How to Propagate a Cactus From Seed

Fill a 2-, 3- or 4-inch planting pot three-quarters of the way with well-draining cactus soil, available from garden centers and nurseries. This material reduces the chance of mold growth and provides adequate nutrition for the germinating seeds.

Gently flatten the soil with your fingers, then spread the cactus seeds over top of the soil. You may plant multiple seeds in a single pot as long as space them at least 1/8 inch apart.

Cover the seeds with a layer of 1/8 inch to 1/4 inch of fine sand. The sand should permit some light through, but will protect the seeds from any temperature changes or harsh light exposure.

Place the planting pot in a bowl of water, so that the soil absorbs water through the drainage holes. Keep the pot in place until you can feel the moisture at the top of the soil. Lift the pot and allow excess water to drain away.

Cover the top of the pot with a clear plastic bag or clear plastic wrap. Store the pot in an area that receives bright, indirect sunlight for most of the day. Direct sunlight may burn the leaves, so be careful. Depending on the type of cactus you are growing, seeds will germinate in two weeks to four months.

Remove the plastic from the top of the pot when the seedlings are in danger of touching it; the plastic can suffocate budding plants. Keep the cactus in filtered light only for at least a year to avoid burning.

Keep the soil consistently moist at all times. Once the seedlings are at least 2 inches tall you may begin pouring water into the pot instead of watering from below.