I am going to offer an exceptionally un-helpful answer: It depends on the stature of the plant in general. I have plants that have been in a 4" pot for a couple years, and bloom like gangbusters, but aren't more than 12" high, and others nearly twice that big. I do think they like to be a little potbound to bloom, though.

HTH,

Celene

At our chapter meeting today, a new member brought in some streps he rooted from leaves in June. They had leaves about four inches long and had their first flowers. They were not minis but were typical of the varieties we see today. I think they were 'Magentosphere', a speckled netted purple.

Patrick,

It depends on the variety. The crown generally needs to grow to a certain size before blooming. And as mentioned, they like to be potbound.

I have found that they bloom much quicker if you remove the immature leaves on the plant. Once I left the leaf there for a long time and the plant never seemed to bloom. The sooner I remove them, the faster they bloom. This may be because the immature leaf does not make blooms and when you remove it more energy goes to growing leaves that do have the ability to bloom. Now I remove the immature leaves as soon as possable.
-renee

Renee,

I forgot about that. I usually clip one of the leaves of the first crown when it gets more than four inches long. This stimulates the growth of a new crown which is more likely to bloom.

But I do find that I get blooms on the first crown, but haven't noticed why some do and some don't.

I have a few plants with two 4 inch leaves with its first bloom.

I think it depends on:
1. The season: everything blooms in spring and seems to decline in the fall.
2. Your culture, humidity, fertilizer or not, other aspects of culture.
3. Variety. Some bloom more frequently and stay longer than others.
4. Good luck.

Nancy

I agree with Nancy on all accounts. It depends on all of those things. I just got some lovely little starts, one of them is Museum of Art which I am very eager to see bloom. It's longest leaf is just about 3 inches, but it already has a bud. Most of the ones I have gotten have been in bud when I received them. They came from warm, well-lit, highly humid environments where they were well-fertilized, so even though they were quite small, they were ready to bloom.