|I have bought a lot of gladiolus and watsonia seeds from South Africa.
Does anybody have expérience of growing gladiolus from seeds ?
I have expérience of germination bulb seeds from my country, but I don't know the germination température for gladiolus and watsonia .
When is it the best time for germination ?
I’ve planted spring germinators that did just fine at room temperature under fluorescent lights. I think nights were always between 67 F and 71 F, whereas daytime temperatures were generally 75 F to 80 F. I kept them in a window with some morning sun and didn’t worry about light bulb color (warm white, cool white, etc.).
I don't recall germinating any South African that were marked as fall germinators (Sow Au.). If I tried some of them now I would opt for cooler night temperatures (50 F to 60 F), but I'm not sure it matters. I think the main thing for autumn germination is short days (just guessing). So, I would make sure not to give too long a day with artificial light, no more than 12-13 hours. If you get some that will not germinate, try them with night temperatures lower than 50 F. You can let the pots dry and then try them a month or two later, or you can merely adjust temperatures so that the night is cooler.
Germination was mostly successful, but I killed a whole lot of plants post-germination. I put them out in early spring, in their small seeds pots (2 inch) and they were doing very well. However, I neglected them during a hot spell of about 3 days and many died. The heat did not kill them (80 F), it was the lack of water and their tiny roots. I think they would have done better in larger (deeper) pots so they would have had a better reserve of moisture.
This year I am trying something new for seed germination. I used the method last year for native azaleas (USA Rhododendron spp.) and had good success. The basic thing is to put ½ inch to 1 inch pure perlite in the bottom of the seed pot. The azalea roots hit the perlite and self prune. It seemed to cause better branching. But, it also kept the roots above the very bottom of the pot where any excess water accumulated. Finally, it seemed to provide better aeration for the soil because the perlite held air spaces.
This year I’m using the perlite method with Aloe, Crassula, and Agave species (no bulbs) but am also using deeper pots—I’m using 12-16 ounce, inexpensive drinking cups (Soho or Dixie Brand). They can be a little top heavy because of their shape but sure do provide a nice deep pot. Finally, I’m using the same soil mix that worked well for the bulb seeds last year. It is 50% humus (no peat moss), 25% coarse sand, 25% perlite. Peat moss might work for you, but I can’t stand the fungus gnats that always find a way into the house.
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