If the flower has been pollinated successfully, a slender green seed pod will develop from the ovary at the base of the flower:
Under normal conditions, when the seed is mature the outer capsule will dry off, turning brown before it splits open before it splits open (dehiscence) and releases the small wind-: dispersed seeds.
Conditions for germination
Tillandsias need warmth, moisture and light to germinate, just as all the rest of the bromeliads do. Only trouble is, most Tillandsias will soon die if they are sown on the ground! So they need to be sown on something hanging up in the air. Early growers used to germinate then in the greenhouse on a small bundle of twigs (usually Thuja, or some other Cypress, but I used Macrocarpa or any old conifer with no apparent loss of performance. The general idea of using Cypress was because there is something there which inhibits growth of algae, a problem because Tillandsia seed are so slow.)
Sowing seeds on sticks or ponga (tree fern), or small strips of plastic mesh such as shadecloth) in the glasshouse is ok when seed is fresh, and during the summer if they are kept relatively shaded and moist. But you can have difficulty starting them off during winter or with imported seed, because viability decreases rapidly.
I have found that seed and seedlings need a lot higher humidty than used to be thought.
For best results, you need to give the seeds;
Around 20-25oC during the daylight hours, and a little drop at night by about 5oC.
About 14 hours of light per day.
Humidity 80-90%, dropping back to 60-70% when ventilation is increased slightly when they get to the stage of having two distinct leaves formed.
Water if possible by spraying every 3-4 hours for the first 3-4 days, then once each night and evening. Once they have germinated, they must be allowed to dry between watering.
How do you accomplish this? My first device was built around a 2 x 40 watt fluorescent fitting, in the form of a wooden frame 4ft long, 18"deep and 2ft high made of 2” x ½” timber and covered by a couple of layers of PVC sheeting with flaps at the ends which I rolled up during the day to let them get fresh air. The fluorescent tubes were at the top (of course!) and immediately beneath them was a layer of chicken wire.
The seeds were sown on small strips of shadecloth (say 6" x 1") hung from the chicken wire on little hooks. On the floor was a tray with a soil warming cable in it, and by increasing and decreasing the amount of water in the sand I control the humidity. I found that opening the flaps gave too much ventilation (lowered the humidity too much), and I also found that I had to cover the whole thing with a woolen blanket during the winter to keep the temperature up.
Now I have a slightly larger incubator, made of solid timber. You need to have some air exchange going on—I have left about a ¼" gap aound the ballast of the fluorescent tube (I have the ballast sticking up out of the top, and the reflector screwed to the underside of the roof). During the first few weeks I leave the door shut, and the humidity is 100% (so it effectively rains in there just about), then after several weeks I start ventilating a little by leaving the front cover up about a half inch. Seed is sown on insect mesh.
Of course you don't have to go to all this trouble. There are much simpler methods - for example you could start the seeds off by enclosing them, on their mount, in a plastic bag hung in a warm place with bright indoor light. I used to do this, and in cold winter months just sat the seedling sticks, in their plastic bags, on a low-heat germinating tray.
I water with a small pressure sprayer, which I leave in the incubator to keep the water at "room temperature," and I reduce the pH to 6.0 with phosphoric acid. I don't think you have to do this, though, but they do prefer water on the the acid side. As I mentioned, when seeds are first sown I water them every 3 hours for a couple of days, then go back to morning and night sprays.
I grow seeds on in a greenhouse, minimum night temperature 7-8oC, under two layers of 35% shadecloth (in addition to normal greenhouse shading) then after a year or two start moving them out into progressively less shade. But I never take them out of the incubator between March and October (that would be around November to April in the northern hemisphere) because it is too cold and the days are too short for the juvenile seedlings.
Seedlings are transplanted onto community sticks when they are about 5-10mm high, 3-4 years old. They are glued with a water-resistant aliphatic glue, or Weldbond "Universal Space Age Adhesive" which is our current favourite! Some growers use a hot glue gun, which is fine.