What Do We Do With Bonsai In October?

In fall, bonsai are starting the slow slide into slumber. The following photo essay shares a few ideas of how to read the results of our summer work, and what to do in the bonsai garden in fall. 

This Satsuki Azalea is telling us that watering and fertilizing were adequate over the summer, as we can see flower buds setting. The flower buds are the 3 light yellow buds in the center of the shoots. Without enough summer water and fertilizer we wouldn’t see these, and the Satsuki would flower sparsely next year. 

It’s also a good time to assess how the timing of decandling and summer fertilizing of Japanese Black Pine went. Even if the decandling timing was right, without some fertilizer during the summer we may not get reasonable needle length in the regrowth. These needles are about right, 1 1/2” for a medium-sized tree. Now we increase fertilizing as fall advances to set the buds up well for spring decandling. Spring decandling success is highly dependent on the energy of the buds the previous fall. 

Though short needles seem nice, these Japanese Black Pine needles are too short for a medium-sized tree, and could have used more fertilizer during the summer, or the candles could have been cut a couple weeks earlier.

October a good time to prune almost anything. Pruning sets up remaining buds well for spring. After a trim on the red marks on this Vine Maple, fertilize. Fall is an excellent time to fertilize well, including with nitrogen—there’s a chapter in Bonsai Heresy that explains why some nitrogen is important for bedtime.

Alder after a shoot trim. Buds can be seen forming in the axils of the petioles, ready for next spring. If cut too late in the fall, or even into the winter, this chance at bud activation is lost.

Although others may use different terms, I consider pruning a big cut with a tool like a concave pruner (left), and trimming is cutting a shoot with a bud scissors (right). Fall is a good time to do both.

Scots pine with a strong shoot with big buds. If in development, maybe leave alone to help build trunk and branches and roots. If in refinement, consider trimming this off at the red mark and leaving the smaller shoots below it. 

Another fork in the road with technique chosen based on tree development. This is Kishu Shinpaku with long shoots. If you’re still building the design and need branch length, consider leaving and wiring (we can wire just about anything in fall, though maybe wait until deciduous are just out of leaf). If the tree’s branch structure is set, then trim at red marks and the remaining shoots will fluff up into those lovely clouds that make juniper such a favorite for bonsai.

A Rocky Mountain Juniper with extensions. Rocky makes many more extensions than Shinpaku, even late into refinement. About twice a year these need to be trimmed at the red marks, just inside the canopy of the foliage. This redistributes the energy and over time it evens out, the pads get denser, and the extensions get shorter. This selective scissor trim is the same technique for Hinoki, Cypress, and Cryptomeria. 

Another job for fall is taking off unwanted fruit. This is a Dwarf Japanese Quince, ‘Chojubai’. If left on, resources that could have gone to bud development for next year are put into the fruit.

This Harland Boxwood grew late into the early fall—as is common with subtropicals in my temperate climate—and we’ll keep an eye on the soft growth and protect it early before any convincing cold sets in. 

A few more thoughts:

• single flush pines may be wired now (since mid-summer), but decandled black pines may still be growing their needles, which are soft and are easily broken when wiring
• in many areas it rains more in the fall, so at this time a slow-release fertilizer may be desired as you won’t be watering as much—and rain can leach in solid fertilizer rather than flushing out liquid fertilizer
• depending on climate, it’s also a good time to get a game plan for winter cold—prepare for the worst storm, not the average storm
• check for tight wire—early fall is a good time to catch any that you missed earlier