AusBonsai

Is there a general rule of thumb for when to stop trimming a tree in order for it to flower? Examples would be azalea, crepe myrtle, prunus, sannantha, melaleuca, blue berry ash . . .
My guess is about 4 months, but suspect it will vary by species and climate.

I think it is longer than 4 months. I have not done enough trials to give a personal view but I seem to remember someone saying March for azaleas that will flower October/Nov.
I've been leaving my Callistemons after pruning in Dec for flowering the following Nov. They grow a bit long but do flower.

Anyone with a better grasp on this?

Satsuki Azaleas need to be trimmed by late Jan/early Fed if you want flowers Oct/Nov later that that you are removing the potential flowers.
I think the timing is more like 7-8-9 months. Punus prune around Dec for flowers in Spring from memory.
Wisteria develop their flowers Jan-Feb for Spring Flowers as another example. So definitely more than 4 months.
Cheers
Kirky

I usually heavy prune straight after flowering and then leave until next flowering if i am not developing the tree and want good flowering.

I usually heavy prune straight after flowering and then leave until next flowering if i am not developing the tree and want good flowering.

Reckon that's as good as advice as you'll get, since your conditions and climates are likely to be very different from the climates and conditions your advice is coming from.

I'll pinch my crepe myrtle back twice before I let it run to flower - pinch back to two leaves when there are six or eight on the new shoot.

I'll prune Prunus back twice at least in the season, last one might be January/February? down here - so long as they get a chance to set up a 6-8 leaf branchlet before the leaves drop they'll flower. Similar with crab apple, but I must admit I haven't been so particular with that.

Citrus are variable, but a number flower in spring, right after you've just cut the flowering buds off...

Callistemon/Mel: I think Pup had something on them, maybe pinch/cut back once or twice then leave them go? NBPCA or Grant could confirm what the do at the Collection.

I don't get flowers on my Leptos or Kunzeas because I keep them in the "grow long cut back hard" cycle that mainly encourages foliage (and trunk thickening) - they're still young. If you find out when they flower and count back six months, you could probably start experimenting from there.

One Banksia serrata at the NBPCA sneaks out a flower or two each year because a weak inward-growing shoot hidden somewhere doesn't get pinched - the other Banksias don't seem to do this.

Eucs forget about it.

There aren't enough flowering bonsai for my money.

Gavin

Lots of good experience in those replies. Looks like I was a bit out with March as latest to cut Azaleas, Thanks Kirky. I think I trimmed my azaleas in Jan so for flowers in spring.

We do need to differentiate between the classes of flowering plants:
1. Spring flowers on last year's shoots eg Callistemon, azalea, prunus, wisteria, etc. Definitely appears that flower buds are initiated by the end of summer for most of these spring flowering plants.
2. Spring flowers on fruiting spurs eg apple pear, and crabapple. These form permanent short shoots that flower year after year so once these spurs appear they will flower despite the long shoots being pruned which means you can prune any time.
3. Summer flowering on current growth eg Crepe myrtle. Allow spring shoots to grow and flower then prune hard after flowering, though as Gavin points out you can get away with one or 2 early cuts and still get enough growth for flowers later in summer.

Can anyone add any other broad classes of flowering bonsai?

I have three large-leaf crepe myrtles, they all have completely different growing habits. All three were clipped back to two or three leaves right through Spring, up til the last day in Oct last year.

The one in the smaller pot, with restricted root run, didn't produce any flowering shoots until I left a long sacrifice branch to grow from the base of the trunk. It flowered a month after the other two. The lilac one grew stalks over a metre long and it flowered in December. The pink one grew 30cm long stalks and flowered profusely in December. After the lilac and pink had finished, I cut back hard, and blow me down if they didn't both start throwing new flowering stalks. The lilac one threw much shorter shoots and the flowers were definitely smaller too, the pink one was a mass of flowers again all through Jan and Feb. It still has new flowers coming.

This is why I suggest that whatever you're told, don't expect it to be set in stone. You have to find out what your plants are going to do in your climate, and try to keep notes so you know how best to keep them doing what you want. Crepe myrtles can be ornery baskets....