Begonia seedlings are not growing. Why not?

last year

I'm trying to grow begonias (fibrous) from seed. Last year, I used non pelleted seeds and none germinated. This year, I used pelleted seeds. I planted them on 2024-12-28 and after 14 days, they had nearly all germinated. They are in cells in trays in my basement under grow lights. Today is 2025-02-05 and they're only 1/8" tall. At this rate, they'll be 1/2" tall by mid-May when it's time to transplant them to the garden. That's not gonna work. I'll have to throw them all out and go out and buy Begonia plants. I've fertilized them twice (Jan 23 and Feb 2) with 1/8 tsp of 24-8-16 in a gallon of water. That didn't seem to help. They are planted in Jiffy Seed Starting Mix.

What am I doing wrong? What should I do to get them to grow faster?

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Comments (3)

hc mcdole
last year
The pink-purple lighting doesn't help seeing the seedlings. That is beside the point.

What I've heard and read over the years is to move your seedlings to a new media when they develop their first true leaves (or anytime after the cotyledons are replaced by true leaves). As for fertilizer, be careful with young seedlings. It sounds like you haven't had any issues with that, though.

Are you using a humidity lid/enclosure for the time being? That will help move them along as well.

Here is a tray I did last year of a weedy wax begonia seedlings and mixed cuttings of other begonias. The ferns are all volunteers (I guess their spores carry in the air like algae).

This is a tray of Jiffy pellets (72 to a tray) and makes it so easy to sow or cut, but I am too lazy to move them up a lot of the time.
HU-732245899
Original Author
last year
Thanks, mcdole. I moved the seedlings to clean cells that contain Miracle Grow potting soil. Also, I put a clear plastic dome over the cells. I did these two things 4 days ago. Today, they look fine. So, I guess they survived the transplanting.
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hc mcdole
last year
I hope it all goes well on your seedling trials. Hang in there!

Here are some I transplanted months ago (I had them in a Jiffy pellet for months - progress is slow in my neck of the basement).

This is two of them. The Primulina has a lot of offshoots. The small begonia better start growing to beat the creep and crawl of the Primulina.

Some more shots. Lots of algae growing in this tray.

closer up (the pink Episcia is spreading as well)