Growing cacti and succulents from seed is relatively straightforward and can produce a diverse collection of plants in only a few years. More than 2,000 species of cacti and succulents are suitable as tabletop potted plants or tall floor plants. The seeds are generally available from commercial seed companies.
1. Clean propagation pots by washing them with disinfectant. Pots should be small and shallow, no more than 4 inches (10 cm) deep and 6 inches (15 cm) in diameter. There are many different suggested growing media formulas to experiment with. One recipe calls for mixing a coarsely sifted organic growing medium, such as commercial potting soil, with an equal volume of sharp sand, perlite, or pumice for drainage.
2. Pasteurize your growing medium by baking it in an oven at 300 °F (150 °C) for 30 minutes. Allow it to cool and wet it thoroughly. Let it drain but not dry out. Fill the pots with the moist soil mixture to about 0.5 inches (1.2 cm) below the rim.
3. Sow seeds in the pots around the end of spring. Plant seeds as deep into the soil as the seeds are wide and press down lightly. Cover small seeds with a sprinkling of sand to hold them in place. Seed spacing will depend on the species of cactus or succulent you are germinating. Cover the pots with clear plastic or glass. Place them in a bright location but out of the direct sun. Keep the temperature around 70 °F (21 °C). If the soil seems too dry, spray lightly with water. Be sparing. Too much water can drown the seed. Do not let the soil dry out.
4. Watch for germination. Most cacti and succulents will germinate within three weeks, but some species require more time, up to a year. When seedlings appear, raise the cover during the day for ventilation. Watch soil moisture. Do not allow the soil to dry out but also do not saturate it. Keep the temperature between 50 and 70 °F (10 and 21 °C).
5. Transplant your plants into their permanent pots. Most cacti and succulents will be ready to transplant in 6 months to a year after germination. The right growth size for transplanting will depend on the species you are growing. Most cacti can be transplanted when they are the size of a large marble. Many other succulents may be transplanted when they are 2 to 4 inches (5 to 10 cm) tall. Gently lift the plants from the growing medium, set them into the soil of the new pot, firm the soil around the roots, and water well.