Cacti are fascinating plants, available in a variety of unusual shapes and sizes and a rainbow of colors. Cacti have very specific needs regarding temperature, light and water, which makes growing cactus from seed a trial and error process. Although it may be easier to purchase cactus that are already growing, planting your own cactus from seeds can be rewarding.
Sift enough cactus potting soil to fill the 2-inch pots, and be sure any lumps of soil are removed. Set the pots in a saucer of water but remove them as soon as the water seeps to the top of the soil.
Sprinkle a few seeds on top of the soil, leaving at least 1/2 inch between each seed to avoid overcrowding. If the cactus seeds are tiny, you might find it easier to mix them with a small amount of sand.
Cover each pot with a piece of clear plastic and secure it with a rubber band. Poke a few small holes in the plastic for ventilation. The plastic will help to keep the soil moist, but if you notice that it's drying out, moisten it with a mister.
Place the pots under a grow light, leaving about 6 to 9 inches between the light and the top of the soil. If may be helpful to put the grow light on a timer, because the cactus seeds should be under the light for 14 to 16 hours each day.
Warm the pots on a heating pad during the daylight hours and remove the pots from the heating pad at night. While the seeds are germinating, they should be kept between 75 and 90 degrees F. The heating pad can be placed on a timer along with the grow light.
Remove the plastic when the seeds germinate, which will take at least a week. Leave them under the grow light, but as long as they're in a fairly warm room, it's safe to remove the heating pad at this time. Continue to mist them every day until the cacti are a few weeks old. At that time, they should be watered once every 2 to 3 weeks.