Germinating the seeds
Puya is easy to germinate. Use small containers that have drainage holes. A well-draining soil is necessary, such as cactus soil. You may make your own mix with 1 part potting soil and 1 part perlite or coarse sand. An alternate mix is 1 part coir fiber to 2 parts perlite, with some slow-release fertilizer mixed in.
Fill each container and water it so that it is uniformly moist. Place 1 or 2 seeds on top, and sprinkle a very thin layer of soil on top - just enough to barely cover the seeds, because the seeds need some light to germinate. Drip a few drops of water over the seeds.
Until the seeds sprout, ensure that the surface soil never dries out. An easy way to to maintain moisture is to enclose the pots in a plastic dome or bag. Just leave it open a crack for some fresh air to enter. You may need to drip a few drops of water over them each day.
The seeds germinate well between 65-74 degrees F (18-24°C). I have no information about how they will sprout outside that temperature range. Germination might decline if the temperature gets too hot. I recommend placing a minimum/maximum thermometer near the pots.
Keep the pots in bright light away from direct sun. A fluorescent bulb kept 5 inches (12 cm) away provides the right amount of light.
Many of the seeds should sprout within 4 weeks, but allow up to 8 weeks for any slow ones. Continue keeping the surface soil moist until the seedlings have their second set of leaves - then you may let the surface dry out between waterings.
Once the seedlings have their third set of leaves, you may give them some morning sun. Transition them to stronger lighting gradually, and protect them from strong sun the first 2-3 months. After about 10-12 months they should be ready for full sun, except in hotter climates.
Long-term care: Feed about every 2-3 months with a slow-release (pelleted or organic) fertilizer. If your potting soil contains fertilizer (check the package) your seedlings shouldn't need feeding the first month.
While the plants are fairly drought tolerant, they grow the fastest when given adequate water, so avoid letting the soil completely dry out. Don't let the pots sit in a tray of water. If you are in a heavy rainfall area, use extra perlite, pumice or coarse sand in your mix.
Repot your plants to a larger container whenever necessary. Protect your plants from frost the first winter or two. Also keep them fairly dry during the winter, unless temperatures are above freezing. In very hot conditions, some afternoon shade is a good idea.
By the way, the leaves will develop a white powder on them. This is normal!
Have fun growing them!
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