Sowing theSeeds
For an ideal cactus seedling mix, combine and sterilize the following:
- 25% Crushed granite
- 25% Crushed limestone
- 10% Perlite
- 40% Screened aged compost, screened potting mix, or screened cactus mix
Use a clear-domed, double-layer nursery tray, found at most hardware stores. The bottom tray should have channels to permit brief bottom-soaking and drainage. Fill each cell to just beneath the top with the sterilized and cooled soil mix; don't tamp down. Fill the bottom tray with 1" of water; soak nursery tray for 20 minutes until substrate is moist. Drain lower tray, replace cell tray. Surface-sow seeds 1-2 per cell, mist with a hand sprayer, and replace the dome.
Place the trays on a heat mat set between 70F° and 75°F with a 100-watt (minimum) fluorescent plant light 8" to 10" above the trays. Or, place them in a sunny window in a room that doesn't fall below 65F°. Your baby cacti will require 8-12 hours of light each day. Mist-soak them daily, but watch out for algae and fungus. Removing the dome for an hour or so a day will let the trays "breathe".
Growing Conditions
Most cacti, including the species in our mixture, do not tolerate frost. Potted cacti can be brought indoors in wintertime, provided they're given plenty of artificial sunlight or a sunny spot near a window. Humidity helps them germinate but once they're established, young cacti prefer hot, arid climates. While they can withstand drought, they don't tolerate standing water; completely drench their substrate when the top 1" to 2" inches is dry to the touch.
Cactus roots are shallow to take advantage of rare, brief rains. Wide, shallow containers work great, especially for multi-species plantings. Feed with a quality cactus fertilizer 2-3 times each year.
If you wish to transplant your cacti outdoors (in no-frost areas only) amend the planting spot with a mix similar to that described above. Choose a site with 8-10 hours of direct sunlight, and take care to follow watering guidelines.
Germination & Growth
Cacti species germinate at different rates, and cultivation conditions further influence emergence. Expect tiny bright green "blobs" to poke up from the plant surface in about 7-12 days, but don't give up on them until 30 days has passed.
If you get two or more baby cacti in a cell, separate them with pebbles or small rocks to shape a "tiny cactus garden". Or, you can gently transplant them to their own cells. Cacti can learn to cohabitate when they're grown in containers.
