will only need watering once or twice a week and feeding once every two weeks.
[hr]| Period | Very Young Trees | Trees in Training | Established Trees |
| Winter Dormancy | No Feed | No Feed | No Feed |
| Early Spring (At bud break wait until the leaf has fully opened) | Start feeding high-nitrogen fertilizer at half strength. Feed every week. | To avoid lush growth, feed a zero nitrogen fertilizer, such as 0-10-10, or tomato feed. Feed two weeks at half strength. | Zero-nitrogen feed once in early spring. |
| Late Spring (Leaves are now fully developed and candles are swelling on pines. Protect from winds, as the leaves are soft) | Feed at half strength every week. Increase to full strength at the end of this period. | Continue to feed every two weeks, but now start introducing high-nitrogen fertilizer. | Feed once with high-nitrogen fertilizer at half strength. |
| Early Summer (Leaves are now firming up, so continue with feeding. Protect from pests) | Increase to full strength high-nitrogen feed. Use a balanced fertilizer towards the end of this period. | Use a balanced fertilizer at help-strength every three weeks. Or start to use slow-release cake fertilizer: Maples, elms and zelkovas need less feed, to develop fine twigs. | One feed of high-nitrogen fertilizer and plant tonic during this period. Do not overfeed established trees, as they will grow to length. |
| Mid-Summer (The tree enters a semi-dormant period at this stage, so it is wiser to stop feeding for between two to four weeks) | Stop feed. | Stop feed. | Stop feed. |
| Late Summer (This is the period prior to leaf change, but after the heat of mid-summer) | Start using a low-nitrogen fertilizer every week at full strength. Use a foliar feed as well each week. | Start using a low-nitrogen fertilizer every week at full strength. Use a foliar feed as well each week. | Two applications of low-nitrogen fertilizer or, even better, 0-10-10, during this period. Foliar feed once. |
| Autumn (Leaf change heralds the onset of dormancy in deciduous trees) | Stop feeding when leaves start to change. Keep feeding evergreens. | Reduce feed when leaves start to change. Keep feeding evergreens. | Stop feeding deciduous trees, but give evergreens one more application in late autumn. |
Always Remember:
- Do not feed deciduous trees before bud break
- Do not feed in winter, because trees cannot absorb the feed
- Do not feed sick trees, as they will not be able to absorb nutrients easily
- Do not feed after repotting for at least 6 to 8 weeks, as the delicate roots can be damaged
